From 3b1eb338e61c6ef8223a9f0d123d390289fa6e49 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@users.noreply.github.com>
Date: Mon, 29 Jan 2024 09:08:26 +0100
Subject: [PATCH] Binding System refactor (#13970)

* Update ncrunch config.

* WIP: Benchmarks

* Initial refactor of binding infrastructure.

- `ExpressionObserver` has been removed and its functionality merged with `BindingExpression`
- `BindingExpression` handles all types of `BindingMode` itself; doesn't require `BindingOperations.Apply` to set up a separate observable for `TwoWay/`OneWayToSource` bindings
  - This allows us to fix some long-standing issues with `OneWayToSource` bindings
- Expression nodes have been refactored
  - No longer split between `Avalonia.Base` and `Avalonia.Markup`
  - Categorize them according to whether they use reflection or not

A few tests are failing around binding warnings: this is because the next step here is to fix binding warnings.

* Make default binding Source = UnsetProperty.

Null is a theoretically valid value for `Source`; setting it to null shouldn't mean "use the data context".

* Move logging to BindingExpression.

As `BindingExpression` now has enough information to decide when it's appropriate to log an error/warning or not.

Fixes #5762
Fixes #9422

* Add compatibility hack for older compiled bindings.

Previously, `CompiledBindingPathBuilder` didn't have a `TemplatedParent` method and instead the XAML compiler rewrite templated parent bindings to be a `$self.TemplateParent` property binding. resulting in extraneous logs.

Add a constructor with an  `apiVersion`  to `CompiledBindingPathBuilder` which will be used by newer versions of the XAML compiler, and if a usage is detected using an `apiVersion` of 0, then upgrade `$self.TemplatedParent` to use a `TemplatedParentPathElement`.

* Log errors from property accessors.

* Don't log errors for named control bindings...

...on elements which aren't yet rooted.

* Log errors for failed conversions.

* Use consistent wording for binding warnings.

"Could not convert" instead of "Cannot convert".

* Log warnings for converter exceptions.

* Don't convert new TargetTypeConverters each time.

* Added failing test for implicit conversion.

* Support cast operators in compiled bindings.

A bit of a hack as we'd ideally not be using reflection when using compiled bindings.

* This shouldn't be a public API.

Should only be used for tests.

* Make enum/int conversion work.

* Check for SetValue equality after conversion.

And also use "identity equals" where value types and strings use `object.Equals` and reference types use `object.ReferenceEquals`.

* Added ConverterCulture back to bindings.

* Fix merge error.

Removed deleted files from csproj that were re-added due to indentation changes.

* Use BindingExpression directly in ValueStoe.

* Introduce BindingExpressionBase.

And `UntypedBindingExpressionBase`.

* Make TemplateBinding a BindingExpression.

* Make DynamicResource use a BindingExpression.

* WIP: Start exposing a BindingExpression API.

* Finish exposing a BindingExpression API.

* Fix OneTimeBinding.

* Remove unneeded classes/methods.

* Don't call obsolete API.

* Make BindingExpressionBase the public API.

This matches WPF's API.

* Added BindingExpressionBase.UpdateTarget.

* Initial implementation of UpdateSourceTrigger.

* Don't use weak references for values.

If they're boxed values, they can get collected.

* No need for virtual/generic methods here now.

* Reintroduce support for binding anchors.

Turns out these were needed by animations, just our animation system has no unit tests so I missed that fact earlier. Add a basic animation unit test that fails without anchor support, and add binding anchors back in. Currently a private API as I suspect this feature shouldn't be needed outside the framework.

* Include new property in clone.

And add real-life example of `UpdateSourceTrigger=LostFocus` to BindingDemo.

* Fix merge error.

* Updated BindingExpression tests.

- Make them run for both compiled and reflection bindings (found a bunch of tests that fail with compiled bindings)
- Make them not depend on converting the `BindingExpression` to an observable and instead test the end result of the binding on an `AvaloniaObject`

* Fix compiled binding indexer tests.

* Use data validation plugins in PropertyAccessorNode.

Added a warning suppression for now: we may need a separate `DataValidators` list for AOT-friendly plugins.

* Don't separate plugins by reflection.

`DataAnnotationsValidationPlugin` is public and so it can't be moved. No point in moving the others if this one will be in the wrong place.

* Remove unneeded methods.

* Make reflection binding tests use a string.

Convert the `System.Linq.Expression` to a string and then use this, as reflection bindings will always be instanced with a string path.

* Added TODO12 plan for IBinding2.

* Use more specific exception.

* Fix nits from code review.

* Make expression nodes sealed where possible.

* Unsubscribe on Stop, don't re-subscribe.

D'oh.

* Tweak ExpressionNode lists.

Saves a few K in benchmarks and it's a cleaner API.

* Add a pooled option in BindingExpressionGrammar.

Micro-optimization.

* Avoid allocations when enumerating binding plugins.

* Add IBinding2 support to observable bind overloads.

In the case of `TemplateBinding`, the `IObservable<object?>` bind overload is selected by C#. Add an explicit check for an `IBinding2` here to use the more performant code-path.

* Remove disposed binding from ImmediateBindingFrame.

* Added TemplateBinding benchmarks.

* Remove duplicate items.

Seems to have been caused by a merge error.

* Fix exception when closing color picker.

And add tests.

* Don't skip converter when binding to self.

* Don't pass UnsetValue to converters.

This follows WPF behavior.

* Log element name if present.

More useful than just logging the control hash code.

* Respect binding priority.

* Throw on mismatched binding priorities.

We don't want to respect the binding priority in this case as it breaks `TemplateBindings` when the default `LocalValue` priority is passed. Instead make sure that the priority parameter matches that of the expression.

This reverts commit a72765d70514506d94b39ba33a3d91e11cd6dcd4.

* Convert to target type in TemplateBinding.

* Short-circuit target type conversion for same types.
---
 .ncrunch/Avalonia.Tizen.v3.ncrunchproject     |   5 +
 .../ControlCatalog.Tizen.v3.ncrunchproject    |   5 +
 .ncrunch/ControlCatalog.v3.ncrunchproject     |   5 +
 .ncrunch/PInvoke.net6.0.v3.ncrunchproject     |   5 +
 .../PInvoke.netstandard2.0.v3.ncrunchproject  |   5 +
 samples/BindingDemo/MainWindow.xaml           |   1 +
 .../Animation/AnimatorKeyFrame.cs             |   4 +-
 src/Avalonia.Base/AvaloniaObject.cs           |  84 +-
 src/Avalonia.Base/AvaloniaObjectExtensions.cs |  29 +-
 src/Avalonia.Base/AvaloniaProperty.cs         |   8 +
 src/Avalonia.Base/ClassBindingManager.cs      |   2 +-
 .../Data/BindingChainException.cs             |  12 +-
 .../Data/BindingExpressionBase.cs             |  55 ++
 src/Avalonia.Base/Data/BindingNotification.cs |  41 +
 src/Avalonia.Base/Data/BindingOperations.cs   |  34 +-
 src/Avalonia.Base/Data/BindingValue.cs        |  39 +
 .../Data/Core/AvaloniaPropertyAccessorNode.cs |  57 --
 src/Avalonia.Base/Data/Core/BindingError.cs   |  18 +
 .../Data/Core/BindingExpression.cs            | 906 +++++++++++-------
 .../Data/Core/EmptyExpressionNode.cs          |   7 -
 src/Avalonia.Base/Data/Core/ExpressionNode.cs | 168 ----
 .../Core/ExpressionNodes/ArrayIndexerNode.cs  |  54 ++
 .../AvaloniaPropertyAccessorNode.cs           |  58 ++
 .../ExpressionNodes/CollectionNodeBase.cs     |  81 ++
 .../Core/ExpressionNodes/DataContextNode.cs   |  31 +
 .../ExpressionNodes/DataContextNodeBase.cs    |  19 +
 .../Core/ExpressionNodes/ExpressionNode.cs    | 253 +++++
 .../Core/ExpressionNodes/FuncTransformNode.cs |  28 +
 .../ExpressionNodes/IPropertyAccessorNode.cs  |  13 +
 .../Core/ExpressionNodes/ISettableNode.cs     |  23 +
 .../LogicalAncestorElementNode.cs             |  85 ++
 .../Core/ExpressionNodes/LogicalNotNode.cs    |  69 ++
 .../Core/ExpressionNodes/MethodCommandNode.cs | 107 +++
 .../Core/ExpressionNodes/NamedElementNode.cs  |  46 +
 .../ExpressionNodes/ParentDataContextNode.cs  |  67 ++
 .../ExpressionNodes/PropertyAccessorNode.cs   |  85 ++
 .../DynamicPluginPropertyAccessorNode.cs      |  95 ++
 .../Reflection/DynamicPluginStreamNode.cs     |  53 +
 .../Reflection/ExpressionTreeIndexerNode.cs   |  81 ++
 .../Reflection/ReflectionIndexerNode.cs       | 159 +++
 .../Reflection/ReflectionTypeCastNode.cs      |  29 +
 .../Data/Core/ExpressionNodes/SourceNode.cs   |  26 +
 .../Data/Core/ExpressionNodes/StreamNode.cs   |  43 +
 .../ExpressionNodes/TemplatedParentNode.cs    |  49 +
 .../VisualAncestorElementNode.cs              |  86 ++
 .../Data/Core/ExpressionObserver.cs           | 316 ------
 src/Avalonia.Base/Data/Core/IBinding2.cs      |  20 +
 .../Data/Core/IBindingExpressionSink.cs       |  34 +
 src/Avalonia.Base/Data/Core/ITransformNode.cs |   7 -
 .../Data/Core/IndexerBindingExpression.cs     |  68 ++
 .../Data/Core/IndexerExpressionNode.cs        |  76 --
 .../Data/Core/IndexerNodeBase.cs              | 102 --
 src/Avalonia.Base/Data/Core/LogicalNotNode.cs |  91 --
 .../Data/Core/MarkupBindingChainException.cs  |  43 -
 .../Core/Parsers/BindingExpressionVisitor.cs  | 232 +++++
 .../Data/Core/Parsers/ExpressionTreeParser.cs |  26 -
 .../Parsers/ExpressionVisitorNodeBuilder.cs   | 219 -----
 .../Plugins/AvaloniaPropertyAccessorPlugin.cs |   4 -
 .../Data/Core/Plugins/BindingPlugins.cs       |  28 +-
 .../DataAnnotationsValidationPlugin.cs        |   3 +-
 .../Core/Plugins/ExceptionValidationPlugin.cs |   2 -
 .../Core/Plugins/IDataValidationPlugin.cs     |   5 +-
 .../Core/Plugins/IPropertyAccessorPlugin.cs   |   6 +-
 .../Data/Core/Plugins/IStreamPlugin.cs        |   3 -
 .../Core/Plugins/IndeiValidationPlugin.cs     |   3 -
 .../Plugins/InpcPropertyAccessorPlugin.cs     |  21 +-
 .../Data/Core/Plugins/MethodAccessorPlugin.cs | 157 +--
 .../Core/Plugins/ObservableStreamPlugin.cs    |   9 +-
 .../Core/Plugins/ObservableStreamPlugin`1.cs  |  27 +
 .../Plugins/PropertyInfoAccessorPlugin.cs     |  27 +
 .../Plugins/ReflectionMethodAccessorPlugin.cs | 141 +++
 .../Data/Core/Plugins/TaskStreamPlugin.cs     |   5 +-
 .../Data/Core/Plugins/TaskStreamPlugin`1.cs   |  49 +
 .../Data/Core/PropertyAccessorNode.cs         | 103 --
 src/Avalonia.Base/Data/Core/SettableNode.cs   |  53 -
 src/Avalonia.Base/Data/Core/StreamNode.cs     |  56 --
 .../Data/Core/TargetTypeConverter.cs          | 127 +++
 src/Avalonia.Base/Data/Core/TypeCastNode.cs   |  34 -
 .../Data/Core/UntypedBindingExpressionBase.cs | 600 ++++++++++++
 .../UntypedObservableBindingExpression.cs     |  34 +
 .../CultureInfoIetfLanguageTagConverter.cs    |   0
 src/Avalonia.Base/Data/IBinding.cs            |   3 +
 src/Avalonia.Base/Data/IndexerBinding.cs      |  18 +-
 src/Avalonia.Base/Data/InstancedBinding.cs    |  33 +-
 .../Data/TemplateBinding.Observable.cs        |  21 +
 src/Avalonia.Base/Data/TemplateBinding.cs     | 272 +++---
 src/Avalonia.Base/Data/UpdateSourceTrigger.cs |  29 +
 .../Diagnostics/ObsoletionMessages.cs         |  12 +
 src/Avalonia.Base/DirectProperty.cs           |   7 +-
 src/Avalonia.Base/DirectPropertyBase.cs       |   7 +
 src/Avalonia.Base/IDirectPropertyAccessor.cs  |   6 +
 src/Avalonia.Base/Logging/TraceLogSink.cs     |  37 +-
 src/Avalonia.Base/Properties/AssemblyInfo.cs  |   2 +
 .../PropertyStore/BindingEntryBase.cs         |   2 -
 .../PropertyStore/EffectiveValue.cs           |  12 +
 .../PropertyStore/EffectiveValue`1.cs         |  18 +-
 .../PropertyStore/ImmediateValueFrame.cs      |   7 +
 .../LocalValueBindingObserverBase.cs          |   2 -
 .../PropertyStore/LoggingUtils.cs             |  82 --
 .../PropertyStore/UntypedBindingEntry.cs      |  39 -
 .../PropertyStore/UntypedValueUtils.cs        |  18 -
 src/Avalonia.Base/PropertyStore/ValueFrame.cs |   1 +
 src/Avalonia.Base/PropertyStore/ValueStore.cs | 142 ++-
 src/Avalonia.Base/StyledProperty.cs           |  13 +-
 .../Styling/PropertySetterBindingInstance.cs  |  60 --
 src/Avalonia.Base/Styling/Setter.cs           |  25 +-
 src/Avalonia.Base/Utilities/TypeUtilities.cs  |  30 +-
 src/Avalonia.Base/Visual.cs                   |  20 -
 .../AutoCompleteBox/AutoCompleteBox.cs        |   2 +-
 .../XamlIlBindingPathHelper.cs                |  43 +-
 .../Avalonia.Markup.Xaml.csproj               |  99 +-
 .../Data/DynamicResourceExpression.cs         | 155 +++
 .../CompiledBindingExtension.cs               | 136 ++-
 .../CompiledBindings/ArrayElementPlugin.cs    |  72 --
 .../CompiledBindings/CommandAccessorPlugin.cs | 155 ---
 .../CompiledBindings/CompiledBindingPath.cs   |  90 +-
 .../FindVisualAncestorNode.cs                 |  53 -
 .../CompiledBindings/MethodAccessorPlugin.cs  |  73 --
 .../ObservableStreamPlugin.cs                 |  31 -
 .../PropertyInfoAccessorFactory.cs            |   5 +-
 .../PropertyInfoAccessorPlugin.cs             |  33 -
 .../CompiledBindings/StrongTypeCastNode.cs    |  18 -
 .../CompiledBindings/TaskStreamPlugin.cs      |   3 -
 .../DynamicResourceExtension.cs               |  39 +-
 .../ReflectionBindingExtension.cs             |   2 +-
 .../Templates/TreeDataTemplate.cs             |  10 +-
 src/Markup/Avalonia.Markup/Data/Binding.cs    | 194 ++--
 .../Avalonia.Markup/Data/BindingBase.cs       | 229 +----
 .../Avalonia.Markup/Data/MultiBinding.cs      |  52 +-
 .../Parsers/BindingExpressionGrammar.cs       |  26 +-
 .../Markup/Parsers/ExpressionNodeFactory.cs   | 145 +++
 .../Parsers/ExpressionObserverBuilder.cs      |  80 --
 .../Markup/Parsers/ExpressionParser.cs        | 139 ---
 .../Markup/Parsers/Nodes/ElementNameNode.cs   |  37 -
 .../Markup/Parsers/Nodes/FindAncestorNode.cs  |  53 -
 .../Markup/Parsers/Nodes/SelfNode.cs          |   9 -
 .../Markup/Parsers/Nodes/StringIndexerNode.cs | 317 ------
 .../Properties/AssemblyInfo.cs                |   3 +
 .../Animation/StyleAnimationTests.cs          | 124 +++
 .../AvaloniaObjectTests_Binding.cs            | 101 +-
 .../AvaloniaObjectTests_Direct.cs             |  31 -
 .../AvaloniaPropertyTests.cs                  |   1 +
 ...BindingExpressionTests.AttachedProperty.cs | 132 +++
 ...BindingExpressionTests.AvaloniaProperty.cs |  79 ++
 .../BindingExpressionTests.DataValidation.cs  | 361 +++++++
 .../Core/BindingExpressionTests.GetValue.cs   | 144 +++
 .../Core/BindingExpressionTests.Indexer.cs    | 299 ++++++
 .../Data/Core/BindingExpressionTests.Mode.cs  |  70 ++
 .../Core/BindingExpressionTests.Negation.cs   | 107 +++
 .../Core/BindingExpressionTests.Observable.cs |  89 ++
 .../Core/BindingExpressionTests.Property.cs   | 238 +++++
 .../Core/BindingExpressionTests.SetValue.cs   | 232 +++++
 .../Data/Core/BindingExpressionTests.Task.cs  | 128 +++
 ...dingExpressionTests.UpdateSourceTrigger.cs | 113 +++
 .../Data/Core/BindingExpressionTests.cs       | 665 +++++++------
 .../Core/BindingPathFromExpressionBuilder.cs  | 257 +++++
 ...ompiledBindingPathFromExpressionBuilder.cs | 314 ++++++
 ...xpressionObserverTests_AttachedProperty.cs | 125 ---
 ...xpressionObserverTests_AvaloniaProperty.cs |  86 --
 .../ExpressionObserverTests_DataValidation.cs | 227 -----
 .../ExpressionObserverTests_ExpressionTree.cs | 224 -----
 .../Core/ExpressionObserverTests_Indexer.cs   | 333 -------
 .../Core/ExpressionObserverTests_Lifetime.cs  | 112 ---
 .../Core/ExpressionObserverTests_Negation.cs  |  42 -
 .../ExpressionObserverTests_Observable.cs     | 199 ----
 .../Core/ExpressionObserverTests_Property.cs  | 738 --------------
 .../Core/ExpressionObserverTests_SetValue.cs  | 111 ---
 .../Data/Core/ExpressionObserverTests_Task.cs | 173 ----
 .../Plugins/ExceptionValidationPluginTests.cs |   1 -
 .../PropertyStore/ValueStoreTests_Frames.cs   |  18 +-
 .../Styling/SetterTests.cs                    |   9 +-
 .../Styling/StyleTests.cs                     |  23 +
 tests/Avalonia.Base.UnitTests/VisualTests.cs  |  49 -
 .../Avalonia.Benchmarks/Data/Binding_Setup.cs |  58 ++
 .../Data/Binding_Values.cs                    |  65 ++
 .../Data/BindingsBenchmark.cs                 |  59 --
 .../Data/PropertyAccessorBenchmarks.cs        |   2 +-
 .../Data/PropertyAccessorPluginBenchmarks.cs  |   4 +-
 .../Data/TemplateBinding_Setup.cs             |  46 +
 .../Data/TemplateBinding_Values.cs            |  50 +
 .../TreeViewTests.cs                          |  24 +-
 ...rverTests.cs => BindingExpressionTests.cs} |  32 +-
 .../Data/BindingTests.cs                      | 113 +--
 .../Data/BindingTests_Converters.cs           |  73 +-
 .../Data/BindingTests_Logging.cs              | 490 ++++++++++
 .../Data/TemplateBindingTests.cs              |  20 +
 ...> BindingExpressionGrammarTests_Errors.cs} |  28 +-
 ...onObserverBuilderTests_AttachedProperty.cs |  32 +-
 ...onObserverBuilderTests_AvaloniaProperty.cs |  16 +-
 .../ExpressionObserverBuilderTests_Indexer.cs | 122 ++-
 .../ExpressionObserverBuilderTests_Method.cs  |  17 +-
 ...ExpressionObserverBuilderTests_Negation.cs |  69 +-
 ...ExpressionObserverBuilderTests_Property.cs |  67 +-
 ...ilderTests.cs => ExpressionPathParsing.cs} |  86 +-
 .../Data/BindingTests_TemplatedParent.cs      |  34 +
 .../MarkupExtensions/BindingExtensionTests.cs |   1 -
 .../CompiledBindingExtensionTests.cs          | 116 ++-
 .../DynamicResourceExtensionTests.cs          |  28 +
 .../Xaml/BindingTests_RelativeSource.cs       |  19 -
 .../Xaml/ControlBindingTests.cs               |  38 -
 .../Xaml/ControlThemeTests.cs                 |  30 +
 201 files changed, 9573 insertions(+), 7203 deletions(-)
 create mode 100644 .ncrunch/Avalonia.Tizen.v3.ncrunchproject
 create mode 100644 .ncrunch/ControlCatalog.Tizen.v3.ncrunchproject
 create mode 100644 .ncrunch/ControlCatalog.v3.ncrunchproject
 create mode 100644 .ncrunch/PInvoke.net6.0.v3.ncrunchproject
 create mode 100644 .ncrunch/PInvoke.netstandard2.0.v3.ncrunchproject
 create mode 100644 src/Avalonia.Base/Data/BindingExpressionBase.cs
 delete mode 100644 src/Avalonia.Base/Data/Core/AvaloniaPropertyAccessorNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/BindingError.cs
 delete mode 100644 src/Avalonia.Base/Data/Core/EmptyExpressionNode.cs
 delete mode 100644 src/Avalonia.Base/Data/Core/ExpressionNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/ArrayIndexerNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/AvaloniaPropertyAccessorNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/CollectionNodeBase.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/DataContextNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/DataContextNodeBase.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/ExpressionNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/FuncTransformNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/IPropertyAccessorNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/ISettableNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/LogicalAncestorElementNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/LogicalNotNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/MethodCommandNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/NamedElementNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/ParentDataContextNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/PropertyAccessorNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/DynamicPluginPropertyAccessorNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/DynamicPluginStreamNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/ExpressionTreeIndexerNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/ReflectionIndexerNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/ReflectionTypeCastNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/SourceNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/StreamNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/TemplatedParentNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/ExpressionNodes/VisualAncestorElementNode.cs
 delete mode 100644 src/Avalonia.Base/Data/Core/ExpressionObserver.cs
 create mode 100644 src/Avalonia.Base/Data/Core/IBinding2.cs
 create mode 100644 src/Avalonia.Base/Data/Core/IBindingExpressionSink.cs
 delete mode 100644 src/Avalonia.Base/Data/Core/ITransformNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/IndexerBindingExpression.cs
 delete mode 100644 src/Avalonia.Base/Data/Core/IndexerExpressionNode.cs
 delete mode 100644 src/Avalonia.Base/Data/Core/IndexerNodeBase.cs
 delete mode 100644 src/Avalonia.Base/Data/Core/LogicalNotNode.cs
 delete mode 100644 src/Avalonia.Base/Data/Core/MarkupBindingChainException.cs
 create mode 100644 src/Avalonia.Base/Data/Core/Parsers/BindingExpressionVisitor.cs
 delete mode 100644 src/Avalonia.Base/Data/Core/Parsers/ExpressionTreeParser.cs
 delete mode 100644 src/Avalonia.Base/Data/Core/Parsers/ExpressionVisitorNodeBuilder.cs
 create mode 100644 src/Avalonia.Base/Data/Core/Plugins/ObservableStreamPlugin`1.cs
 create mode 100644 src/Avalonia.Base/Data/Core/Plugins/PropertyInfoAccessorPlugin.cs
 create mode 100644 src/Avalonia.Base/Data/Core/Plugins/ReflectionMethodAccessorPlugin.cs
 create mode 100644 src/Avalonia.Base/Data/Core/Plugins/TaskStreamPlugin`1.cs
 delete mode 100644 src/Avalonia.Base/Data/Core/PropertyAccessorNode.cs
 delete mode 100644 src/Avalonia.Base/Data/Core/SettableNode.cs
 delete mode 100644 src/Avalonia.Base/Data/Core/StreamNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/TargetTypeConverter.cs
 delete mode 100644 src/Avalonia.Base/Data/Core/TypeCastNode.cs
 create mode 100644 src/Avalonia.Base/Data/Core/UntypedBindingExpressionBase.cs
 create mode 100644 src/Avalonia.Base/Data/Core/UntypedObservableBindingExpression.cs
 rename src/{Markup/Avalonia.Markup => Avalonia.Base}/Data/CultureInfoIetfLanguageTagConverter.cs (100%)
 create mode 100644 src/Avalonia.Base/Data/TemplateBinding.Observable.cs
 create mode 100644 src/Avalonia.Base/Data/UpdateSourceTrigger.cs
 create mode 100644 src/Avalonia.Base/Diagnostics/ObsoletionMessages.cs
 delete mode 100644 src/Avalonia.Base/PropertyStore/LoggingUtils.cs
 delete mode 100644 src/Avalonia.Base/PropertyStore/UntypedBindingEntry.cs
 delete mode 100644 src/Avalonia.Base/Styling/PropertySetterBindingInstance.cs
 create mode 100644 src/Markup/Avalonia.Markup.Xaml/Data/DynamicResourceExpression.cs
 delete mode 100644 src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/ArrayElementPlugin.cs
 delete mode 100644 src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/CommandAccessorPlugin.cs
 delete mode 100644 src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/FindVisualAncestorNode.cs
 delete mode 100644 src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/MethodAccessorPlugin.cs
 delete mode 100644 src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/ObservableStreamPlugin.cs
 delete mode 100644 src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/PropertyInfoAccessorPlugin.cs
 delete mode 100644 src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/StrongTypeCastNode.cs
 create mode 100644 src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionNodeFactory.cs
 delete mode 100644 src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionObserverBuilder.cs
 delete mode 100644 src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionParser.cs
 delete mode 100644 src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/ElementNameNode.cs
 delete mode 100644 src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/FindAncestorNode.cs
 delete mode 100644 src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/SelfNode.cs
 delete mode 100644 src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/StringIndexerNode.cs
 create mode 100644 tests/Avalonia.Base.UnitTests/Animation/StyleAnimationTests.cs
 create mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.AttachedProperty.cs
 create mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.AvaloniaProperty.cs
 create mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.DataValidation.cs
 create mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.GetValue.cs
 create mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Indexer.cs
 create mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Mode.cs
 create mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Negation.cs
 create mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Observable.cs
 create mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Property.cs
 create mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.SetValue.cs
 create mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Task.cs
 create mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.UpdateSourceTrigger.cs
 create mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/BindingPathFromExpressionBuilder.cs
 create mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/CompiledBindingPathFromExpressionBuilder.cs
 delete mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_AttachedProperty.cs
 delete mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_AvaloniaProperty.cs
 delete mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_DataValidation.cs
 delete mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_ExpressionTree.cs
 delete mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Indexer.cs
 delete mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Lifetime.cs
 delete mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Negation.cs
 delete mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Observable.cs
 delete mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Property.cs
 delete mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_SetValue.cs
 delete mode 100644 tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Task.cs
 create mode 100644 tests/Avalonia.Benchmarks/Data/Binding_Setup.cs
 create mode 100644 tests/Avalonia.Benchmarks/Data/Binding_Values.cs
 delete mode 100644 tests/Avalonia.Benchmarks/Data/BindingsBenchmark.cs
 create mode 100644 tests/Avalonia.Benchmarks/Data/TemplateBinding_Setup.cs
 create mode 100644 tests/Avalonia.Benchmarks/Data/TemplateBinding_Values.cs
 rename tests/Avalonia.LeakTests/{ExpressionObserverTests.cs => BindingExpressionTests.cs} (74%)
 create mode 100644 tests/Avalonia.Markup.UnitTests/Data/BindingTests_Logging.cs
 rename tests/Avalonia.Markup.UnitTests/Parsers/{ExpressionNodeBuilderTests_Errors.cs => BindingExpressionGrammarTests_Errors.cs} (71%)
 rename tests/Avalonia.Markup.UnitTests/Parsers/{ExpressionNodeBuilderTests.cs => ExpressionPathParsing.cs} (56%)

diff --git a/.ncrunch/Avalonia.Tizen.v3.ncrunchproject b/.ncrunch/Avalonia.Tizen.v3.ncrunchproject
new file mode 100644
index 000000000..319cd523c
--- /dev/null
+++ b/.ncrunch/Avalonia.Tizen.v3.ncrunchproject
@@ -0,0 +1,5 @@
+<ProjectConfiguration>
+  <Settings>
+    <IgnoreThisComponentCompletely>True</IgnoreThisComponentCompletely>
+  </Settings>
+</ProjectConfiguration>
\ No newline at end of file
diff --git a/.ncrunch/ControlCatalog.Tizen.v3.ncrunchproject b/.ncrunch/ControlCatalog.Tizen.v3.ncrunchproject
new file mode 100644
index 000000000..319cd523c
--- /dev/null
+++ b/.ncrunch/ControlCatalog.Tizen.v3.ncrunchproject
@@ -0,0 +1,5 @@
+<ProjectConfiguration>
+  <Settings>
+    <IgnoreThisComponentCompletely>True</IgnoreThisComponentCompletely>
+  </Settings>
+</ProjectConfiguration>
\ No newline at end of file
diff --git a/.ncrunch/ControlCatalog.v3.ncrunchproject b/.ncrunch/ControlCatalog.v3.ncrunchproject
new file mode 100644
index 000000000..319cd523c
--- /dev/null
+++ b/.ncrunch/ControlCatalog.v3.ncrunchproject
@@ -0,0 +1,5 @@
+<ProjectConfiguration>
+  <Settings>
+    <IgnoreThisComponentCompletely>True</IgnoreThisComponentCompletely>
+  </Settings>
+</ProjectConfiguration>
\ No newline at end of file
diff --git a/.ncrunch/PInvoke.net6.0.v3.ncrunchproject b/.ncrunch/PInvoke.net6.0.v3.ncrunchproject
new file mode 100644
index 000000000..319cd523c
--- /dev/null
+++ b/.ncrunch/PInvoke.net6.0.v3.ncrunchproject
@@ -0,0 +1,5 @@
+<ProjectConfiguration>
+  <Settings>
+    <IgnoreThisComponentCompletely>True</IgnoreThisComponentCompletely>
+  </Settings>
+</ProjectConfiguration>
\ No newline at end of file
diff --git a/.ncrunch/PInvoke.netstandard2.0.v3.ncrunchproject b/.ncrunch/PInvoke.netstandard2.0.v3.ncrunchproject
new file mode 100644
index 000000000..319cd523c
--- /dev/null
+++ b/.ncrunch/PInvoke.netstandard2.0.v3.ncrunchproject
@@ -0,0 +1,5 @@
+<ProjectConfiguration>
+  <Settings>
+    <IgnoreThisComponentCompletely>True</IgnoreThisComponentCompletely>
+  </Settings>
+</ProjectConfiguration>
\ No newline at end of file
diff --git a/samples/BindingDemo/MainWindow.xaml b/samples/BindingDemo/MainWindow.xaml
index d1c65ca73..a00bed37f 100644
--- a/samples/BindingDemo/MainWindow.xaml
+++ b/samples/BindingDemo/MainWindow.xaml
@@ -23,6 +23,7 @@
           <StackPanel Margin="18" Spacing="4" Width="200">
             <TextBlock FontSize="16" Text="Simple Bindings"/>
             <TextBox Watermark="Two Way" UseFloatingWatermark="True" Text="{Binding Path=StringValue}" Name="first"/>
+            <TextBox Watermark="Two Way (LostFocus)" UseFloatingWatermark="True" Text="{Binding Path=StringValue, UpdateSourceTrigger=LostFocus}"/>
             <TextBox Watermark="One Way" UseFloatingWatermark="True" Text="{Binding Path=StringValue, Mode=OneWay}"/>
             <TextBox Watermark="One Time" UseFloatingWatermark="True" Text="{Binding Path=StringValue, Mode=OneTime}"/>
             <!-- Removed due to #2983: reinstate when that's fixed.
diff --git a/src/Avalonia.Base/Animation/AnimatorKeyFrame.cs b/src/Avalonia.Base/Animation/AnimatorKeyFrame.cs
index bba512de5..190524402 100644
--- a/src/Avalonia.Base/Animation/AnimatorKeyFrame.cs
+++ b/src/Avalonia.Base/Animation/AnimatorKeyFrame.cs
@@ -47,11 +47,11 @@ namespace Avalonia.Animation
 
             if (value is IBinding binding)
             {
-                return this.Bind(ValueProperty, binding, targetControl);
+                return Bind(ValueProperty, binding, targetControl);
             }
             else
             {
-                return this.Bind(ValueProperty, Observable.SingleValue(value).ToBinding(), targetControl);
+                return Bind(ValueProperty, Observable.SingleValue(value).ToBinding(), targetControl);
             }
         }
 
diff --git a/src/Avalonia.Base/AvaloniaObject.cs b/src/Avalonia.Base/AvaloniaObject.cs
index f3a046ef8..9bebec802 100644
--- a/src/Avalonia.Base/AvaloniaObject.cs
+++ b/src/Avalonia.Base/AvaloniaObject.cs
@@ -3,9 +3,11 @@ using System.Collections.Generic;
 using System.ComponentModel;
 using System.Runtime.CompilerServices;
 using Avalonia.Data;
+using Avalonia.Data.Core;
 using Avalonia.Diagnostics;
 using Avalonia.Logging;
 using Avalonia.PropertyStore;
+using Avalonia.Reactive;
 using Avalonia.Threading;
 
 namespace Avalonia
@@ -406,6 +408,19 @@ namespace Avalonia
             }
         }
 
+        /// <summary>
+        /// Binds a <see cref="AvaloniaProperty"/> to an <see cref="IBinding"/>.
+        /// </summary>
+        /// <param name="property">The property.</param>
+        /// <param name="binding">The binding.</param>
+        /// <returns>
+        /// The binding expression which represents the binding instance on this object.
+        /// </returns>
+        public BindingExpressionBase Bind(AvaloniaProperty property, IBinding binding)
+        {
+            return Bind(property, binding, null);
+        }
+
         /// <summary>
         /// Binds a <see cref="AvaloniaProperty"/> to an observable.
         /// </summary>
@@ -440,7 +455,21 @@ namespace Avalonia
             VerifyAccess();
             ValidatePriority(priority);
 
-            return _values.AddBinding(property, source, priority);
+            if (source is IBinding2 b)
+            {
+                if (b.Instance(this, property, null) is not UntypedBindingExpressionBase expression)
+                    throw new NotSupportedException("Binding returned unsupported IBindingExpression.");
+                if (priority != expression.Priority)
+                    throw new NotSupportedException(
+                        $"The binding priority passed to AvaloniaObject.Bind ('{priority}') " +
+                        "conflicts with the binding priority of the provided binding expression " +
+                        $" ({expression.Priority}').");
+                return GetValueStore().AddBinding(property, expression);
+            }
+            else
+            {
+                return _values.AddBinding(property, source, priority);
+            }
         }
 
         /// <summary>
@@ -512,7 +541,16 @@ namespace Avalonia
                 throw new ArgumentException($"The property {property.Name} is readonly.");
             }
 
-            return _values.AddBinding(property, source);
+            if (source is IBinding2 b)
+            {
+                if (b.Instance(this, property, null) is not UntypedBindingExpressionBase expression)
+                    throw new NotSupportedException("Binding returned unsupported IBindingExpression.");
+                return GetValueStore().AddBinding(property, expression);
+            }
+            else
+            {
+                return _values.AddBinding(property, source);
+            }
         }
 
         /// <summary>
@@ -573,6 +611,30 @@ namespace Avalonia
         /// <param name="property">The property.</param>
         public void CoerceValue(AvaloniaProperty property) => _values.CoerceValue(property);
 
+        /// <summary>
+        /// Binds a <see cref="AvaloniaProperty"/> to an <see cref="IBinding"/>.
+        /// </summary>
+        /// <param name="property">The property.</param>
+        /// <param name="binding">The binding.</param>
+        /// <param name="anchor">
+        /// An optional anchor from which to locate required context. When binding to objects that
+        /// are not in the logical tree, certain types of binding need an anchor into the tree in 
+        /// order to locate named controls or resources. The <paramref name="anchor"/> parameter 
+        /// can be used to provide this context.
+        /// </param>
+        /// <returns>
+        /// The binding expression which represents the binding instance on this object.
+        /// </returns>
+        internal BindingExpressionBase Bind(AvaloniaProperty property, IBinding binding, object? anchor)
+        {
+            if (binding is not IBinding2 b)
+                throw new NotSupportedException($"Unsupported IBinding implementation '{binding}'.");
+            if (b.Instance(this, property, anchor) is not UntypedBindingExpressionBase expression)
+                throw new NotSupportedException("Binding returned unsupported IBindingExpression.");
+
+            return GetValueStore().AddBinding(property, expression);
+        }
+
         internal void AddInheritanceChild(AvaloniaObject child)
         {
             _inheritanceChildren ??= new List<AvaloniaObject>();
@@ -608,22 +670,6 @@ namespace Avalonia
         internal ValueStore GetValueStore() => _values;
         internal IReadOnlyList<AvaloniaObject>? GetInheritanceChildren() => _inheritanceChildren;
 
-        /// <summary>
-        /// Gets a logger to which a binding warning may be written.
-        /// </summary>
-        /// <param name="property">The property that the error occurred on.</param>
-        /// <param name="e">The binding exception, if any.</param>
-        /// <remarks>
-        /// This is overridden in <see cref="Visual"/> to prevent logging binding errors when a
-        /// control is not attached to the visual tree.
-        /// </remarks>
-        internal virtual ParametrizedLogger? GetBindingWarningLogger(
-            AvaloniaProperty property,
-            Exception? e)
-        {
-            return Logger.TryGet(LogEventLevel.Warning, LogArea.Binding);
-        }
-
         /// <summary>
         /// Called to update the validation state for properties for which data validation is
         /// enabled.
@@ -757,8 +803,6 @@ namespace Avalonia
         /// <param name="value">The value.</param>
         internal void SetDirectValueUnchecked<T>(DirectPropertyBase<T> property, BindingValue<T> value)
         {
-            LoggingUtils.LogIfNecessary(this, property, value);
-
             switch (value.Type)
             {
                 case BindingValueType.UnsetValue:
diff --git a/src/Avalonia.Base/AvaloniaObjectExtensions.cs b/src/Avalonia.Base/AvaloniaObjectExtensions.cs
index 7becd1c99..90465057b 100644
--- a/src/Avalonia.Base/AvaloniaObjectExtensions.cs
+++ b/src/Avalonia.Base/AvaloniaObjectExtensions.cs
@@ -1,5 +1,6 @@
 using System;
 using Avalonia.Data;
+using Avalonia.Data.Core;
 using Avalonia.Reactive;
 
 namespace Avalonia
@@ -233,9 +234,10 @@ namespace Avalonia
         /// An optional anchor from which to locate required context. When binding to objects that
         /// are not in the logical tree, certain types of binding need an anchor into the tree in 
         /// order to locate named controls or resources. The <paramref name="anchor"/> parameter 
-        /// can be used to provice this context.
+        /// can be used to provide this context.
         /// </param>
         /// <returns>An <see cref="IDisposable"/> which can be used to cancel the binding.</returns>
+        [Obsolete("Use AvaloniaObject.Bind(AvaloniaProperty, IBinding")]
         public static IDisposable Bind(
             this AvaloniaObject target,
             AvaloniaProperty property,
@@ -246,20 +248,7 @@ namespace Avalonia
             property = property ?? throw new ArgumentNullException(nameof(property));
             binding = binding ?? throw new ArgumentNullException(nameof(binding));
 
-            var result = binding.Initiate(
-                target,
-                property,
-                anchor,
-                property.GetMetadata(target.GetType()).EnableDataValidation ?? false);
-
-            if (result != null)
-            {
-                return BindingOperations.Apply(target, property, result, anchor);
-            }
-            else
-            {
-                return Disposable.Empty;
-            }
+            return target.Bind(property, binding);
         }
 
         /// <summary>
@@ -367,7 +356,7 @@ namespace Avalonia
             return observable.Subscribe(new ClassHandlerObserver<TTarget, TValue>(action));
         }
 
-        private class BindingAdaptor : IBinding
+        private class BindingAdaptor : IBinding2
         {
             private readonly IObservable<object?> _source;
 
@@ -382,7 +371,13 @@ namespace Avalonia
                 object? anchor = null,
                 bool enableDataValidation = false)
             {
-                return InstancedBinding.OneWay(_source);
+                var expression = new UntypedObservableBindingExpression(_source, BindingPriority.LocalValue);
+                return new InstancedBinding(expression, BindingMode.OneWay, BindingPriority.LocalValue);
+            }
+
+            BindingExpressionBase IBinding2.Instance(AvaloniaObject target, AvaloniaProperty property, object? anchor)
+            {
+                return new UntypedObservableBindingExpression(_source, BindingPriority.LocalValue);
             }
         }
 
diff --git a/src/Avalonia.Base/AvaloniaProperty.cs b/src/Avalonia.Base/AvaloniaProperty.cs
index 5ab52cfde..a56f3f098 100644
--- a/src/Avalonia.Base/AvaloniaProperty.cs
+++ b/src/Avalonia.Base/AvaloniaProperty.cs
@@ -542,6 +542,14 @@ namespace Avalonia
         /// <param name="value">The value.</param>
         internal abstract void RouteSetCurrentValue(AvaloniaObject o, object? value);
 
+        /// <summary>
+        /// Routes an untyped SetDirectValueUnchecked call to a typed call.
+        /// </summary>
+        /// <param name="o">The object instance.</param>
+        /// <param name="value">The value.</param>
+        internal virtual void RouteSetDirectValueUnchecked(AvaloniaObject o, object? value) =>
+            throw new NotSupportedException();
+
         /// <summary>
         /// Routes an untyped Bind call to a typed call.
         /// </summary>
diff --git a/src/Avalonia.Base/ClassBindingManager.cs b/src/Avalonia.Base/ClassBindingManager.cs
index 55f3a7892..ecb586304 100644
--- a/src/Avalonia.Base/ClassBindingManager.cs
+++ b/src/Avalonia.Base/ClassBindingManager.cs
@@ -14,7 +14,7 @@ namespace Avalonia
         {
             if (!s_RegisteredProperties.TryGetValue(className, out var prop))
                 s_RegisteredProperties[className] = prop = RegisterClassProxyProperty(className);
-            return target.Bind(prop, source, anchor);
+            return target.Bind(prop, source);
         }
 
         [System.Diagnostics.CodeAnalysis.SuppressMessage("AvaloniaProperty", "AVP1001:The same AvaloniaProperty should not be registered twice",
diff --git a/src/Avalonia.Base/Data/BindingChainException.cs b/src/Avalonia.Base/Data/BindingChainException.cs
index 189decf9d..517440eb9 100644
--- a/src/Avalonia.Base/Data/BindingChainException.cs
+++ b/src/Avalonia.Base/Data/BindingChainException.cs
@@ -4,8 +4,8 @@ namespace Avalonia.Data
 {
     /// <summary>
     /// An exception returned through <see cref="BindingNotification"/> signaling that a
-    /// requested binding expression could not be evaluated because of a null in one of the links
-    /// of the binding chain.
+    /// requested binding expression could not be evaluated because of an error in one of
+    /// the links of the binding chain.
     /// </summary>
     public class BindingChainException : Exception
     {
@@ -60,15 +60,15 @@ namespace Avalonia.Data
             {
                 if (Expression != null && ExpressionErrorPoint != null)
                 {
-                    return $"{_message} in expression '{Expression}' at '{ExpressionErrorPoint}'.";
+                    return $"An error occured binding to '{Expression}' at '{ExpressionErrorPoint}': '{_message}'";
                 }
-                else if (ExpressionErrorPoint != null)
+                else if (Expression != null)
                 {
-                    return $"{_message} in expression '{ExpressionErrorPoint}'.";
+                    return $"An error occured binding to '{Expression}': '{_message}'";
                 }
                 else
                 {
-                    return $"{_message} in expression.";
+                    return $"An error occured in a binding: '{_message}'";
                 }
             }
         }
diff --git a/src/Avalonia.Base/Data/BindingExpressionBase.cs b/src/Avalonia.Base/Data/BindingExpressionBase.cs
new file mode 100644
index 000000000..616f64d9d
--- /dev/null
+++ b/src/Avalonia.Base/Data/BindingExpressionBase.cs
@@ -0,0 +1,55 @@
+using System;
+using Avalonia.PropertyStore;
+using Avalonia.Styling;
+
+namespace Avalonia.Data;
+
+public abstract class BindingExpressionBase : IDisposable, ISetterInstance
+{
+    private protected BindingExpressionBase()
+    {
+    }
+
+    internal BindingMode Mode { get; private protected set; }
+
+    public virtual void Dispose()
+    {
+        GC.SuppressFinalize(this);
+    }
+
+    /// <summary>
+    /// Sends the current binding target value to the binding source property in 
+    /// <see cref="BindingMode.TwoWay"/> or <see cref="BindingMode.OneWayToSource"/> bindings.
+    /// </summary>
+    /// <remarks>
+    /// This method does nothing when the Mode of the binding is not 
+    /// <see cref="BindingMode.TwoWay"/> or <see cref="BindingMode.OneWayToSource"/>.
+    /// 
+    /// If the UpdateSourceTrigger value of your binding is set to
+    /// <see cref="UpdateSourceTrigger.Explicit"/>, you must call the 
+    /// <see cref="UpdateSource"/> method or the changes will not propagate back to the
+    /// source.
+    /// </remarks>
+    public virtual void UpdateSource() { }
+
+    /// <summary>
+    /// Forces a data transfer from the binding source to the binding target.
+    /// </summary>
+    public virtual void UpdateTarget() { }
+
+    /// <summary>
+    /// When overridden in a derived class, attaches the binding expression to a value store but
+    /// does not start it.
+    /// </summary>
+    /// <param name="valueStore">The value store to attach to.</param>
+    /// <param name="frame">The immediate value frame to attach to, if any.</param>
+    /// <param name="target">The target object.</param>
+    /// <param name="targetProperty">The target property.</param>
+    /// <param name="priority">The priority of the binding.</param>
+    internal abstract void Attach(
+        ValueStore valueStore,
+        ImmediateValueFrame? frame,
+        AvaloniaObject target,
+        AvaloniaProperty targetProperty,
+        BindingPriority priority);
+}
diff --git a/src/Avalonia.Base/Data/BindingNotification.cs b/src/Avalonia.Base/Data/BindingNotification.cs
index b67056e55..0c940a146 100644
--- a/src/Avalonia.Base/Data/BindingNotification.cs
+++ b/src/Avalonia.Base/Data/BindingNotification.cs
@@ -1,4 +1,6 @@
 using System;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
 
 namespace Avalonia.Data
 {
@@ -55,6 +57,7 @@ namespace Avalonia.Data
         /// <param name="value">The binding value.</param>
         public BindingNotification(object? value)
         {
+            Debug.Assert(value is not BindingNotification);
             _value = value;
         }
 
@@ -162,6 +165,31 @@ namespace Avalonia.Data
             return notification is not null ? notification.Value : o;
         }
 
+        /// <summary>
+        /// Updates the value of an object that may be a <see cref="BindingNotification"/>.
+        /// </summary>
+        /// <param name="o">The object that may be a binding notification.</param>
+        /// <param name="value">The new value.</param>
+        /// <returns>
+        /// The updated binding notification if <paramref name="o"/> is a binding notification;
+        /// otherwise <paramref name="value"/>.
+        /// </returns>
+        /// <remarks>
+        /// If <paramref name="o"/> is a <see cref="BindingNotification"/> then sets its value
+        /// to <paramref name="value"/>. If <paramref name="value"/> is a
+        /// <see cref="BindingNotification"/> then the value will first be extracted.
+        /// </remarks>
+        public static object? UpdateValue(object o, object value)
+        {
+            if (o is BindingNotification n)
+            {
+                n.SetValue(ExtractValue(value));
+                return n;
+            }
+
+            return value;
+        }
+
         /// <summary>
         /// Gets an exception from an object that may be a <see cref="BindingNotification"/>.
         /// </summary>
@@ -261,4 +289,17 @@ namespace Avalonia.Data
                    a?.Message == b?.Message;
         }
     }
+
+    internal static class BindingErrorTypeExtensions
+    {
+        public static BindingValueType ToBindingValueType(this BindingErrorType type)
+        {
+            return type switch
+            {
+                BindingErrorType.Error => BindingValueType.BindingError,
+                BindingErrorType.DataValidationError => BindingValueType.DataValidationError,
+                _ => BindingValueType.Value,
+            };
+        }
+    }
 }
diff --git a/src/Avalonia.Base/Data/BindingOperations.cs b/src/Avalonia.Base/Data/BindingOperations.cs
index e53ae40cb..23a3f532a 100644
--- a/src/Avalonia.Base/Data/BindingOperations.cs
+++ b/src/Avalonia.Base/Data/BindingOperations.cs
@@ -1,4 +1,5 @@
 using System;
+using Avalonia.Diagnostics;
 using Avalonia.Reactive;
 
 namespace Avalonia.Data
@@ -13,23 +14,22 @@ namespace Avalonia.Data
         /// <param name="target">The target object.</param>
         /// <param name="property">The property to bind.</param>
         /// <param name="binding">The instanced binding.</param>
-        /// <param name="anchor">
-        /// An optional anchor from which to locate required context. When binding to objects that
-        /// are not in the logical tree, certain types of binding need an anchor into the tree in 
-        /// order to locate named controls or resources. The <paramref name="anchor"/> parameter 
-        /// can be used to provide this context.
-        /// </param>
         /// <returns>An <see cref="IDisposable"/> which can be used to cancel the binding.</returns>
+        [Obsolete(ObsoletionMessages.MayBeRemovedInAvalonia12)]
         public static IDisposable Apply(
             AvaloniaObject target,
             AvaloniaProperty property,
-            InstancedBinding binding,
-            object? anchor)
+            InstancedBinding binding)
         {
             _ = target ?? throw new ArgumentNullException(nameof(target));
             _ = property ?? throw new ArgumentNullException(nameof(property));
             _ = binding ?? throw new ArgumentNullException(nameof(binding));
 
+            if (binding.Expression is { } expression)
+            {
+                return target.GetValueStore().AddBinding(property, expression);
+            }
+
             var mode = binding.Mode;
 
             if (mode == BindingMode.Default)
@@ -83,6 +83,24 @@ namespace Avalonia.Data
             }
         }
 
+        /// <summary>
+        /// Applies an <see cref="InstancedBinding"/> a property on an <see cref="AvaloniaObject"/>.
+        /// </summary>
+        /// <param name="target">The target object.</param>
+        /// <param name="property">The property to bind.</param>
+        /// <param name="binding">The instanced binding.</param>
+        /// <param name="anchor">Obsolete, unused.</param>
+        /// <returns>An <see cref="IDisposable"/> which can be used to cancel the binding.</returns>
+        [Obsolete("Use the Apply(AvaloniaObject, AvaloniaProperty, InstancedBinding) overload.")]
+        public static IDisposable Apply(
+            AvaloniaObject target,
+            AvaloniaProperty property,
+            InstancedBinding binding,
+            object? anchor)
+        {
+            return Apply(target, property, binding);
+        }
+
         private sealed class TwoWayBindingDisposable : IDisposable
         {
             private readonly IDisposable _toTargetSubscription;
diff --git a/src/Avalonia.Base/Data/BindingValue.cs b/src/Avalonia.Base/Data/BindingValue.cs
index ac79d1eff..6d2872fc8 100644
--- a/src/Avalonia.Base/Data/BindingValue.cs
+++ b/src/Avalonia.Base/Data/BindingValue.cs
@@ -415,6 +415,45 @@ namespace Avalonia.Data
                 e);
         }
 
+        /// <summary>
+        /// Creates a <see cref="BindingValue{T}"/> from an object, handling the special values
+        /// <see cref="AvaloniaProperty.UnsetValue"/>, <see cref="BindingOperations.DoNothing"/> and
+        /// <see cref="BindingNotification"/> without type conversion.
+        /// </summary>
+        /// <param name="value">The untyped value.</param>
+        /// <returns>The typed binding value.</returns>
+        internal static BindingValue<T> FromUntypedStrict(object? value)
+        {
+            if (value == AvaloniaProperty.UnsetValue)
+                return Unset;
+            else if (value == BindingOperations.DoNothing)
+                return DoNothing;
+
+            var type = BindingValueType.Value;
+            T? v = default;
+            Exception? error = null;
+
+            if (value is BindingNotification n)
+            {
+                error = n.Error;
+                type = n.ErrorType switch
+                {
+                    BindingErrorType.Error => BindingValueType.BindingError,
+                    BindingErrorType.DataValidationError => BindingValueType.DataValidationError,
+                    _ => BindingValueType.Value,
+                };
+
+                if (n.HasValue)
+                    type |= BindingValueType.HasValue;
+                value = n.Value;
+            }
+
+            if ((type & BindingValueType.HasValue) != 0)
+                v = (T)value!;
+
+            return new BindingValue<T>(type, v, error);
+        }
+
         [Conditional("DEBUG")]
         private static void ValidateValue(T value)
         {
diff --git a/src/Avalonia.Base/Data/Core/AvaloniaPropertyAccessorNode.cs b/src/Avalonia.Base/Data/Core/AvaloniaPropertyAccessorNode.cs
deleted file mode 100644
index 4bf24e901..000000000
--- a/src/Avalonia.Base/Data/Core/AvaloniaPropertyAccessorNode.cs
+++ /dev/null
@@ -1,57 +0,0 @@
-using System;
-using Avalonia.Reactive;
-
-namespace Avalonia.Data.Core
-{
-    internal class AvaloniaPropertyAccessorNode : SettableNode
-    {
-        private IDisposable? _subscription;
-        private readonly bool _enableValidation;
-        private readonly AvaloniaProperty _property;
-
-        public AvaloniaPropertyAccessorNode(AvaloniaProperty property, bool enableValidation)
-        {
-            _property = property;
-            _enableValidation = enableValidation;
-        }
-
-        public override string? Description => PropertyName;
-        public string? PropertyName { get; }
-        public override Type PropertyType => _property.PropertyType;
-
-        protected override bool SetTargetValueCore(object? value, BindingPriority priority)
-        {
-            try
-            {
-                if (Target.TryGetTarget(out var target) && target is AvaloniaObject obj)
-                {
-                    obj.SetValue(_property, value, priority);
-                    return true;
-                }
-                return false;
-            }
-            catch
-            {
-                return false;
-            }
-        }
-
-        protected override void StartListeningCore(WeakReference<object?> reference)
-        {
-            if (reference.TryGetTarget(out var target) && target is AvaloniaObject obj)
-            {
-                _subscription = new AvaloniaPropertyObservable<object?,object?>(obj, _property).Subscribe(ValueChanged);
-            }
-            else
-            {
-                _subscription = null;
-            }
-        }
-
-        protected override void StopListeningCore()
-        {
-            _subscription?.Dispose();
-            _subscription = null;
-        }
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/BindingError.cs b/src/Avalonia.Base/Data/Core/BindingError.cs
new file mode 100644
index 000000000..b1cc9b9ca
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/BindingError.cs
@@ -0,0 +1,18 @@
+using System;
+using System.Diagnostics;
+
+namespace Avalonia.Data.Core;
+
+internal class BindingError
+{
+    public BindingError(Exception exception, BindingErrorType errorType)
+    {
+        Debug.Assert(errorType != BindingErrorType.None);
+
+        Exception = exception;
+        ErrorType = errorType;
+    }
+
+    public Exception Exception { get; }
+    public BindingErrorType ErrorType { get; }
+}
diff --git a/src/Avalonia.Base/Data/Core/BindingExpression.cs b/src/Avalonia.Base/Data/Core/BindingExpression.cs
index 7c6846484..20cca96b3 100644
--- a/src/Avalonia.Base/Data/Core/BindingExpression.cs
+++ b/src/Avalonia.Base/Data/Core/BindingExpression.cs
@@ -1,389 +1,565 @@
-using System;
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
-using Avalonia.Reactive;
+using System.Linq.Expressions;
+using System.Text;
 using Avalonia.Data.Converters;
+using Avalonia.Data.Core.ExpressionNodes;
+using Avalonia.Data.Core.Parsers;
+using Avalonia.Input;
+using Avalonia.Interactivity;
 using Avalonia.Logging;
 using Avalonia.Utilities;
 
-namespace Avalonia.Data.Core
+namespace Avalonia.Data.Core;
+
+/// <summary>
+/// A binding expression which accepts and produces (possibly boxed) object values.
+/// </summary>
+/// <remarks>
+/// A <see cref="BindingExpression"/> represents a untyped binding which has been
+/// instantiated on an object.
+/// </remarks>
+internal partial class BindingExpression : UntypedBindingExpressionBase, IDescription, IDisposable
 {
+    private static readonly List<ExpressionNode> s_emptyExpressionNodes = new();
+    private readonly WeakReference<object?>? _source;
+    private readonly BindingMode _mode;
+    private readonly List<ExpressionNode> _nodes;
+    private readonly TargetTypeConverter? _targetTypeConverter;
+    private readonly UncommonFields? _uncommon;
+
     /// <summary>
-    /// Binds to an expression on an object using a type value converter to convert the values
-    /// that are sent and received.
+    /// Initializes a new instance of the <see cref="BindingExpression"/> class.
     /// </summary>
-    [RequiresUnreferencedCode(TrimmingMessages.TypeConversionRequiresUnreferencedCodeMessage)]
-    internal class BindingExpression : LightweightObservableBase<object?>, IAvaloniaSubject<object?>, IDescription
+    /// <param name="source">The source from which the value will be read.</param>
+    /// <param name="nodes">The nodes representing the binding path.</param>
+    /// <param name="fallbackValue">
+    /// The fallback value. Pass <see cref="AvaloniaProperty.UnsetValue"/> for no fallback.
+    /// </param>
+    /// <param name="converter">The converter to use.</param>
+    /// <param name="converterCulture">The converter culture to use.</param>
+    /// <param name="converterParameter">The converter parameter.</param>
+    /// <param name="enableDataValidation">
+    /// Whether data validation should be enabled for the binding.
+    /// </param>
+    /// <param name="mode">The binding mode.</param>
+    /// <param name="priority">The binding priority.</param>
+    /// <param name="stringFormat">The format string to use.</param>
+    /// <param name="targetNullValue">The null target value.</param>
+    /// <param name="targetTypeConverter">
+    /// A final type converter to be run on the produced value.
+    /// </param>
+    /// <param name="updateSourceTrigger">The trigger for updating the source value.</param>
+    public BindingExpression(
+        object? source,
+        List<ExpressionNode>? nodes,
+        object? fallbackValue,
+        IValueConverter? converter = null,
+        CultureInfo? converterCulture = null,
+        object? converterParameter = null,
+        bool enableDataValidation = false,
+        BindingMode mode = BindingMode.OneWay,
+        BindingPriority priority = BindingPriority.LocalValue,
+        string? stringFormat = null,
+        object? targetNullValue = null,
+        TargetTypeConverter? targetTypeConverter = null,
+        UpdateSourceTrigger updateSourceTrigger = UpdateSourceTrigger.PropertyChanged)
+            : base(priority, enableDataValidation)
     {
-        private readonly ExpressionObserver _inner;
-        private readonly Type _targetType;
-        private readonly object? _fallbackValue;
-        private readonly object? _targetNullValue;
-        private readonly BindingPriority _priority;
-        InnerListener? _innerListener;
-        WeakReference<object>? _value;
+        if (mode == BindingMode.Default)
+            throw new ArgumentException("Binding mode cannot be Default.", nameof(mode));
+        if (updateSourceTrigger == UpdateSourceTrigger.Default)
+            throw new ArgumentException("UpdateSourceTrigger cannot be Default.", nameof(updateSourceTrigger));
 
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ExpressionObserver"/> class.
-        /// </summary>
-        /// <param name="inner">The <see cref="ExpressionObserver"/>.</param>
-        /// <param name="targetType">The type to convert the value to.</param>
-        public BindingExpression(ExpressionObserver inner, Type targetType)
-            : this(inner, targetType, DefaultValueConverter.Instance, CultureInfo.InvariantCulture)
+        if (source == AvaloniaProperty.UnsetValue)
+            source = null;
+
+        _source = new(source);
+        _mode = mode;
+        _nodes = nodes ?? s_emptyExpressionNodes;
+        _targetTypeConverter = targetTypeConverter;
+
+        if (converter is not null ||
+            converterCulture is not null ||
+            converterParameter is not null ||
+            fallbackValue != AvaloniaProperty.UnsetValue ||
+            !string.IsNullOrWhiteSpace(stringFormat) ||
+            (targetNullValue is not null && targetNullValue != AvaloniaProperty.UnsetValue) ||
+            updateSourceTrigger is not UpdateSourceTrigger.PropertyChanged)
         {
-        }
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ExpressionObserver"/> class.
-        /// </summary>
-        /// <param name="inner">The <see cref="ExpressionObserver"/>.</param>
-        /// <param name="targetType">The type to convert the value to.</param>
-        /// <param name="converter">The value converter to use.</param>
-        /// <param name="converterCulture">The converter culture to use.</param>
-        /// <param name="converterParameter">
-        /// A parameter to pass to <paramref name="converter"/>.
-        /// </param>
-        /// <param name="priority">The binding priority.</param>
-        public BindingExpression(
-            ExpressionObserver inner,
-            Type targetType,
-            IValueConverter converter,
-            CultureInfo converterCulture,
-            object? converterParameter = null,
-            BindingPriority priority = BindingPriority.LocalValue)
-            : this(
-                inner,
-                targetType,
-                AvaloniaProperty.UnsetValue,
-                AvaloniaProperty.UnsetValue,
-                converter,
-                converterCulture,
-                converterParameter, priority)
-        {
-        }
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ExpressionObserver"/> class.
-        /// </summary>
-        /// <param name="inner">The <see cref="ExpressionObserver"/>.</param>
-        /// <param name="targetType">The type to convert the value to.</param>
-        /// <param name="fallbackValue">
-        /// The value to use when the binding is unable to produce a value.
-        /// </param>
-        /// <param name="targetNullValue">
-        /// The value to use when the binding result is null.
-        /// </param>
-        /// <param name="converter">The value converter to use.</param>
-        /// <param name="converterCulture">The converter culture to use.</param>
-        /// <param name="converterParameter">
-        /// A parameter to pass to <paramref name="converter"/>.
-        /// </param>
-        /// <param name="priority">The binding priority.</param>
-        public BindingExpression(
-            ExpressionObserver inner, 
-            Type targetType,
-            object? fallbackValue,
-            object? targetNullValue,
-            IValueConverter converter,
-            CultureInfo converterCulture,
-            object? converterParameter = null,
-            BindingPriority priority = BindingPriority.LocalValue)
-        {
-            _ = inner ?? throw new ArgumentNullException(nameof(inner));
-            _ = targetType ?? throw new ArgumentNullException(nameof(targetType));
-            _ = converter ?? throw new ArgumentNullException(nameof(converter));
-
-            _inner = inner;
-            _targetType = targetType;
-            Converter = converter;
-            ConverterCulture = converterCulture;
-            ConverterParameter = converterParameter;
-            _fallbackValue = fallbackValue;
-            _targetNullValue = targetNullValue;
-            _priority = priority;
-        }
-
-        /// <summary>
-        /// Gets the converter to use on the expression.
-        /// </summary>
-        public IValueConverter Converter { get; }
-
-        /// <summary>
-        /// Gets or sets the culture in which to evaluate the converter.
-        /// </summary>
-        public CultureInfo ConverterCulture { get; set; }
-
-        /// <summary>
-        /// Gets a parameter to pass to <see cref="Converter"/>.
-        /// </summary>
-        public object? ConverterParameter { get; }
-
-        /// <inheritdoc/>
-        string? IDescription.Description => _inner.Expression;
-
-        /// <inheritdoc/>
-        public void OnCompleted()
-        {
-        }
-
-        /// <inheritdoc/>
-        public void OnError(Exception error)
-        {
-        }
-
-        /// <inheritdoc/>
-        public void OnNext(object? value)
-        {
-            if (value == BindingOperations.DoNothing)
+            _uncommon = new()
             {
-                return;
-            }
-
-            using (_inner.Subscribe(_ => { }))
-            {
-                var type = _inner.ResultType;
-
-                if (type != null)
+                _converter = converter,
+                _converterCulture = converterCulture,
+                _converterParameter = converterParameter,
+                _fallbackValue = fallbackValue,
+                _stringFormat = stringFormat switch
                 {
-                    var converted = Converter.ConvertBack(
-                        value,
-                        type,
-                        ConverterParameter,
-                        ConverterCulture);
+                    string s when string.IsNullOrWhiteSpace(s) => null,
+                    string s when !s.Contains('{') => $"{{0:{stringFormat}}}",
+                    _ => stringFormat,
+                },
+                _targetNullValue = targetNullValue ?? AvaloniaProperty.UnsetValue,
+                _updateSourceTrigger = updateSourceTrigger,
+            };
+        }
 
-                    if (converted == BindingOperations.DoNothing)
-                    {
-                        return;
-                    }
+        IPropertyAccessorNode? leafAccessor = null;
 
-                    if (converted == AvaloniaProperty.UnsetValue)
-                    {
-                        converted = TypeUtilities.Default(type);
-                        _inner.SetValue(converted, _priority);
-                    }
-                    else if (converted is BindingNotification notification)
-                    {
-                        if (notification.ErrorType == BindingErrorType.None)
-                        {
-                            throw new AvaloniaInternalException(
-                                "IValueConverter should not return non-errored BindingNotification.");
-                        }
-
-                        PublishNext(notification);
-
-                        if (_fallbackValue != AvaloniaProperty.UnsetValue)
-                        {
-                            if (TypeUtilities.TryConvert(
-                                type,
-                                _fallbackValue,
-                                ConverterCulture,
-                                out converted))
-                            {
-                                _inner.SetValue(converted, _priority);
-                            }
-                            else
-                            {
-                                Logger.TryGet(LogEventLevel.Error, LogArea.Binding)?.Log(
-                                    this,
-                                    "Could not convert FallbackValue {FallbackValue} to {Type}",
-                                    _fallbackValue,
-                                    type);
-                            }
-                        }
-                    }
-                    else
-                    {
-                        _inner.SetValue(converted, _priority);
-                    }
-                }
+        if (nodes is not null)
+        {
+            for (var i = 0; i < nodes.Count; ++i)
+            {
+                var node = nodes[i];
+                node.SetOwner(this, i);
+                if (node is IPropertyAccessorNode n)
+                    leafAccessor = n;
             }
         }
 
-        protected override void Initialize() => _innerListener = new InnerListener(this);
-        protected override void Deinitialize() => _innerListener?.Dispose();
+        if (enableDataValidation)
+            leafAccessor?.EnableDataValidation();
+    }
 
-        protected override void Subscribed(IObserver<object> observer, bool first)
+    public override string Description
+    {
+        get
         {
-            if (!first && _value != null && _value.TryGetTarget(out var val))
-            {
-                observer.OnNext(val);
-            }
-        }
-
-        /// <inheritdoc/>
-        private object? ConvertValue(object? value)
-        {
-            if (value == null && _targetNullValue != AvaloniaProperty.UnsetValue)
-            {
-                return _targetNullValue;
-            }
-
-            if (value == BindingOperations.DoNothing)
-            {
-                return value;
-            }
-
-            var notification = value as BindingNotification;
-
-            if (notification == null)
-            {
-                var converted = Converter.Convert(
-                    value,
-                    _targetType,
-                    ConverterParameter,
-                    ConverterCulture);
-
-                if (converted == BindingOperations.DoNothing)
-                {
-                    return converted;
-                }
-
-                notification = converted as BindingNotification;
-
-                if (notification?.ErrorType == BindingErrorType.None)
-                {
-                    converted = notification.Value;
-                }
-
-                if (_fallbackValue != AvaloniaProperty.UnsetValue &&
-                    (converted == AvaloniaProperty.UnsetValue || converted is BindingNotification))
-                {
-                    var fallback = ConvertFallback();
-                    converted = Merge(converted, fallback);
-                }
-
-                return converted;
-            }
-            else
-            {
-                return ConvertValue(notification);
-            }
-        }
-
-        private BindingNotification ConvertValue(BindingNotification notification)
-        {
-            if (notification.HasValue)
-            {
-                var converted = ConvertValue(notification.Value);
-                notification = Merge(notification, converted);
-            }
-            else if (_fallbackValue != AvaloniaProperty.UnsetValue)
-            {
-                var fallback = ConvertFallback();
-                notification = Merge(notification, fallback);
-            }
-
-            return notification;
-        }
-
-        private BindingNotification ConvertFallback()
-        {
-            object? converted;
-
-            if (_fallbackValue == AvaloniaProperty.UnsetValue)
-            {
-                throw new AvaloniaInternalException("Cannot call ConvertFallback with no fallback value");
-            }
-
-            if (TypeUtilities.TryConvert(
-                _targetType,
-                _fallbackValue,
-                ConverterCulture,
-                out converted))
-            {
-                return new BindingNotification(converted);
-            }
-            else
-            { 
-                return new BindingNotification(
-                    new InvalidCastException(
-                        $"Could not convert FallbackValue '{_fallbackValue}' to '{_targetType}'"),
-                    BindingErrorType.Error);
-            }
-        }
-
-        private static BindingNotification Merge(object a, BindingNotification b)
-        {
-            var an = a as BindingNotification;
-
-            if (an != null)
-            {
-                Merge(an, b);
-                return an;
-            }
-            else
-            {
-                return b;
-            }
-        }
-
-        private static BindingNotification Merge(BindingNotification a, object? b)
-        {
-            var bn = b as BindingNotification;
-
-            if (bn != null)
-            {
-                Merge(a, bn);
-            }
-            else
-            {
-                a.SetValue(b);
-            }
-
-            return a;
-        }
-
-        private static BindingNotification Merge(BindingNotification a, BindingNotification b)
-        {
-            if (b.HasValue)
-            {
-                a.SetValue(b.Value);
-            }
-            else
-            {
-                a.ClearValue();
-            }
-
-            if (b.Error != null)
-            {
-                a.AddError(b.Error, b.ErrorType);
-            }
-
-            return a;
-        }
-
-        public class InnerListener : IObserver<object?>, IDisposable
-        {
-            private readonly BindingExpression _owner;
-            private readonly IDisposable _dispose;
-
-            public InnerListener(BindingExpression owner)
-            {
-                _owner = owner;
-                _dispose = owner._inner.Subscribe(this);
-            }
-
-            public void Dispose() => _dispose.Dispose();
-            public void OnCompleted() => _owner.PublishCompleted();
-            public void OnError(Exception error) => _owner.PublishError(error);
-
-            public void OnNext(object? value)
-            {
-                if (value == BindingOperations.DoNothing)
-                {
-                    return;
-                }
-
-                var converted = _owner.ConvertValue(value);
-
-                if (converted == BindingOperations.DoNothing)
-                {
-                    return;
-                }
-
-                _owner._value = converted is not null ? new WeakReference<object>(converted) : null;
-                _owner.PublishNext(converted);
-            }
+            var b = new StringBuilder();
+            LeafNode.BuildString(b, _nodes);
+            return b.ToString();
         }
     }
+
+    public Type? SourceType => (LeafNode as ISettableNode)?.ValueType;
+    public IValueConverter? Converter => _uncommon?._converter;
+    public CultureInfo ConverterCulture => _uncommon?._converterCulture ?? CultureInfo.CurrentCulture;
+    public object? ConverterParameter => _uncommon?._converterParameter;
+    public object? FallbackValue => _uncommon is not null ? _uncommon._fallbackValue : AvaloniaProperty.UnsetValue;
+    public ExpressionNode LeafNode => _nodes[_nodes.Count - 1];
+    public string? StringFormat => _uncommon?._stringFormat;
+    public object? TargetNullValue => _uncommon?._targetNullValue ?? AvaloniaProperty.UnsetValue;
+    public UpdateSourceTrigger UpdateSourceTrigger => _uncommon?._updateSourceTrigger ?? UpdateSourceTrigger.PropertyChanged;
+
+    public override void UpdateSource()
+    {
+        if (_mode is BindingMode.TwoWay or BindingMode.OneWayToSource)
+            WriteTargetValueToSource();
+    }
+
+    public override void UpdateTarget()
+    {
+        if (_nodes.Count == 0)
+            return;
+
+        var source = _nodes[0].Source;
+
+        for (var i = 0; i < _nodes.Count; ++i)
+            _nodes[i].SetSource(null, null);
+
+        _nodes[0].SetSource(source, null);
+    }
+
+    /// <summary>
+    /// Creates an <see cref="BindingExpression"/> from an expression tree.
+    /// </summary>
+    /// <typeparam name="TIn">The input type of the binding expression.</typeparam>
+    /// <typeparam name="TOut">The output type of the binding expression.</typeparam>
+    /// <param name="source">The source from which the binding value will be read.</param>
+    /// <param name="expression">The expression representing the binding path.</param>
+    /// <param name="converter">The converter to use.</param>
+    /// <param name="converterCulture">The converter culture to use.</param>
+    /// <param name="converterParameter">The converter parameter.</param>
+    /// <param name="enableDataValidation">Whether data validation should be enabled for the binding.</param>
+    /// <param name="fallbackValue">The fallback value.</param>
+    /// <param name="mode">The binding mode.</param>
+    /// <param name="priority">The binding priority.</param>
+    /// <param name="targetNullValue">The null target value.</param>
+    /// <param name="allowReflection">Whether to allow reflection for target type conversion.</param>
+    [RequiresUnreferencedCode(TrimmingMessages.ExpressionNodeRequiresUnreferencedCodeMessage)]
+    internal static BindingExpression Create<TIn, TOut>(
+        TIn source,
+        Expression<Func<TIn, TOut>> expression,
+        IValueConverter? converter = null,
+        CultureInfo? converterCulture = null,
+        object? converterParameter = null,
+        bool enableDataValidation = false,
+        Optional<object?> fallbackValue = default,
+        BindingMode mode = BindingMode.OneWay,
+        BindingPriority priority = BindingPriority.LocalValue,
+        object? targetNullValue = null,
+        bool allowReflection = true)
+            where TIn : class?
+    {
+        var nodes = BindingExpressionVisitor<TIn>.BuildNodes(expression, enableDataValidation);
+        var fallback = fallbackValue.HasValue ? fallbackValue.Value : AvaloniaProperty.UnsetValue;
+
+        return new BindingExpression(
+            source,
+            nodes,
+            fallback,
+            converter: converter,
+            converterCulture: converterCulture,
+            converterParameter: converterParameter,
+            enableDataValidation: enableDataValidation,
+            mode: mode,
+            priority: priority,
+            targetNullValue: targetNullValue,
+            targetTypeConverter: allowReflection ?
+                TargetTypeConverter.GetReflectionConverter() :
+                TargetTypeConverter.GetDefaultConverter());
+    }
+
+    /// <summary>
+    /// Called by an <see cref="ExpressionNode"/> belonging to this binding when its
+    /// <see cref="ExpressionNode.Value"/> changes.
+    /// </summary>
+    /// <param name="nodeIndex">The <see cref="ExpressionNode.Index"/>.</param>
+    /// <param name="value">The <see cref="ExpressionNode.Value"/>.</param>
+    /// <param name="dataValidationError">
+    /// The data validation error associated with the current value, if any.
+    /// </param>
+    internal void OnNodeValueChanged(int nodeIndex, object? value, Exception? dataValidationError)
+    {
+        Debug.Assert(value is not BindingNotification);
+        Debug.Assert(nodeIndex >= 0 && nodeIndex < _nodes.Count);
+
+        if (nodeIndex == _nodes.Count - 1)
+        {
+            // The leaf node has changed. If the binding mode is not OneWayToSource, publish the
+            // value to the target.
+            if (_mode != BindingMode.OneWayToSource)
+            {
+                var error = dataValidationError is not null ?
+                    new BindingError(dataValidationError, BindingErrorType.DataValidationError) :
+                    null;
+                ConvertAndPublishValue(value, error);
+            }
+
+            // If the binding mode is OneTime, then stop the binding if a valid value was published.
+            if (_mode == BindingMode.OneTime && GetValue() != AvaloniaProperty.UnsetValue)
+                Stop();
+        }
+        else if (_mode == BindingMode.OneWayToSource && nodeIndex == _nodes.Count - 2 && value is not null)
+        {
+            // When the binding mode is OneWayToSource, we need to write the value to the source
+            // when the object holding the source property changes; this is node before the leaf
+            // node. First update the leaf node's source, then write the value to its property.
+            _nodes[nodeIndex + 1].SetSource(value, dataValidationError);
+            WriteTargetValueToSource();
+        }
+        else if (value is null)
+        {
+            OnNodeError(nodeIndex, "Value is null.");
+        }
+        else
+        {
+            _nodes[nodeIndex + 1].SetSource(value, dataValidationError);
+        }
+    }
+
+    /// <summary>
+    /// Called by an <see cref="ExpressionNode"/> belonging to this binding when an error occurs
+    /// reading its value.
+    /// </summary>
+    /// <param name="nodeIndex">
+    /// The <see cref="ExpressionNode.Index"/> or -1 if the source is null.
+    /// </param>
+    /// <param name="error">The error message.</param>
+    internal void OnNodeError(int nodeIndex, string error)
+    {
+        // Set the source of all nodes after the one that errored to null. This needs to be done
+        // for each node individually because setting the source to null will not result in
+        // OnNodeValueChanged or OnNodeError being called.
+        for (var i = nodeIndex + 1; i < _nodes.Count; ++i)
+            _nodes[i].SetSource(null, null);
+
+        if (_mode == BindingMode.OneWayToSource)
+            return;
+
+        var errorPoint = CalculateErrorPoint(nodeIndex);
+
+        if (ShouldLogError(out var target))
+            Log(target, error, errorPoint);
+
+        // Clear the current value and publish the error.
+        var bindingError = new BindingError(
+            new BindingChainException(error, Description, errorPoint.ToString()),
+            BindingErrorType.Error);
+        ConvertAndPublishValue(AvaloniaProperty.UnsetValue, bindingError);
+    }
+
+    internal void OnDataValidationError(Exception error)
+    {
+        var bindingError = new BindingError(error, BindingErrorType.DataValidationError);
+        PublishValue(UnchangedValue, bindingError);
+    }
+
+    internal override bool WriteValueToSource(object? value)
+    {
+        if (_nodes.Count == 0 || LeafNode is not ISettableNode setter || setter.ValueType is not { } type)
+            return false;
+
+        if (Converter is { } converter &&
+            value != AvaloniaProperty.UnsetValue &&
+            value != BindingOperations.DoNothing)
+        {
+            value = ConvertBack(converter, ConverterCulture, ConverterParameter, value, type);
+        }
+
+        if (value == BindingOperations.DoNothing)
+            return true;
+
+        // Use the target type converter to convert the value to the target type if necessary.
+        if (_targetTypeConverter is not null)
+        {
+            if (_targetTypeConverter.TryConvert(value, type, ConverterCulture, out var converted))
+            {
+                value = converted;
+            }
+            else if (FallbackValue != AvaloniaProperty.UnsetValue)
+            {
+                value = FallbackValue;
+            }
+            else if (IsDataValidationEnabled)
+            {
+                var valueString = value?.ToString() ?? "(null)";
+                var valueTypeName = value?.GetType().FullName ?? "null";
+                var ex = new InvalidCastException(
+                    $"Could not convert '{valueString}' ({valueTypeName}) to {type}.");
+                OnDataValidationError(ex);
+                return false;
+            }
+            else
+            {
+                return false;
+            }
+        }
+
+        // Don't set the value if it's unchanged.
+        if (TypeUtilities.IdentityEquals(LeafNode.Value, value, type))
+            return true;
+
+        try
+        {
+            return setter.WriteValueToSource(value, _nodes);
+        }
+        catch
+        {
+            return false;
+        }
+    }
+
+    protected override bool ShouldLogError([NotNullWhen(true)] out AvaloniaObject? target)
+    {
+        if (!TryGetTarget(out target))
+            return false;
+        if (_nodes.Count > 0 && _nodes[0] is SourceNode sourceNode)
+            return sourceNode.ShouldLogErrors(target);
+        return true;
+    }
+
+    protected override void StartCore()
+    {
+        if (_source?.TryGetTarget(out var source) == true)
+        {
+            if (_nodes.Count > 0)
+                _nodes[0].SetSource(source, null);
+            else
+                ConvertAndPublishValue(source, null);
+
+            if (_mode is BindingMode.TwoWay or BindingMode.OneWayToSource &&
+                TryGetTarget(out var target) &&
+                TargetProperty is not null)
+            {
+                if (_mode is BindingMode.OneWayToSource)
+                    PublishValue(target.GetValue(TargetProperty));
+
+                var trigger = UpdateSourceTrigger;
+
+                if (trigger is UpdateSourceTrigger.PropertyChanged)
+                    target.PropertyChanged += OnTargetPropertyChanged;
+                else if (trigger is UpdateSourceTrigger.LostFocus && target is IInputElement ie)
+                    ie.LostFocus += OnTargetLostFocus;
+            }
+        }
+        else
+        {
+            OnNodeError(-1, "Binding Source is null.");
+        }
+    }
+
+    protected override void StopCore()
+    {
+        foreach (var node in _nodes)
+            node.Reset();
+
+        if (_mode is BindingMode.TwoWay or BindingMode.OneWayToSource &&
+            TryGetTarget(out var target))
+        {
+            var trigger = UpdateSourceTrigger;
+
+            if (trigger is UpdateSourceTrigger.PropertyChanged)
+                target.PropertyChanged -= OnTargetPropertyChanged;
+            else if (trigger is UpdateSourceTrigger.LostFocus && target is IInputElement ie)
+                ie.LostFocus -= OnTargetLostFocus;
+        }
+    }
+
+    private string CalculateErrorPoint(int nodeIndex)
+    {
+        // Build a string describing the binding chain up to the node that errored.
+        var result = new StringBuilder();
+
+        if (nodeIndex >= 0)
+            _nodes[nodeIndex].BuildString(result);
+        else
+            result.Append("(source)");
+
+        return result.ToString();
+    }
+
+    private void Log(AvaloniaObject target, string error, string errorPoint, LogEventLevel level = LogEventLevel.Warning)
+    {
+        if (!Logger.TryGet(level, LogArea.Binding, out var log))
+            return;
+
+        log.Log(
+            target,
+            "An error occurred binding {Property} to {Expression} at {ExpressionErrorPoint}: {Message}",
+            (object?)TargetProperty ?? "(unknown)",
+            Description,
+            errorPoint,
+            error);
+    }
+
+    private void ConvertAndPublishValue(object? value, BindingError? error)
+    {
+        var isTargetNullValue = false;
+
+        // All values other than UnsetValue and DoNothing should be passed to the converter.
+        if (Converter is { } converter &&
+            value != AvaloniaProperty.UnsetValue &&
+            value != BindingOperations.DoNothing)
+        {
+            value = Convert(converter, ConverterCulture, ConverterParameter, value, TargetType, ref error);
+        }
+
+        // Check this here as the converter may return DoNothing.
+        if (value == BindingOperations.DoNothing)
+            return;
+
+        // TargetNullValue only applies when the value is null: UnsetValue indicates that there
+        // was a binding error so we don't want to use TargetNullValue in that case.
+        if (value is null && TargetNullValue != AvaloniaProperty.UnsetValue)
+        {
+            value = ConvertFallback(TargetNullValue, nameof(TargetNullValue));
+            isTargetNullValue = true;
+        }
+
+        // If we have a value, try to convert it to the target type.
+        if (value != AvaloniaProperty.UnsetValue)
+        {
+            if (StringFormat is { } stringFormat &&
+                (TargetType == typeof(object) || TargetType == typeof(string)) &&
+                !isTargetNullValue)
+            {
+                // The string format applies if we're targeting a type that can accept a string
+                // and the value isn't the TargetNullValue.
+                value = string.Format(ConverterCulture, stringFormat, value);
+            }
+            else if (_targetTypeConverter is not null)
+            {
+                // Otherwise, if we have a target type converter, convert the value to the target type.
+                value = ConvertFrom(_targetTypeConverter, value, ref error);
+            }
+        }
+
+        // FallbackValue applies if the result from the binding, converter or target type converter
+        // is UnsetValue.
+        if (value == AvaloniaProperty.UnsetValue && FallbackValue != AvaloniaProperty.UnsetValue)
+            value = ConvertFallback(FallbackValue, nameof(FallbackValue));
+
+        // Publish the value.
+        PublishValue(value, error);
+    }
+
+    private void WriteTargetValueToSource()
+    {
+        Debug.Assert(_mode is BindingMode.TwoWay or BindingMode.OneWayToSource);
+
+        if (TryGetTarget(out var target) &&
+            TargetProperty is not null &&
+            target.GetValue(TargetProperty) is var value &&
+            !TypeUtilities.IdentityEquals(value, LeafNode.Value, TargetType))
+        {
+            WriteValueToSource(value);
+        }
+    }
+
+    private void OnTargetLostFocus(object? sender, RoutedEventArgs e)
+    {
+        Debug.Assert(UpdateSourceTrigger is UpdateSourceTrigger.LostFocus);
+
+        WriteTargetValueToSource();
+    }
+
+    private void OnTargetPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+    {
+        Debug.Assert(_mode is BindingMode.TwoWay or BindingMode.OneWayToSource);
+        Debug.Assert(UpdateSourceTrigger is UpdateSourceTrigger.PropertyChanged);
+
+        if (e.Property == TargetProperty)
+            WriteValueToSource(e.NewValue);
+    }
+
+    private object? ConvertFallback(object? fallback, string fallbackName)
+    {
+        if (_targetTypeConverter is null || TargetType == typeof(object) || fallback == AvaloniaProperty.UnsetValue)
+            return fallback;
+
+        if (_targetTypeConverter.TryConvert(fallback, TargetType, ConverterCulture, out var result))
+            return result;
+
+        if (TryGetTarget(out var target))
+            Log(target, $"Could not convert {fallbackName} '{fallback}' to '{TargetType}'.", LogEventLevel.Error);
+
+        return AvaloniaProperty.UnsetValue;
+    }
+
+    private object? ConvertFrom(TargetTypeConverter? converter, object? value, ref BindingError? error)
+    {
+        if (converter is null)
+            return value;
+
+        if (converter.TryConvert(value, TargetType, ConverterCulture, out var result))
+            return result;
+
+        var valueString = value?.ToString() ?? "(null)";
+        var valueTypeName = value?.GetType().FullName ?? "null";
+        var message = $"Could not convert '{valueString}' ({valueTypeName}) to '{TargetType}'.";
+
+        if (ShouldLogError(out var target))
+            Log(target, message, LogEventLevel.Warning);
+
+        error = new(new InvalidCastException(message), BindingErrorType.Error);
+        return AvaloniaProperty.UnsetValue;
+    }
+
+    /// <summary>
+    /// Uncommonly used fields are separated out to reduce memory usage.
+    /// </summary>
+    private class UncommonFields
+    {
+        public IValueConverter? _converter;
+        public object? _converterParameter;
+        public CultureInfo? _converterCulture;
+        public object? _fallbackValue;
+        public string? _stringFormat;
+        public object? _targetNullValue;
+        public UpdateSourceTrigger _updateSourceTrigger;
+    }
 }
diff --git a/src/Avalonia.Base/Data/Core/EmptyExpressionNode.cs b/src/Avalonia.Base/Data/Core/EmptyExpressionNode.cs
deleted file mode 100644
index b333fa904..000000000
--- a/src/Avalonia.Base/Data/Core/EmptyExpressionNode.cs
+++ /dev/null
@@ -1,7 +0,0 @@
-namespace Avalonia.Data.Core
-{
-    internal class EmptyExpressionNode : ExpressionNode
-    {
-        public override string Description => ".";
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNode.cs
deleted file mode 100644
index 30fc71cfb..000000000
--- a/src/Avalonia.Base/Data/Core/ExpressionNode.cs
+++ /dev/null
@@ -1,168 +0,0 @@
-using System;
-
-namespace Avalonia.Data.Core
-{
-    internal abstract class ExpressionNode
-    {
-        protected static readonly WeakReference<object?> UnsetReference = 
-            new WeakReference<object?>(AvaloniaProperty.UnsetValue);
-
-        protected static readonly WeakReference<object?> NullReference =
-            new WeakReference<object?>(null);
-
-        private WeakReference<object?> _target = UnsetReference;
-        private Action<object?>? _subscriber;
-        private bool _listening;
-
-        protected WeakReference<object?>? LastValue { get; private set; }
-
-        public abstract string? Description { get; }
-        public ExpressionNode? Next { get; set; }
-
-        public WeakReference<object?> Target
-        {
-            get { return _target; }
-            set
-            {
-                _ = value ?? throw new ArgumentNullException(nameof(value));
-
-                _target.TryGetTarget(out var oldTarget);
-                value.TryGetTarget(out var newTarget);
-
-                if (!ReferenceEquals(oldTarget, newTarget))
-                {
-                    if (_listening)
-                    {
-                        StopListening();
-                    }
-
-                    _target = value;
-
-                    if (_subscriber != null)
-                    {
-                        StartListening();
-                    }
-                }
-            }
-        }
-
-        public void Subscribe(Action<object?> subscriber)
-        {
-            if (_subscriber != null)
-            {
-                throw new AvaloniaInternalException("ExpressionNode can only be subscribed once.");
-            }
-
-            _subscriber = subscriber;
-            Next?.Subscribe(NextValueChanged);
-            StartListening();
-        }
-
-        public void Unsubscribe()
-        {
-            Next?.Unsubscribe();
-
-            if (_listening)
-            {
-                StopListening();
-            }
-
-            LastValue = null;
-            _subscriber = null;
-        }
-
-        protected virtual void StartListeningCore(WeakReference<object?> reference)
-        {
-            reference.TryGetTarget(out var target);
-
-            ValueChanged(target);
-        }
-
-        protected virtual void StopListeningCore()
-        {
-        }
-
-        protected virtual void NextValueChanged(object? value)
-        {
-            if (_subscriber is null)
-                return;
-
-            var bindingBroken = BindingNotification.ExtractError(value) as MarkupBindingChainException;
-            bindingBroken?.AddNode(Description ?? "{empty}");
-            _subscriber(value);
-        }
-
-        protected void ValueChanged(object? value) => ValueChanged(value, true);
-
-        private void ValueChanged(object? value, bool notify)
-        {
-            if (_subscriber is { } subscriber)
-            {
-                var notification = value as BindingNotification;
-                var next = Next;
-
-                if (notification == null)
-                {
-                    LastValue = value != null ? new WeakReference<object?>(value) : NullReference;
-                    if (next != null)
-                    {
-                        next.Target = LastValue;
-                    }
-                    else if (notify)
-                    {
-                        subscriber(value);
-                    }
-                }
-                else
-                {
-                    LastValue = notification.Value != null ? new WeakReference<object?>(notification.Value) : NullReference;
-
-                    if (next != null)
-                    {
-                        next.Target = LastValue;
-                    }
-
-                    if (next == null || notification.Error != null)
-                    {
-                        subscriber(value);
-                    }
-                }
-            }
-        }
-
-        private void StartListening()
-        {
-            _target.TryGetTarget(out var target);
-
-            if (target == null)
-            {
-                ValueChanged(TargetNullNotification());
-                _listening = false;
-            }
-            else if (target != AvaloniaProperty.UnsetValue)
-            {
-                _listening = true;
-                StartListeningCore(_target!);
-            }
-            else
-            {
-                ValueChanged(AvaloniaProperty.UnsetValue, notify:false);
-                _listening = false;
-            }
-        }
-
-        private void StopListening()
-        {
-            StopListeningCore();
-            _listening = false;
-        }
-
-        private static BindingNotification TargetNullNotification()
-        {
-            return new BindingNotification(
-                new MarkupBindingChainException("Null value"),
-                BindingErrorType.Error,
-                AvaloniaProperty.UnsetValue);
-        }
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/ArrayIndexerNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/ArrayIndexerNode.cs
new file mode 100644
index 000000000..a347a1ab7
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/ArrayIndexerNode.cs
@@ -0,0 +1,54 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+/// <summary>
+/// A node in an <see cref="BindingExpression"/> which accesses an array with integer
+/// indexers.
+/// </summary>
+internal sealed class ArrayIndexerNode : ExpressionNode, ISettableNode
+{
+    private readonly int[] _indexes;
+
+    public ArrayIndexerNode(int[] indexes)
+    {
+        _indexes = indexes;
+    }
+
+    public Type? ValueType => Source?.GetType().GetElementType();
+
+    public override void BuildString(StringBuilder builder)
+    {
+        builder.Append('[');
+
+        for (var i = 0; i < _indexes.Length; i++)
+        {
+            builder.Append(_indexes[i]);
+            if (i != _indexes.Length - 1)
+                builder.Append(',');
+        }
+
+        builder.Append(']');
+    }
+
+    public bool WriteValueToSource(object? value, IReadOnlyList<ExpressionNode> nodes)
+    {
+        if (Source is Array array)
+        {
+            array.SetValue(value, _indexes);
+            return true;
+        }
+
+        return false;
+    }
+
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        if (source is Array array)
+            SetValue(array.GetValue(_indexes));
+        else
+            ClearValue();
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/AvaloniaPropertyAccessorNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/AvaloniaPropertyAccessorNode.cs
new file mode 100644
index 000000000..d996053c2
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/AvaloniaPropertyAccessorNode.cs
@@ -0,0 +1,58 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+internal sealed class AvaloniaPropertyAccessorNode : ExpressionNode, ISettableNode
+{
+    private readonly EventHandler<AvaloniaPropertyChangedEventArgs> _onValueChanged;
+
+    public AvaloniaPropertyAccessorNode(AvaloniaProperty property)
+    {
+        Property = property;
+        _onValueChanged = OnValueChanged;
+    }
+
+    public AvaloniaProperty Property { get; }
+    public Type? ValueType => Property.PropertyType;
+
+    override public void BuildString(StringBuilder builder)
+    {
+        if (builder.Length > 0 && builder[builder.Length - 1] != '!')
+            builder.Append('.');
+        builder.Append(Property.Name);
+    }
+
+    public bool WriteValueToSource(object? value, IReadOnlyList<ExpressionNode> nodes)
+    {
+        if (Source is AvaloniaObject o)
+        {
+            o.SetValue(Property, value);
+            return true;
+        }
+
+        return false;
+    }
+
+    protected override void OnSourceChanged(object? source, Exception? dataValidationError)
+    {
+        if (source is AvaloniaObject newObject)
+        {
+            newObject.PropertyChanged += _onValueChanged;
+            SetValue(newObject.GetValue(Property));
+        }
+    }
+
+    protected override void Unsubscribe(object oldSource)
+    {
+        if (oldSource is AvaloniaObject oldObject)
+            oldObject.PropertyChanged -= _onValueChanged;
+    }
+
+    private void OnValueChanged(object? source, AvaloniaPropertyChangedEventArgs e)
+    {
+        if (e.Property == Property && source is AvaloniaObject o)
+            SetValue(o.GetValue(Property));
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/CollectionNodeBase.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/CollectionNodeBase.cs
new file mode 100644
index 000000000..db8a8e808
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/CollectionNodeBase.cs
@@ -0,0 +1,81 @@
+using System;
+using System.Collections;
+using System.Collections.Specialized;
+using System.ComponentModel;
+using Avalonia.Utilities;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+internal abstract class CollectionNodeBase : ExpressionNode,
+    IWeakEventSubscriber<NotifyCollectionChangedEventArgs>,
+    IWeakEventSubscriber<PropertyChangedEventArgs>
+{
+    void IWeakEventSubscriber<NotifyCollectionChangedEventArgs>.OnEvent(object? sender, WeakEvent ev, NotifyCollectionChangedEventArgs e)
+    {
+        if (ShouldUpdate(sender, e))
+            UpdateValueOrSetError(sender);
+    }
+
+    void IWeakEventSubscriber<PropertyChangedEventArgs>.OnEvent(object? sender, WeakEvent ev, PropertyChangedEventArgs e)
+    {
+        if (ShouldUpdate(sender, e))
+            UpdateValueOrSetError(sender);
+    }
+
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        Subscribe(source);
+        UpdateValue(source);
+    }
+
+    protected override void Unsubscribe(object source)
+    {
+        if (source is INotifyCollectionChanged incc)
+            WeakEvents.CollectionChanged.Unsubscribe(incc, this);
+        if (source is INotifyPropertyChanged inpc)
+            WeakEvents.ThreadSafePropertyChanged.Unsubscribe(inpc, this);
+    }
+
+    protected abstract bool ShouldUpdate(object? sender, PropertyChangedEventArgs e);
+    protected abstract int? TryGetFirstArgumentAsInt();
+    protected abstract void UpdateValue(object? source);
+
+    private bool ShouldUpdate(object? sender, NotifyCollectionChangedEventArgs e)
+    {
+        if (sender != Source)
+            return false;
+
+        if (sender is IList && TryGetFirstArgumentAsInt() is int index)
+        {
+            return e.Action switch
+            {
+                NotifyCollectionChangedAction.Add => index >= e.NewStartingIndex,
+                NotifyCollectionChangedAction.Remove => index >= e.OldStartingIndex,
+                NotifyCollectionChangedAction.Replace =>
+                    index >= e.NewStartingIndex &&
+                    index < e.NewStartingIndex + e.NewItems!.Count,
+                NotifyCollectionChangedAction.Move =>
+                    index >= e.NewStartingIndex && index < e.NewStartingIndex + e.NewItems!.Count ||
+                    index >= e.OldStartingIndex && index < e.OldStartingIndex + e.OldItems!.Count,
+                _ => true,
+            };
+        }
+
+        // Implementation defined meaning for the index, so just try to update anyway
+        return true;
+    }
+
+    private void Subscribe(object? source)
+    {
+        if (source is INotifyCollectionChanged incc)
+            WeakEvents.CollectionChanged.Subscribe(incc, this);
+        if (source is INotifyPropertyChanged inpc)
+            WeakEvents.ThreadSafePropertyChanged.Subscribe(inpc, this);
+    }
+
+    private void UpdateValueOrSetError(object? source)
+    {
+        try { UpdateValue(source); }
+        catch (Exception e) { SetError(e); }
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/DataContextNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/DataContextNode.cs
new file mode 100644
index 000000000..14e21d419
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/DataContextNode.cs
@@ -0,0 +1,31 @@
+using System;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+internal sealed class DataContextNode : DataContextNodeBase
+{
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        if (source is IDataContextProvider && source is AvaloniaObject ao)
+        {
+            ao.PropertyChanged += OnPropertyChanged;
+            SetValue(ao.GetValue(StyledElement.DataContextProperty));
+        }
+        else
+        {
+            SetError($"Unable to read DataContext from '{source.GetType()}'.");
+        }
+    }
+
+    protected override void Unsubscribe(object oldSource)
+    {
+        if (oldSource is StyledElement oldElement)
+            oldElement.PropertyChanged -= OnPropertyChanged;
+    }
+
+    private void OnPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+    {
+        if (sender == Source && e.Property == StyledElement.DataContextProperty)
+            SetValue(e.NewValue);
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/DataContextNodeBase.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/DataContextNodeBase.cs
new file mode 100644
index 000000000..90b684dac
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/DataContextNodeBase.cs
@@ -0,0 +1,19 @@
+using System;
+using Avalonia.LogicalTree;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+internal abstract class DataContextNodeBase : SourceNode
+{
+    public override object? SelectSource(object? source, object target, object? anchor)
+    {
+        if (source != AvaloniaProperty.UnsetValue)
+            throw new NotSupportedException(
+                "DataContextNode is invalid in conjunction with a binding source.");
+        if (target is IDataContextProvider and AvaloniaObject)
+            return target;
+        if (anchor is IDataContextProvider and AvaloniaObject)
+            return anchor;
+        throw new InvalidOperationException("Cannot find a DataContext to bind to.");
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/ExpressionNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/ExpressionNode.cs
new file mode 100644
index 000000000..e8e6633ab
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/ExpressionNode.cs
@@ -0,0 +1,253 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Reflection;
+using System.Text;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+/// <summary>
+/// A node in the binding path of an <see cref="BindingExpression"/>.
+/// </summary>
+internal abstract class ExpressionNode
+{
+    private WeakReference<object?>? _source;
+    private object? _value = AvaloniaProperty.UnsetValue;
+
+    /// <summary>
+    /// Gets the index of the node in the binding path.
+    /// </summary>
+    public int Index { get; private set; }
+
+    /// <summary>
+    /// Gets the owning <see cref="BindingExpression"/>.
+    /// </summary>
+    public BindingExpression? Owner { get; private set; }
+
+    /// <summary>
+    /// Gets the source object from which the node will read its value.
+    /// </summary>
+    public object? Source
+    {
+        get
+        {
+            if (_source?.TryGetTarget(out var source) == true)
+                return source;
+            return null;
+        }
+    }
+
+    /// <summary>
+    /// Gets the current value of the node.
+    /// </summary>
+    public object? Value => _value;
+
+    /// <summary>
+    /// Appends a string representation of the expression node to a string builder.
+    /// </summary>
+    /// <param name="builder">The string builder.</param>
+    public virtual void BuildString(StringBuilder builder) { }
+
+    /// <summary>
+    /// Builds a string representation of a binding expression.
+    /// </summary>
+    /// <param name="builder">The string builder.</param>
+    /// <param name="nodes">The nodes in the binding expression.</param>
+    public virtual void BuildString(StringBuilder builder, IReadOnlyList<ExpressionNode> nodes) 
+    {
+        if (Index > 0)
+            nodes[Index - 1].BuildString(builder, nodes);
+        BuildString(builder);
+    }
+
+    /// <summary>
+    /// Resets the node to its uninitialized state when the <see cref="Owner"/> is unsubscribed.
+    /// </summary>
+    public void Reset()
+    {
+        SetSource(null, null);
+        _source = null;
+        _value = AvaloniaProperty.UnsetValue;
+    }
+
+    /// <summary>
+    /// Sets the owner binding.
+    /// </summary>
+    /// <param name="owner">The owner binding.</param>
+    /// <param name="index">The index of the node in the binding path.</param>
+    /// <exception cref="InvalidOperationException">
+    /// The node already has an owner.
+    /// </exception>
+    public void SetOwner(BindingExpression owner, int index)
+    {
+        if (Owner is not null)
+            throw new InvalidOperationException($"{this} already has an owner.");
+        Owner = owner;
+        Index = index;
+    }
+
+    /// <summary>
+    /// Sets the <see cref="Source"/> from which the node will read its value and updates
+    /// the current <see cref="Value"/>, notifying the <see cref="Owner"/> if the value
+    /// changes.
+    /// </summary>
+    /// <param name="source">
+    /// The new source from which the node will read its value. May be 
+    /// <see cref="AvaloniaProperty.UnsetValue"/> in which case the source will be considered
+    /// to be null.
+    /// </param>
+    /// <param name="dataValidationError">
+    /// Any data validation error reported by the previous expression node.
+    /// </param>
+    public void SetSource(object? source, Exception? dataValidationError)
+    {
+        var oldSource = Source;
+
+        if (source == AvaloniaProperty.UnsetValue)
+            source = null;
+
+        if (source == oldSource)
+            return;
+
+        if (oldSource is not null)
+            Unsubscribe(oldSource);
+
+        _source = new(source);
+
+        if (source is null)
+        {
+            // If the source is null then the value is null. We explicitly do not want to call
+            // OnSourceChanged as we don't want to raise errors for subsequent nodes in the
+            // binding change.
+            _value = AvaloniaProperty.UnsetValue;
+        }
+        else
+        {
+            try { OnSourceChanged(source, dataValidationError); }
+            catch (Exception e) { SetError(e); }
+        }
+    }
+
+    /// <summary>
+    /// Sets the current value to <see cref="AvaloniaProperty.UnsetValue"/>.
+    /// </summary>
+    protected void ClearValue() => SetValue(AvaloniaProperty.UnsetValue);
+
+    /// <summary>
+    /// Notifies the <see cref="Owner"/> of a data validation error.
+    /// </summary>
+    /// <param name="error">The error.</param>
+    protected void SetDataValidationError(Exception error)
+    {
+        if (error is TargetInvocationException tie)
+            error = tie.InnerException!;
+        Owner?.OnDataValidationError(error);
+    }
+
+    /// <summary>
+    /// Sets the current value to <see cref="AvaloniaProperty.UnsetValue"/> and notifies the
+    /// <see cref="Owner"/> of the error.
+    /// </summary>
+    /// <param name="message">The error message.</param>
+    protected void SetError(string message)
+    {
+        _value = AvaloniaProperty.UnsetValue;
+        Owner?.OnNodeError(Index, message);
+    }
+
+    /// <summary>
+    /// Sets the current value to <see cref="AvaloniaProperty.UnsetValue"/> and notifies the
+    /// <see cref="Owner"/> of the error.
+    /// </summary>
+    /// <param name="e">The error.</param>
+    protected void SetError(Exception e)
+    {
+        if (e is TargetInvocationException tie)
+            e = tie.InnerException!;
+        if (e is AggregateException ae && ae.InnerExceptions.Count == 1)
+            e = e.InnerException!;
+        SetError(e.Message);
+    }
+
+    /// <summary>
+    /// Sets the current <see cref="Value"/>, notifying the <see cref="Owner"/> if the value
+    /// has changed.
+    /// </summary>
+    /// <param name="valueOrNotification">
+    /// The new value. May be a <see cref="BindingNotification"/>.
+    /// </param>
+    protected void SetValue(object? valueOrNotification)
+    {
+        if (valueOrNotification is BindingNotification notification)
+        {
+            if (notification.ErrorType == BindingErrorType.Error)
+            {
+                SetError(notification.Error!);
+            }
+            else if (notification.ErrorType == BindingErrorType.DataValidationError)
+            {
+                if (notification.HasValue)
+                    SetValue(notification.Value, notification.Error);
+                else
+                    SetDataValidationError(notification.Error!);
+            }
+            else
+            {
+                SetValue(notification.Value, null);
+            }
+        }
+        else
+        {
+            SetValue(valueOrNotification, null);
+        }
+    }
+
+    /// <summary>
+    /// Sets the current <see cref="Value"/>, notifying the <see cref="Owner"/> if the value
+    /// has changed.
+    /// </summary>
+    /// <param name="value">
+    /// The new value. May not be a <see cref="BindingNotification"/>.
+    /// </param>
+    /// <param name="dataValidationError">
+    /// The data validation error associated with the new value, if any.
+    /// </param>
+    protected void SetValue(object? value, Exception? dataValidationError = null)
+    {
+        Debug.Assert(value is not BindingNotification);
+
+        if (Owner is null)
+            return;
+
+        // We raise a change notification if:
+        //
+        // - This is the initial value (_value is null)
+        // - There is a data validation error
+        // - There is no data validation error, but the owner has one
+        // - The new value is different to the old value
+        if (_value is null ||
+            dataValidationError is not null ||
+            (dataValidationError is null && Owner.ErrorType == BindingErrorType.DataValidationError) ||
+            !Equals(value, _value))
+        {
+            _value = value;
+            Owner.OnNodeValueChanged(Index, value, dataValidationError);
+        }
+    }
+
+    /// <summary>
+    /// When implemented in a derived class, subscribes to the new source, and updates the current 
+    /// <see cref="Value"/>.
+    /// </summary>
+    /// <param name="source">The new source.</param>
+    /// <param name="dataValidationError">
+    /// Any data validation error reported by the previous expression node.
+    /// </param>
+    protected abstract void OnSourceChanged(object source, Exception? dataValidationError);
+
+    /// <summary>
+    /// When implemented in a derived class, unsubscribes from the previous source.
+    /// </summary>
+    /// <param name="oldSource">The old source.</param>
+    protected virtual void Unsubscribe(object oldSource) { }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/FuncTransformNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/FuncTransformNode.cs
new file mode 100644
index 000000000..7ad0b7ee9
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/FuncTransformNode.cs
@@ -0,0 +1,28 @@
+using System;
+using System.Text;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+/// <summary>
+/// A node in an <see cref="BindingExpression"/> which uses a function to transform its
+/// value.
+/// </summary>
+internal sealed class FuncTransformNode : ExpressionNode
+{
+    private readonly Func<object?, object?> _transform;
+
+    public FuncTransformNode(Func<object?, object?> transform)
+    {
+        _transform = transform;
+    }
+
+    public override void BuildString(StringBuilder builder)
+    {
+        // We don't have enough information to add anything here.
+    }
+
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        SetValue(_transform(source));
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/IPropertyAccessorNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/IPropertyAccessorNode.cs
new file mode 100644
index 000000000..04f72ceea
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/IPropertyAccessorNode.cs
@@ -0,0 +1,13 @@
+using Avalonia.Data.Core.Plugins;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+/// <summary>
+/// Indicates that a <see cref="ExpressionNode"/> accesses a property on an object.
+/// </summary>
+internal interface IPropertyAccessorNode
+{
+    string PropertyName { get; }
+    IPropertyAccessor? Accessor { get; }
+    void EnableDataValidation();
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/ISettableNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/ISettableNode.cs
new file mode 100644
index 000000000..e2bf5c3df
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/ISettableNode.cs
@@ -0,0 +1,23 @@
+using System;
+using System.Collections.Generic;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+/// <summary>
+/// An <see cref="ExpressionNode"/> that can write a value to its source.
+/// </summary>
+internal interface ISettableNode
+{
+    /// <summary>
+    /// Gets the type of the value accepted by the node, or null if the node is not settable.
+    /// </summary>
+    Type? ValueType { get; }
+
+    /// <summary>
+    /// Tries to write the specified value to the source.
+    /// </summary>
+    /// <param name="value">The value to write.</param>
+    /// <param name="nodes">The expression nodes in the binding.</param>
+    /// <returns>True if the value was written sucessfully; otherwise false.</returns>
+    bool WriteValueToSource(object? value, IReadOnlyList<ExpressionNode> nodes);
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/LogicalAncestorElementNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/LogicalAncestorElementNode.cs
new file mode 100644
index 000000000..ccf6c76f9
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/LogicalAncestorElementNode.cs
@@ -0,0 +1,85 @@
+using System;
+using System.Text;
+using Avalonia.LogicalTree;
+using Avalonia.Reactive;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+internal sealed class LogicalAncestorElementNode : SourceNode
+{
+    private readonly Type? _ancestorType;
+    private readonly int _ancestorLevel;
+    private IDisposable? _subscription;
+
+    public LogicalAncestorElementNode(Type? ancestorType, int ancestorLevel)
+    {
+        _ancestorType = ancestorType;
+        _ancestorLevel = ancestorLevel;
+    }
+
+    public override void BuildString(StringBuilder builder)
+    {
+        builder.Append("$parent");
+
+        if (_ancestorLevel > 0 || _ancestorType is not null)
+        {
+            builder.Append('[');
+
+            if (_ancestorType is not null)
+            {
+                builder.Append(_ancestorType.Name);
+                if (_ancestorLevel > 0)
+                    builder.Append(',');
+            }
+
+            if (_ancestorLevel > 0)
+                builder.Append(_ancestorLevel);
+
+            builder.Append(']');
+        }
+    }
+
+    public override object? SelectSource(object? source, object target, object? anchor)
+    {
+        if (source != AvaloniaProperty.UnsetValue)
+            throw new NotSupportedException(
+                "LogicalAncestorNode is invalid in conjunction with a binding source.");
+        if (target is ILogical)
+            return target;
+        if (anchor is ILogical)
+            return anchor;
+        throw new InvalidOperationException("Cannot find an ILogical to get a logical ancestor.");
+    }
+
+    public override bool ShouldLogErrors(object target)
+    {
+        return target is ILogical logical && logical.IsAttachedToLogicalTree;
+    }
+
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        if (source is ILogical logical)
+        {
+            var locator = ControlLocator.Track(logical, _ancestorLevel, _ancestorType);
+            _subscription = locator.Subscribe(TrackedControlChanged);
+        }
+    }
+
+    protected override void Unsubscribe(object oldSource)
+    {
+        _subscription?.Dispose();
+        _subscription = null;
+    }
+
+    private void TrackedControlChanged(ILogical? control)
+    {
+        if (control is not null)
+        {
+            SetValue(control);
+        }
+        else
+        {
+            SetError("Ancestor not found.");
+        }
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/LogicalNotNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/LogicalNotNode.cs
new file mode 100644
index 000000000..bb65ac16d
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/LogicalNotNode.cs
@@ -0,0 +1,69 @@
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using System.Text;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+internal sealed class LogicalNotNode : ExpressionNode, ISettableNode
+{
+    public override void BuildString(StringBuilder builder)
+    {
+        builder.Append("!");
+    }
+
+    public override void BuildString(StringBuilder builder, IReadOnlyList<ExpressionNode> nodes)
+    {
+        builder.Append("!");
+        if (Index > 0)
+            nodes[Index - 1].BuildString(builder, nodes);
+    }
+
+    public Type ValueType => typeof(bool);
+
+    public bool WriteValueToSource(object? value, IReadOnlyList<ExpressionNode> nodes)
+    {
+        if (Index > 0 && nodes[Index - 1] is ISettableNode previousNode && TryConvert(value, out var boolValue))
+            return previousNode.WriteValueToSource(!boolValue, nodes);
+        return false;
+    }
+
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        var v = BindingNotification.ExtractValue(source);
+
+        if (TryConvert(v, out var value))
+        {
+            SetValue(BindingNotification.UpdateValue(source, !value), dataValidationError);
+        }
+        else
+            SetError($"Unable to convert '{source}' to bool.");
+    }
+
+    private static bool TryConvert(object? value, out bool result)
+    {
+        if (value is bool b)
+        {
+            result = b;
+            return true;
+        }
+        if (value is string s)
+        {
+            // Special case string for performance.
+            if (bool.TryParse(s, out result))
+                return true;
+        }
+        else
+        {
+            try
+            {
+                result = Convert.ToBoolean(value, CultureInfo.InvariantCulture);
+                return true;
+            }
+            catch { }
+        }
+
+        result = false;
+        return false;
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/MethodCommandNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/MethodCommandNode.cs
new file mode 100644
index 000000000..6eccd5238
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/MethodCommandNode.cs
@@ -0,0 +1,107 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Text;
+using System.Windows.Input;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+/// <summary>
+/// A node in an <see cref="BindingExpression"/> which converts methods to an
+/// <see cref="ICommand"/>.
+/// </summary>
+internal sealed class MethodCommandNode : ExpressionNode
+{
+    private readonly string _methodName;
+    private readonly Action<object, object?> _execute;
+    private readonly Func<object, object?, bool>? _canExecute;
+    private readonly ISet<string> _dependsOnProperties;
+    private Command? _command;
+
+    public MethodCommandNode(
+        string methodName,
+        Action<object, object?> execute,
+        Func<object, object?, bool>? canExecute,
+        ISet<string> dependsOnProperties)
+    {
+        _methodName = methodName;
+        _execute = execute;
+        _canExecute = canExecute;
+        _dependsOnProperties = dependsOnProperties;
+    }
+
+    public override void BuildString(StringBuilder builder)
+    {
+        if (builder.Length > 0 && builder[builder.Length - 1] != '!')
+            builder.Append('.');
+        builder.Append(_methodName);
+        builder.Append("()");
+    }
+
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        if (source is INotifyPropertyChanged newInpc)
+            newInpc.PropertyChanged += OnPropertyChanged;
+
+        _command = new Command(source, _execute, _canExecute);
+        SetValue(_command);
+    }
+
+    protected override void Unsubscribe(object oldSource)
+    {
+        if (oldSource is INotifyPropertyChanged oldInpc)
+            oldInpc.PropertyChanged -= OnPropertyChanged;
+    }
+
+    private void OnPropertyChanged(object? sender, PropertyChangedEventArgs e)
+    {
+        if (string.IsNullOrEmpty(e.PropertyName) || _dependsOnProperties.Contains(e.PropertyName))
+        {
+            _command?.RaiseCanExecuteChanged();
+        }
+    }
+
+    private sealed class Command : ICommand
+    {
+        private readonly WeakReference<object?> _target;
+        private readonly Action<object, object?> _execute;
+        private readonly Func<object, object?, bool>? _canExecute;
+
+        public event EventHandler? CanExecuteChanged;
+
+        public Command(object? target, Action<object, object?> execute, Func<object, object?, bool>? canExecute)
+        {
+            _target = new(target);
+            _execute = execute;
+            _canExecute = canExecute;
+        }
+
+        public void RaiseCanExecuteChanged()
+        {
+            Threading.Dispatcher.UIThread.Post(() => CanExecuteChanged?.Invoke(this, EventArgs.Empty)
+               , Threading.DispatcherPriority.Input);
+        }
+
+        public bool CanExecute(object? parameter)
+        {
+            if (_target.TryGetTarget(out var target))
+            {
+                if (_canExecute == null)
+                {
+                    return true;
+                }
+                return _canExecute(target, parameter);
+            }
+            return false;
+        }
+
+        public void Execute(object? parameter)
+        {
+            if (_target.TryGetTarget(out var target))
+            {
+                _execute(target, parameter);
+            }
+        }
+    }
+
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/NamedElementNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/NamedElementNode.cs
new file mode 100644
index 000000000..5f7b96514
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/NamedElementNode.cs
@@ -0,0 +1,46 @@
+using System;
+using System.Text;
+using Avalonia.Controls;
+using Avalonia.LogicalTree;
+using Avalonia.Reactive;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+internal sealed class NamedElementNode : SourceNode
+{
+    private readonly WeakReference<INameScope?> _nameScope;
+    private readonly string _name;
+    private IDisposable? _subscription;
+
+    public NamedElementNode(INameScope? nameScope, string name)
+    {
+        _nameScope = new(nameScope);
+        _name = name;
+    }
+
+    public override void BuildString(StringBuilder builder)
+    {
+        builder.Append('#');
+        builder.Append(_name);
+    }
+
+    public override bool ShouldLogErrors(object target)
+    {
+        // We don't log errors when the target element isn't rooted.
+        return target is not ILogical logical || logical.IsAttachedToLogicalTree;
+    }
+
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        if (_nameScope.TryGetTarget(out var scope))
+            _subscription = NameScopeLocator.Track(scope, _name).Subscribe(SetValue);
+        else
+            SetError("NameScope not found.");
+    }
+
+    protected override void Unsubscribe(object oldSource)
+    {
+        _subscription?.Dispose();
+        _subscription = null;
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/ParentDataContextNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/ParentDataContextNode.cs
new file mode 100644
index 000000000..76820e212
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/ParentDataContextNode.cs
@@ -0,0 +1,67 @@
+using System;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+/// <summary>
+/// A node in an <see cref="BindingExpression"/> which selects the value of the visual
+/// parent's DataContext.
+/// </summary>
+internal sealed class ParentDataContextNode : DataContextNodeBase
+{
+    private static readonly AvaloniaObject s_unset = new();
+    private AvaloniaObject? _parent = s_unset;
+
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        if (source is AvaloniaObject newElement)
+            newElement.PropertyChanged += OnPropertyChanged;
+
+        if (source is Visual v)
+            SetParent(v.GetValue(Visual.VisualParentProperty));
+        else
+            SetParent(null);
+    }
+
+    protected override void Unsubscribe(object oldSource)
+    {
+        if (oldSource is AvaloniaObject oldElement)
+            oldElement.PropertyChanged -= OnPropertyChanged;
+    }
+
+    private void SetParent(AvaloniaObject? parent)
+    {
+        if (parent == _parent)
+            return;
+
+        Unsubscribe();
+        _parent = parent;
+
+        if (_parent is IDataContextProvider)
+        {
+            _parent.PropertyChanged += OnParentPropertyChanged;
+            SetValue(_parent.GetValue(StyledElement.DataContextProperty));
+        }
+        else
+        {
+            SetValue(null);
+        }
+    }
+
+    private void Unsubscribe()
+    {
+        if (_parent is not null)
+            _parent.PropertyChanged -= OnParentPropertyChanged;
+    }
+
+    private void OnPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+    {
+        if (e.Property == Visual.VisualParentProperty)
+            SetParent(e.NewValue as AvaloniaObject);
+    }
+
+    private void OnParentPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+    {
+        if (e.Property == StyledElement.DataContextProperty)
+            SetValue(e.NewValue);
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/PropertyAccessorNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/PropertyAccessorNode.cs
new file mode 100644
index 000000000..9ddc4705b
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/PropertyAccessorNode.cs
@@ -0,0 +1,85 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Text;
+using Avalonia.Data.Core.Plugins;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+/// <summary>
+/// A node in the binding path of an <see cref="BindingExpression"/> that reads a property
+/// via a predefined <see cref="IPropertyAccessorPlugin"/>.
+/// </summary>
+internal sealed class PropertyAccessorNode : ExpressionNode, IPropertyAccessorNode, ISettableNode
+{
+    private readonly Action<object?> _onValueChanged;
+    private readonly IPropertyAccessorPlugin _plugin;
+    private IPropertyAccessor? _accessor;
+    private bool _enableDataValidation;
+
+    public PropertyAccessorNode(string propertyName, IPropertyAccessorPlugin plugin)
+    {
+        _plugin = plugin;
+        _onValueChanged = OnValueChanged;
+        PropertyName = propertyName;
+    }
+
+    public IPropertyAccessor? Accessor => _accessor;
+    public string PropertyName { get; }
+    public Type? ValueType => _accessor?.PropertyType;
+
+    public override void BuildString(StringBuilder builder)
+    {
+        if (builder.Length > 0 && builder[builder.Length - 1] != '!')
+            builder.Append('.');
+        builder.Append(PropertyName);
+    }
+
+    public void EnableDataValidation() => _enableDataValidation = true;
+
+    public bool WriteValueToSource(object? value, IReadOnlyList<ExpressionNode> nodes)
+    {
+        if (_accessor?.PropertyType is not null)
+        {
+            return _accessor.SetValue(value, BindingPriority.LocalValue);
+        }
+
+        return false;
+    }
+
+    [UnconditionalSuppressMessage("Trimming", "IL2026:Members annotated with 'RequiresUnreferencedCodeAttribute' require dynamic access otherwise can break functionality when trimming application code", Justification = "<Pending>")]
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        var reference = new WeakReference<object?>(source);
+
+        if (_plugin.Start(reference, PropertyName) is { } accessor)
+        {
+            if (_enableDataValidation)
+            {
+                foreach (var validator in BindingPlugins.s_dataValidators)
+                {
+                    if (validator.Match(reference, PropertyName))
+                        accessor = validator.Start(reference, PropertyName, accessor);
+                }
+            }
+
+            _accessor = accessor;
+            _accessor.Subscribe(_onValueChanged);
+        }
+        else
+        {
+            ClearValue();
+        }
+    }
+
+    protected override void Unsubscribe(object oldSource)
+    {
+        _accessor?.Dispose();
+        _accessor = null;
+    }
+
+    private void OnValueChanged(object? newValue)
+    {
+        SetValue(newValue);
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/DynamicPluginPropertyAccessorNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/DynamicPluginPropertyAccessorNode.cs
new file mode 100644
index 000000000..d1ecc1320
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/DynamicPluginPropertyAccessorNode.cs
@@ -0,0 +1,95 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Text;
+using Avalonia.Data.Core.Plugins;
+
+namespace Avalonia.Data.Core.ExpressionNodes.Reflection;
+
+/// <summary>
+/// A node in the binding path of an <see cref="BindingExpression"/> that reads a property
+/// via an <see cref="IPropertyAccessorPlugin"/> selected at runtime from the registered
+/// <see cref="BindingPlugins.PropertyAccessors"/>.
+/// </summary>
+[RequiresUnreferencedCode(TrimmingMessages.ExpressionNodeRequiresUnreferencedCodeMessage)]
+internal sealed class DynamicPluginPropertyAccessorNode : ExpressionNode, IPropertyAccessorNode, ISettableNode
+{
+    private readonly Action<object?> _onValueChanged;
+    private IPropertyAccessor? _accessor;
+    private bool _enableDataValidation;
+
+    public DynamicPluginPropertyAccessorNode(string propertyName)
+    {
+        _onValueChanged = OnValueChanged;
+        PropertyName = propertyName;
+    }
+
+    public IPropertyAccessor? Accessor => _accessor;
+    public string PropertyName { get; }
+    public Type? ValueType => _accessor?.PropertyType;
+
+    override public void BuildString(StringBuilder builder)
+    {
+        if (builder.Length > 0 && builder[builder.Length - 1] != '!')
+            builder.Append('.');
+        builder.Append(PropertyName);
+    }
+
+    public void EnableDataValidation() => _enableDataValidation = true;
+
+    public bool WriteValueToSource(object? value, IReadOnlyList<ExpressionNode> nodes)
+    {
+        return _accessor?.SetValue(value, BindingPriority.LocalValue) ?? false;
+    }
+
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        var reference = new WeakReference<object?>(source);
+
+        if (GetPlugin(source) is { } plugin &&
+            plugin.Start(reference, PropertyName) is { } accessor)
+        {
+            if (_enableDataValidation)
+            {
+                foreach (var validator in BindingPlugins.s_dataValidators)
+                {
+                    if (validator.Match(reference, PropertyName))
+                        accessor = validator.Start(reference, PropertyName, accessor);
+                }
+            }
+
+            _accessor = accessor;
+            _accessor.Subscribe(_onValueChanged);
+        }
+        else
+        {
+            SetError(
+                $"Could not find a matching property accessor for '{PropertyName}' on '{source.GetType()}'.");
+        }
+    }
+
+    protected override void Unsubscribe(object oldSource)
+    {
+        _accessor?.Dispose();
+        _accessor = null;
+    }
+
+    private void OnValueChanged(object? newValue)
+    {
+        SetValue(newValue);
+    }
+
+    private IPropertyAccessorPlugin? GetPlugin(object? source)
+    {
+        if (source is null)
+            return null;
+
+        foreach (var plugin in BindingPlugins.s_propertyAccessors)
+        {
+            if (plugin.Match(source, PropertyName))
+                return plugin;
+        }
+
+        return null;
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/DynamicPluginStreamNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/DynamicPluginStreamNode.cs
new file mode 100644
index 000000000..70b0f710a
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/DynamicPluginStreamNode.cs
@@ -0,0 +1,53 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.Text;
+using Avalonia.Data.Core.Plugins;
+using Avalonia.Reactive;
+
+namespace Avalonia.Data.Core.ExpressionNodes.Reflection;
+
+[RequiresUnreferencedCode(TrimmingMessages.ExpressionNodeRequiresUnreferencedCodeMessage)]
+internal sealed class DynamicPluginStreamNode : ExpressionNode
+{
+    private IDisposable? _subscription;
+
+    override public void BuildString(StringBuilder builder)
+    {
+        builder.Append('^');
+    }
+
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        var reference = new WeakReference<object?>(source);
+
+        if (GetPlugin(reference) is { } plugin &&
+            plugin.Start(reference) is { } accessor)
+        {
+            _subscription = accessor.Subscribe(SetValue);
+        }
+        else
+        {
+            SetValue(null);
+        }
+    }
+
+    protected override void Unsubscribe(object oldSource)
+    {
+        _subscription?.Dispose();
+        _subscription = null;
+    }
+
+    private static IStreamPlugin? GetPlugin(WeakReference<object?> source)
+    {
+        if (source is null)
+            return null;
+
+        foreach (var plugin in BindingPlugins.s_streamHandlers)
+        {
+            if (plugin.Match(source))
+                return plugin;
+        }
+
+        return null;
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/ExpressionTreeIndexerNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/ExpressionTreeIndexerNode.cs
new file mode 100644
index 000000000..e720aa6e6
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/ExpressionTreeIndexerNode.cs
@@ -0,0 +1,81 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq.Expressions;
+using System.Text;
+
+namespace Avalonia.Data.Core.ExpressionNodes.Reflection;
+
+[RequiresUnreferencedCode(TrimmingMessages.ExpressionNodeRequiresUnreferencedCodeMessage)]
+internal sealed class ExpressionTreeIndexerNode : CollectionNodeBase, ISettableNode
+{
+    private readonly ParameterExpression _parameter;
+    private readonly IndexExpression _expression;
+    private readonly Delegate _setDelegate;
+    private readonly Delegate _getDelegate;
+    private readonly Delegate _firstArgumentDelegate;
+
+    public ExpressionTreeIndexerNode(IndexExpression expression)
+    {
+        var valueParameter = Expression.Parameter(expression.Type);
+        _parameter = Expression.Parameter(expression.Object!.Type);
+        _expression = expression.Update(_parameter, expression.Arguments);
+        _getDelegate = Expression.Lambda(_expression, _parameter).Compile();
+        _setDelegate = Expression.Lambda(Expression.Assign(_expression, valueParameter), _parameter, valueParameter).Compile();
+        _firstArgumentDelegate = Expression.Lambda(_expression.Arguments[0], _parameter).Compile();
+    }
+
+    public Type? ValueType => _expression.Type;
+
+    public override void BuildString(StringBuilder builder)
+    {
+        builder.Append('[');
+        
+        for (var i = 1; i < _expression.Arguments.Count; ++i)
+        {
+            if (i > 1)
+                builder.Append(", ");
+            builder.Append(_expression.Arguments[i]);
+        }
+
+        builder.Append(_expression.Arguments[0]);
+        builder.Append(']');
+    }
+
+    public bool WriteValueToSource(object? value, IReadOnlyList<ExpressionNode> nodes)
+    {
+        if (Source is null)
+            return false;
+        _setDelegate.DynamicInvoke(Source, value);
+        return true;
+    }
+
+    protected override bool ShouldUpdate(object? sender, PropertyChangedEventArgs e)
+    {
+        return _expression.Indexer == null || _expression.Indexer.Name == e.PropertyName;
+    }
+
+    protected override int? TryGetFirstArgumentAsInt()
+    {
+        var source = Source;
+        if (source is null)
+            return null;
+        return _firstArgumentDelegate.DynamicInvoke(source) as int?;
+    }
+
+    protected override void UpdateValue(object? source)
+    {
+        try
+        {
+            if (source is not null)
+                SetValue(_getDelegate.DynamicInvoke(source));
+            else
+                SetValue(null);
+        }
+        catch (Exception e)
+        {
+            SetError(e);
+        }
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/ReflectionIndexerNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/ReflectionIndexerNode.cs
new file mode 100644
index 000000000..16b9cda49
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/ReflectionIndexerNode.cs
@@ -0,0 +1,159 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Diagnostics.CodeAnalysis;
+using System.Globalization;
+using System.Linq;
+using System.Reflection;
+using System.Text;
+using Avalonia.Input;
+using Avalonia.Utilities;
+
+namespace Avalonia.Data.Core.ExpressionNodes.Reflection;
+
+[RequiresUnreferencedCode(TrimmingMessages.ReflectionBindingRequiresUnreferencedCodeMessage)]
+internal sealed class ReflectionIndexerNode : CollectionNodeBase, ISettableNode
+{
+    private static readonly BindingFlags InstanceFlags = BindingFlags.Instance | BindingFlags.Public | BindingFlags.DeclaredOnly;
+    private MethodInfo? _getter;
+    private MethodInfo? _setter;
+    private object?[]? _indexes;
+
+    public ReflectionIndexerNode(IList arguments)
+    {
+        Arguments = arguments;
+    }
+
+    public IList Arguments { get; }
+    public Type? ValueType => _getter?.ReturnType;
+
+    public override void BuildString(StringBuilder builder)
+    {
+        builder.Append('[');
+        for (var i = 0; i < Arguments.Count; i++)
+        {
+            builder.Append(Arguments[i]);
+            if (i != Arguments.Count - 1)
+                builder.Append(',');
+        }
+        builder.Append(']');
+    }
+
+    public bool WriteValueToSource(object? value, IReadOnlyList<ExpressionNode> nodes)
+    {
+        if (Source is null || _setter is null)
+            return false;
+
+        var args = new object?[_indexes!.Length + 1];
+        _indexes.CopyTo(args, 0);
+        args[_indexes.Length] = value;
+        _setter.Invoke(Source, args);
+        return true;
+    }
+
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        _indexes = null;
+
+        if (GetIndexer(source.GetType(), out _getter, out _setter))
+        {
+            var parameters = _getter.GetParameters();
+            
+            if (parameters.Length != Arguments.Count)
+            {
+                SetError($"Wrong number of arguments for indexer: expected {parameters.Length}, got {Arguments.Count}.");
+                return;
+            }
+            
+            _indexes = ConvertIndexes(parameters, Arguments);
+            base.OnSourceChanged(source, dataValidationError);
+        }
+        else
+        {
+            SetError($"Type '{source.GetType()}' does not have an indexer.");
+        }
+    }
+
+    protected override bool ShouldUpdate(object? sender, PropertyChangedEventArgs e)
+    {
+        if (sender is null || e.PropertyName is null)
+            return false;
+        var typeInfo = sender.GetType().GetTypeInfo();
+        return typeInfo.GetDeclaredProperty(e.PropertyName)?.GetIndexParameters().Any() ?? false;
+    }
+
+    protected override int? TryGetFirstArgumentAsInt()
+    {
+        if (TypeUtilities.TryConvert(typeof(int), Arguments[0], CultureInfo.InvariantCulture, out var value))
+            return (int?)value;
+        return null;
+    }
+
+    protected override void UpdateValue(object? source)
+    {
+        if (_getter is not null && _indexes is not null)
+            SetValue(_getter.Invoke(source, _indexes));
+        else
+            ClearValue();
+    }
+
+    private static object?[] ConvertIndexes(ParameterInfo[] indexParameters, IList arguments)
+    {
+        var result = new List<object?>();
+
+        for (var i = 0; i < indexParameters.Length; i++)
+        {
+            var type = indexParameters[i].ParameterType;
+            var argument = arguments[i];
+
+            if (TypeUtilities.TryConvert(type, argument, CultureInfo.InvariantCulture, out var value))
+                result.Add(value);
+            else
+                throw new InvalidCastException(
+                    $"Could not convert list index '{i}' of type '{argument}' to '{type}'.");
+        }
+
+        return result.ToArray();
+    }
+
+    private static bool GetIndexer(Type? type, [NotNullWhen(true)] out MethodInfo? getter, out MethodInfo? setter)
+    {
+        getter = setter = null;
+
+        if (type is null)
+            return false;
+
+        if (type.IsArray)
+        {
+            getter = type.GetMethod("Get");
+            setter = type.GetMethod("Set");
+            return getter is not null;
+        }
+
+        for (; type != null; type = type.BaseType)
+        {
+            // check for the default indexer name first to make this faster.
+            // this will only be false when a class in vb has a custom indexer name.
+            if (type.GetProperty(CommonPropertyNames.IndexerName, InstanceFlags) is { } indexer)
+            {
+                getter = indexer.GetMethod;
+                setter = indexer.SetMethod;
+                return getter is not null;
+            }
+
+            foreach (var property in type.GetProperties(InstanceFlags))
+            {
+                if (property.GetIndexParameters().Length > 0)
+                {
+                    getter = property.GetMethod;
+                    setter = property.SetMethod;
+                    return getter is not null;
+                }
+            }
+        }
+
+        return false;
+    }
+
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/ReflectionTypeCastNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/ReflectionTypeCastNode.cs
new file mode 100644
index 000000000..c973d9d23
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/Reflection/ReflectionTypeCastNode.cs
@@ -0,0 +1,29 @@
+using System;
+using System.Text;
+
+namespace Avalonia.Data.Core.ExpressionNodes.Reflection;
+
+/// <summary>
+/// A node in an <see cref="BindingExpression"/> which casts a value using reflection.
+/// </summary>
+internal sealed class ReflectionTypeCastNode : ExpressionNode
+{
+    private readonly Type _targetType;
+
+    public ReflectionTypeCastNode(Type targetType) => _targetType = targetType;
+
+    public override void BuildString(StringBuilder builder)
+    {
+        builder.Append('(');
+        builder.Append(_targetType.Name);
+        builder.Append(')');
+    }
+
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        if (_targetType.IsInstanceOfType(source))
+            SetValue(source);
+        else
+            ClearValue();
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/SourceNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/SourceNode.cs
new file mode 100644
index 000000000..3608611fd
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/SourceNode.cs
@@ -0,0 +1,26 @@
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+/// <summary>
+/// A node in a binding expression which represents the source of the binding, e.g. DataContext,
+/// logical ancestor.
+/// </summary>
+internal abstract class SourceNode : ExpressionNode
+{
+    /// <summary>
+    /// Selects the source for the binding expression based on the binding source, target and
+    /// anchor.
+    /// </summary>
+    /// <param name="source">The binding source.</param>
+    /// <param name="target">The binding target.</param>
+    /// <param name="anchor">The anchor.</param>
+    /// <returns>The source for the binding expression.</returns>
+    public virtual object? SelectSource(object? source, object target, object? anchor)
+    {
+        return source != AvaloniaProperty.UnsetValue ? source : target;
+    }
+
+    public virtual bool ShouldLogErrors(object target)
+    {
+        return Value is not null;
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/StreamNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/StreamNode.cs
new file mode 100644
index 000000000..19e5a5882
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/StreamNode.cs
@@ -0,0 +1,43 @@
+using System;
+using System.Text;
+using Avalonia.Data.Core.Plugins;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+internal sealed class StreamNode : ExpressionNode, IObserver<object?>
+{
+    private IStreamPlugin _plugin;
+    private IDisposable? _subscription;
+
+    public StreamNode(IStreamPlugin plugin)
+    {
+        _plugin = plugin;
+    }
+
+    public override void BuildString(StringBuilder builder)
+    {
+        builder.Append('^');
+    }
+
+    void IObserver<object?>.OnCompleted() { }
+    void IObserver<object?>.OnError(Exception error) { }
+    void IObserver<object?>.OnNext(object? value) => SetValue(value);
+
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        if (_plugin.Start(new(source)) is { } accessor)
+        {
+            _subscription = accessor.Subscribe(this);
+        }
+        else
+        {
+            ClearValue();
+        }
+    }
+
+    protected override void Unsubscribe(object oldSource)
+    {
+        _subscription?.Dispose();
+        _subscription = null;
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/TemplatedParentNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/TemplatedParentNode.cs
new file mode 100644
index 000000000..6e81a01ce
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/TemplatedParentNode.cs
@@ -0,0 +1,49 @@
+using System;
+using System.Text;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+internal sealed class TemplatedParentNode : SourceNode
+{
+    public override void BuildString(StringBuilder builder)
+    {         
+        builder.Append("$templatedParent");
+    }
+
+    public override object? SelectSource(object? source, object target, object? anchor)
+    {
+        if (source != AvaloniaProperty.UnsetValue)
+            throw new NotSupportedException(
+                "TemplatedParentNode is invalid in conjunction with a binding source.");
+        if (target is StyledElement)
+            return target;
+        if (anchor is StyledElement)
+            return anchor;
+        throw new InvalidOperationException("Cannot find a StyledElement to get a TemplatedParent.");
+    }
+
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        if (source is StyledElement newElement)
+        {
+            newElement.PropertyChanged += OnPropertyChanged;
+            SetValue(newElement.TemplatedParent);
+        }
+        else
+        {
+            SetError($"Unable to read TemplatedParent from '{source.GetType()}'.");
+        }
+    }
+
+    protected override void Unsubscribe(object oldSource)
+    {
+        if (oldSource is StyledElement oldElement)
+            oldElement.PropertyChanged -= OnPropertyChanged;
+    }
+
+    private void OnPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+    {
+        if (sender == Source && e.Property == StyledElement.TemplatedParentProperty)
+            SetValue(e.NewValue);
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNodes/VisualAncestorElementNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNodes/VisualAncestorElementNode.cs
new file mode 100644
index 000000000..4bca2c8cb
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/ExpressionNodes/VisualAncestorElementNode.cs
@@ -0,0 +1,86 @@
+using System;
+using System.Text;
+using Avalonia.Reactive;
+using Avalonia.VisualTree;
+
+namespace Avalonia.Data.Core.ExpressionNodes;
+
+internal sealed class VisualAncestorElementNode : SourceNode
+{
+    private readonly Type? _ancestorType;
+    private readonly int _ancestorLevel;
+    private IDisposable? _subscription;
+
+    public VisualAncestorElementNode(Type? ancestorType, int ancestorLevel)
+    {
+        _ancestorType = ancestorType;
+        _ancestorLevel = ancestorLevel;
+    }
+
+    public override void BuildString(StringBuilder builder)
+    {
+        builder.Append("$visualParent");
+
+        if (_ancestorLevel > 0 || _ancestorType is not null)
+        {
+            builder.Append('[');
+
+            if (_ancestorType is not null)
+            {
+                builder.Append(_ancestorType.Name);
+                if (_ancestorLevel > 0)
+                    builder.Append(',');
+            }
+
+            if (_ancestorLevel > 0)
+                builder.Append(_ancestorLevel);
+
+            builder.Append(']');
+        }
+    }
+
+    public override object? SelectSource(object? source, object target, object? anchor)
+    {
+        if (source != AvaloniaProperty.UnsetValue)
+            throw new NotSupportedException(
+                "VisualAncestorNode is invalid in conjunction with a binding source.");
+        if (target is Visual)
+            return target;
+        if (anchor is Visual)
+            return anchor;
+        throw new InvalidOperationException("Cannot find an ILogical to get a visual ancestor.");
+    }
+
+    public override bool ShouldLogErrors(object target)
+    {
+        return target is Visual visual && visual.IsAttachedToVisualTree;
+    }
+
+    protected override void OnSourceChanged(object source, Exception? dataValidationError)
+    {
+        if (source is Visual visual)
+        {
+            var locator = VisualLocator.Track(visual, _ancestorLevel, _ancestorType);
+            _subscription = locator.Subscribe(TrackedControlChanged);
+        }
+    }
+
+    protected override void Unsubscribe(object oldSource)
+    {
+        _subscription?.Dispose();
+        _subscription = null;
+    }
+
+
+    private void TrackedControlChanged(Visual? control)
+    {
+        if (control is not null)
+        {
+            SetValue(control);
+        }
+        else
+        {
+            SetError("Ancestor not found.");
+        }
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/ExpressionObserver.cs b/src/Avalonia.Base/Data/Core/ExpressionObserver.cs
deleted file mode 100644
index a4658e643..000000000
--- a/src/Avalonia.Base/Data/Core/ExpressionObserver.cs
+++ /dev/null
@@ -1,316 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
-using System.Linq.Expressions;
-using Avalonia.Data.Core.Parsers;
-using Avalonia.Data.Core.Plugins;
-using Avalonia.Reactive;
-
-namespace Avalonia.Data.Core
-{
-    /// <summary>
-    /// Observes and sets the value of an expression on an object.
-    /// </summary>
-    internal class ExpressionObserver : LightweightObservableBase<object?>, IDescription
-    {
-        /// <summary>
-        /// An ordered collection of property accessor plugins that can be used to customize
-        /// the reading and subscription of property values on a type.
-        /// </summary>
-        public static readonly List<IPropertyAccessorPlugin> PropertyAccessors =
-            new List<IPropertyAccessorPlugin>
-            {
-                new AvaloniaPropertyAccessorPlugin(),
-                new MethodAccessorPlugin(),
-                new InpcPropertyAccessorPlugin(),
-            };
-
-        /// <summary>
-        /// An ordered collection of validation checker plugins that can be used to customize
-        /// the validation of view model and model data.
-        /// </summary>
-        public static readonly List<IDataValidationPlugin> DataValidators =
-            new List<IDataValidationPlugin>
-            {
-                new DataAnnotationsValidationPlugin(),
-                new IndeiValidationPlugin(),
-                new ExceptionValidationPlugin(),
-            };
-
-        /// <summary>
-        /// An ordered collection of stream plugins that can be used to customize the behavior
-        /// of the '^' stream binding operator.
-        /// </summary>
-        public static readonly List<IStreamPlugin> StreamHandlers =
-            new List<IStreamPlugin>
-            {
-                new TaskStreamPlugin(),
-                new ObservableStreamPlugin(),
-            };
-        private readonly ExpressionNode _node;
-        private readonly object? _root;
-        private readonly Func<object?>? _rootGetter;
-        private IDisposable? _rootSubscription;
-        private WeakReference<object?>? _value;
-        private IReadOnlyList<ITransformNode>? _transformNodes;
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ExpressionObserver"/> class.
-        /// </summary>
-        /// <param name="root">The root object.</param>
-        /// <param name="node">The expression.</param>
-        /// <param name="description">
-        /// A description of the expression.
-        /// </param>
-        public ExpressionObserver(
-            object? root,
-            ExpressionNode node,
-            string? description = null)
-        {
-            _node = node;
-            Description = description;
-            _root = new WeakReference<object?>(root == AvaloniaProperty.UnsetValue ? null : root);
-        }
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ExpressionObserver"/> class.
-        /// </summary>
-        /// <param name="rootObservable">An observable which provides the root object.</param>
-        /// <param name="node">The expression.</param>
-        /// <param name="description">
-        /// A description of the expression.
-        /// </param>
-        public ExpressionObserver(
-            IObservable<object?> rootObservable,
-            ExpressionNode node,
-            string? description)
-        {
-            _ = rootObservable ??throw new ArgumentNullException(nameof(rootObservable));
-            
-            _node = node;
-            Description = description;
-            _root = rootObservable;
-        }
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ExpressionObserver"/> class.
-        /// </summary>
-        /// <param name="rootGetter">A function which gets the root object.</param>
-        /// <param name="node">The expression.</param>
-        /// <param name="update">An observable which triggers a re-read of the getter. Generic argument value is not used.</param>
-        /// <param name="description">
-        /// A description of the expression.
-        /// </param>
-        public ExpressionObserver(
-            Func<object?> rootGetter,
-            ExpressionNode node,
-            IObservable<ValueTuple> update,
-            string? description)
-        {
-            Description = description;
-            _rootGetter = rootGetter ?? throw new ArgumentNullException(nameof(rootGetter));
-            _node = node ?? throw new ArgumentNullException(nameof(node));
-            _root = update.Select(x => rootGetter());
-        }
-
-
-        /// <summary>
-        /// Creates a new instance of the <see cref="ExpressionObserver"/> class.
-        /// </summary>
-        /// <param name="root">The root object.</param>
-        /// <param name="expression">The expression.</param>
-        /// <param name="enableDataValidation">Whether or not to track data validation</param>
-        /// <param name="description">
-        /// A description of the expression. If null, <paramref name="expression"/>'s string representation will be used.
-        /// </param>
-        [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = TrimmingMessages.ExpressionSafeSupressWarningMessage)]
-        public static ExpressionObserver Create<T, U>(
-            T? root,
-            Expression<Func<T, U>> expression,
-            bool enableDataValidation = false,
-            string? description = null)
-        {
-            return new ExpressionObserver(root, Parse(expression, enableDataValidation), description ?? expression.ToString());
-        }
-
-        /// <summary>
-        /// Creates a new instance of the <see cref="ExpressionObserver"/> class.
-        /// </summary>
-        /// <param name="rootObservable">An observable which provides the root object.</param>
-        /// <param name="expression">The expression.</param>
-        /// <param name="enableDataValidation">Whether or not to track data validation</param>
-        /// <param name="description">
-        /// A description of the expression. If null, <paramref name="expression"/>'s string representation will be used.
-        /// </param>
-        [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = TrimmingMessages.ExpressionSafeSupressWarningMessage)]
-        public static ExpressionObserver Create<T, U>(
-            IObservable<T> rootObservable,
-            Expression<Func<T, U>> expression,
-            bool enableDataValidation = false,
-            string? description = null)
-        {
-            _ = rootObservable ?? throw new ArgumentNullException(nameof(rootObservable));
-
-            return new ExpressionObserver(
-                rootObservable.Select(o => (object?)o),
-                Parse(expression, enableDataValidation),
-                description ?? expression.ToString());
-        }
-
-        /// <summary>
-        /// Creates a new instance of the <see cref="ExpressionObserver"/> class.
-        /// </summary>
-        /// <param name="rootGetter">A function which gets the root object.</param>
-        /// <param name="expression">The expression.</param>
-        /// <param name="update">An observable which triggers a re-read of the getter. Generic argument value is not used.</param>
-        /// <param name="enableDataValidation">Whether or not to track data validation</param>
-        /// <param name="description">
-        /// A description of the expression. If null, <paramref name="expression"/>'s string representation will be used.
-        /// </param>
-        [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = TrimmingMessages.ExpressionSafeSupressWarningMessage)]
-        public static ExpressionObserver Create<T, U>(
-            Func<T> rootGetter,
-            Expression<Func<T, U>> expression,
-            IObservable<ValueTuple> update,
-            bool enableDataValidation = false,
-            string? description = null)
-        {
-            _ = rootGetter ?? throw new ArgumentNullException(nameof(rootGetter));
-
-            return new ExpressionObserver(
-                () => rootGetter(),
-                Parse(expression, enableDataValidation),
-                update,
-                description ?? expression.ToString());
-        }
-
-        private IReadOnlyList<ITransformNode> GetTransformNodesFromChain()
-        {
-            LinkedList<ITransformNode> transforms = new LinkedList<ITransformNode>();
-            var node = _node;
-            while (node != null)
-            {
-                if (node is ITransformNode transform)
-                {
-                    transforms.AddFirst(transform);
-                }
-                node = node.Next;
-            }
-
-            return new List<ITransformNode>(transforms);
-        }
-
-        private IReadOnlyList<ITransformNode> TransformNodes => (_transformNodes ?? (_transformNodes = GetTransformNodesFromChain()));
-
-        /// <summary>
-        /// Attempts to set the value of a property expression.
-        /// </summary>
-        /// <param name="value">The value to set.</param>
-        /// <param name="priority">The binding priority to use.</param>
-        /// <returns>
-        /// True if the value could be set; false if the expression does not evaluate to a 
-        /// property. Note that the <see cref="ExpressionObserver"/> must be subscribed to
-        /// before setting the target value can work, as setting the value requires the
-        /// expression to be evaluated.
-        /// </returns>
-        public bool SetValue(object? value, BindingPriority priority = BindingPriority.LocalValue)
-        {
-            if (Leaf is SettableNode settable)
-            {
-                foreach (var transform in TransformNodes)
-                {
-                    value = transform.Transform(value);
-                    if (value is BindingNotification)
-                    {
-                        return false;
-                    }
-                }
-                return settable.SetTargetValue(value, priority);
-            }
-            return false;
-        }
-
-        /// <summary>
-        /// Gets a description of the expression being observed.
-        /// </summary>
-        public string? Description { get; }
-
-        /// <summary>
-        /// Gets the expression being observed.
-        /// </summary>
-        public string? Expression { get; }
-
-        /// <summary>
-        /// Gets the type of the expression result or null if the expression could not be 
-        /// evaluated.
-        /// </summary>
-        public Type? ResultType => (Leaf as SettableNode)?.PropertyType;
-
-        /// <summary>
-        /// Gets the leaf node.
-        /// </summary>
-        private ExpressionNode Leaf
-        {
-            get
-            {
-                var node = _node;
-                while (node.Next != null) node = node.Next;
-                return node;
-            }
-        }
-
-        protected override void Initialize()
-        {
-            _value = null;
-            if (_rootGetter is not null)
-                _node.Target = new WeakReference<object?>(_rootGetter());
-            _node.Subscribe(ValueChanged);
-            StartRoot();
-        }
-
-        protected override void Deinitialize()
-        {
-            _rootSubscription?.Dispose();
-            _rootSubscription = null;
-            _node.Unsubscribe();
-        }
-
-        protected override void Subscribed(IObserver<object?> observer, bool first)
-        {
-            if (!first && _value != null && _value.TryGetTarget(out var value))
-            {
-                observer.OnNext(value);
-            }
-        }
-
-        [RequiresUnreferencedCode(TrimmingMessages.ExpressionNodeRequiresUnreferencedCodeMessage)]
-        private static ExpressionNode Parse(LambdaExpression expression, bool enableDataValidation)
-        {
-            return ExpressionTreeParser.Parse(expression, enableDataValidation);
-        }
-
-        private void StartRoot()
-        {
-            if (_root is IObservable<object> observable)
-            {
-                _rootSubscription = observable.Subscribe(
-                    new AnonymousObserver<object>(
-                        x => _node.Target = new WeakReference<object?>(x != AvaloniaProperty.UnsetValue ? x : null),
-                        x => PublishCompleted(),
-                        PublishCompleted));
-            }
-            else
-            {
-                _node.Target = (WeakReference<object?>)_root!;
-            }
-        }
-
-        private void ValueChanged(object? value)
-        {
-            var broken = BindingNotification.ExtractError(value) as MarkupBindingChainException;
-            broken?.Commit(Description ?? "{empty}");
-            _value = new WeakReference<object?>(value);
-            PublishNext(value);
-        }
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/IBinding2.cs b/src/Avalonia.Base/Data/Core/IBinding2.cs
new file mode 100644
index 000000000..5e57bedd0
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/IBinding2.cs
@@ -0,0 +1,20 @@
+namespace Avalonia.Data.Core;
+
+/// <summary>
+/// Internal interface for instancing bindings on an <see cref="AvaloniaObject"/>.
+/// </summary>
+/// <remarks>
+/// TODO12: The presence of this interface is a hack needed because we can't break our API until
+/// 12.0. The Instance method would ideally be located as an internal method on a BindingBase
+/// class, but we already have a BindingBase in 11.x which is not suitable for this as it contains
+/// extra members that are not needed on all of the binding types. The current BindingBase should
+/// be renamed to something like BindingMarkupExtensionBase and a new BindingBase created with the
+/// Instance method from this interface. This interface should then be removed.
+/// </remarks>
+internal interface IBinding2 : IBinding
+{
+    BindingExpressionBase Instance(
+        AvaloniaObject target,
+        AvaloniaProperty targetProperty,
+        object? anchor);
+}
diff --git a/src/Avalonia.Base/Data/Core/IBindingExpressionSink.cs b/src/Avalonia.Base/Data/Core/IBindingExpressionSink.cs
new file mode 100644
index 000000000..a068536e1
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/IBindingExpressionSink.cs
@@ -0,0 +1,34 @@
+namespace Avalonia.Data.Core;
+
+internal interface IBindingExpressionSink
+{
+    /// <summary>
+    /// Called when an <see cref="UntypedBindingExpressionBase"/>'s value or error state
+    /// changes.
+    /// </summary>
+    /// <param name="instance">The binding expression.</param>
+    /// <param name="hasValueChanged">
+    /// Indicates whether <paramref name="value"/> represents a new value produced by the binding.
+    /// </param>
+    /// <param name="hasErrorChanged">
+    /// Indicates whether <paramref name="error"/> represents a new error produced by the binding.
+    /// </param>
+    /// <param name="value">
+    /// The new binding value; if <paramref name="hasValueChanged"/> is true.
+    /// </param>
+    /// <param name="error">
+    /// The new binding error; if <paramref name="hasErrorChanged"/> is true.
+    /// </param>
+    void OnChanged(
+        UntypedBindingExpressionBase instance,
+        bool hasValueChanged,
+        bool hasErrorChanged,
+        object? value,
+        BindingError? error);
+
+    /// <summary>
+    /// Called when an <see cref="UntypedBindingExpressionBase"/> completes.
+    /// </summary>
+    /// <param name="instance">The binding expression.</param>
+    void OnCompleted(UntypedBindingExpressionBase instance);
+}
diff --git a/src/Avalonia.Base/Data/Core/ITransformNode.cs b/src/Avalonia.Base/Data/Core/ITransformNode.cs
deleted file mode 100644
index 645d637e4..000000000
--- a/src/Avalonia.Base/Data/Core/ITransformNode.cs
+++ /dev/null
@@ -1,7 +0,0 @@
-namespace Avalonia.Data.Core
-{
-    interface ITransformNode
-    {
-        object? Transform(object? value);
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/IndexerBindingExpression.cs b/src/Avalonia.Base/Data/Core/IndexerBindingExpression.cs
new file mode 100644
index 000000000..0a92e4b6a
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/IndexerBindingExpression.cs
@@ -0,0 +1,68 @@
+using System;
+
+namespace Avalonia.Data.Core;
+
+internal class IndexerBindingExpression : UntypedBindingExpressionBase
+{
+    private readonly AvaloniaObject _source;
+    private readonly AvaloniaProperty _sourceProperty;
+    private readonly AvaloniaObject _target;
+    private readonly AvaloniaProperty? _targetProperty;
+    private readonly BindingMode _mode;
+
+    public IndexerBindingExpression(
+        AvaloniaObject source,
+        AvaloniaProperty sourceProperty,
+        AvaloniaObject target,
+        AvaloniaProperty? targetProperty,
+        BindingMode mode)
+        : base(BindingPriority.LocalValue)
+    {
+        _source = source;
+        _sourceProperty = sourceProperty;
+        _target = target;
+        _targetProperty = targetProperty;
+        _mode = mode;
+    }
+
+    public override string Description => $"IndexerBinding {_sourceProperty})";
+
+    internal override bool WriteValueToSource(object? value)
+    {
+        _source.SetValue(_sourceProperty, value);
+        return true;
+    }
+
+    protected override void StartCore()
+    {
+        if (_mode is BindingMode.TwoWay or BindingMode.OneWayToSource && _targetProperty is not null)
+            _target.PropertyChanged += OnTargetPropertyChanged;
+
+        if (_mode is not BindingMode.OneWayToSource)
+        {
+            _source.PropertyChanged += OnSourcePropertyChanged;
+            PublishValue(_source.GetValue(_sourceProperty));
+        }
+
+        if (_mode is BindingMode.OneTime)
+            Stop();
+    }
+
+    protected override void StopCore()
+    {
+        _source.PropertyChanged -= OnSourcePropertyChanged;
+        _target.PropertyChanged -= OnTargetPropertyChanged;
+    }
+
+    private void OnSourcePropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+    {
+        if (e.Property == _sourceProperty)
+            PublishValue(_source.GetValue(_sourceProperty));
+    }
+
+    private void OnTargetPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+    {
+        if (e.Property == _targetProperty)
+            WriteValueToSource(e.NewValue);
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/IndexerExpressionNode.cs b/src/Avalonia.Base/Data/Core/IndexerExpressionNode.cs
deleted file mode 100644
index 7a24f9cb7..000000000
--- a/src/Avalonia.Base/Data/Core/IndexerExpressionNode.cs
+++ /dev/null
@@ -1,76 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.ComponentModel;
-using System.Linq.Expressions;
-using System.Reflection;
-
-namespace Avalonia.Data.Core
-{
-    class IndexerExpressionNode : IndexerNodeBase
-    {
-        private readonly ParameterExpression _parameter;
-        private readonly IndexExpression _expression;
-        private readonly Delegate _setDelegate;
-        private readonly Delegate _getDelegate;
-        private readonly Delegate _firstArgumentDelegate;
-
-        public IndexerExpressionNode(IndexExpression expression)
-        {
-            _parameter = Expression.Parameter(expression.Object!.Type);
-            _expression = expression.Update(_parameter, expression.Arguments);
-
-            _getDelegate = Expression.Lambda(_expression, _parameter).Compile();
-
-            var valueParameter = Expression.Parameter(expression.Type);
-
-            _setDelegate = Expression.Lambda(Expression.Assign(_expression, valueParameter), _parameter, valueParameter).Compile();
-
-            _firstArgumentDelegate = Expression.Lambda(_expression.Arguments[0], _parameter).Compile();
-        }
-
-        public override Type PropertyType => _expression.Type;
-
-        public override string Description => _expression.ToString();
-
-        protected override bool SetTargetValueCore(object? value, BindingPriority priority)
-        {
-            try
-            {
-                Target.TryGetTarget(out var target);
-
-                _setDelegate.DynamicInvoke(target, value);
-                return true;
-            }
-            catch (Exception)
-            {
-                return false;
-            }
-        }
-
-        protected override object? GetValue(object? target)
-        {
-            try
-            {
-                return _getDelegate.DynamicInvoke(target);
-            }
-            catch (TargetInvocationException e) when (e.InnerException is ArgumentOutOfRangeException
-                                                        || e.InnerException is IndexOutOfRangeException
-                                                        || e.InnerException is KeyNotFoundException)
-            {
-                return AvaloniaProperty.UnsetValue;
-            }
-        }
-
-        protected override bool ShouldUpdate(object? sender, PropertyChangedEventArgs e)
-        {
-            return _expression.Indexer == null || _expression.Indexer.Name == e.PropertyName;
-        }
-
-        protected override int? TryGetFirstArgumentAsInt()
-        {
-            Target.TryGetTarget(out var target);
-
-            return _firstArgumentDelegate.DynamicInvoke(target) as int?;
-        } 
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/IndexerNodeBase.cs b/src/Avalonia.Base/Data/Core/IndexerNodeBase.cs
deleted file mode 100644
index 57e4fa4a8..000000000
--- a/src/Avalonia.Base/Data/Core/IndexerNodeBase.cs
+++ /dev/null
@@ -1,102 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Specialized;
-using System.ComponentModel;
-using Avalonia.Reactive;
-using Avalonia.Utilities;
-
-namespace Avalonia.Data.Core
-{
-    internal abstract class IndexerNodeBase : SettableNode,
-        IWeakEventSubscriber<NotifyCollectionChangedEventArgs>,
-        IWeakEventSubscriber<PropertyChangedEventArgs>
-    {
-        protected override void StartListeningCore(WeakReference<object?> reference)
-        {
-            reference.TryGetTarget(out var target);
-
-            if (target is INotifyCollectionChanged incc)
-            {
-                WeakEvents.CollectionChanged.Subscribe(incc, this);
-            }
-
-            if (target is INotifyPropertyChanged inpc)
-            {
-                WeakEvents.ThreadSafePropertyChanged.Subscribe(inpc, this);
-            }
-            
-            ValueChanged(GetValue(target));
-        }
-
-        protected override void StopListeningCore()
-        {
-            if (Target.TryGetTarget(out var target))
-            {
-                if (target is INotifyCollectionChanged incc)
-                {
-                    WeakEvents.CollectionChanged.Unsubscribe(incc, this);
-                }
-
-                if (target is INotifyPropertyChanged inpc)
-                {
-                    WeakEvents.ThreadSafePropertyChanged.Unsubscribe(inpc, this);
-                }
-            }
-        }
-
-        protected abstract object? GetValue(object? target);
-
-        protected abstract int? TryGetFirstArgumentAsInt();
-
-        private bool ShouldUpdate(object? sender, NotifyCollectionChangedEventArgs e)
-        {
-            if (sender is IList)
-            {
-                var index = TryGetFirstArgumentAsInt();
-
-                if (index == null)
-                {
-                    return false;
-                }
-
-                switch (e.Action)
-                {
-                    case NotifyCollectionChangedAction.Add:
-                        return index >= e.NewStartingIndex;
-                    case NotifyCollectionChangedAction.Remove:
-                        return index >= e.OldStartingIndex;
-                    case NotifyCollectionChangedAction.Replace:
-                        return index >= e.NewStartingIndex &&
-                               index < e.NewStartingIndex + e.NewItems!.Count;
-                    case NotifyCollectionChangedAction.Move:
-                        return (index >= e.NewStartingIndex &&
-                                index < e.NewStartingIndex + e.NewItems!.Count) ||
-                               (index >= e.OldStartingIndex &&
-                                index < e.OldStartingIndex + e.OldItems!.Count);
-                    case NotifyCollectionChangedAction.Reset:
-                        return true;
-                }
-            }
-
-            return true; // Implementation defined meaning for the index, so just try to update anyway
-        }
-
-        protected abstract bool ShouldUpdate(object? sender, PropertyChangedEventArgs e);
-
-        void IWeakEventSubscriber<NotifyCollectionChangedEventArgs>.OnEvent(object? sender, WeakEvent ev, NotifyCollectionChangedEventArgs e)
-        {
-            if (ShouldUpdate(sender, e))
-            {
-                ValueChanged(GetValue(sender));
-            }
-        }
-
-        void IWeakEventSubscriber<PropertyChangedEventArgs>.OnEvent(object? sender, WeakEvent ev, PropertyChangedEventArgs e)
-        {
-            if (ShouldUpdate(sender, e))
-            {
-                ValueChanged(GetValue(sender));
-            }
-        }
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/LogicalNotNode.cs b/src/Avalonia.Base/Data/Core/LogicalNotNode.cs
deleted file mode 100644
index 81b07bfe8..000000000
--- a/src/Avalonia.Base/Data/Core/LogicalNotNode.cs
+++ /dev/null
@@ -1,91 +0,0 @@
-using System;
-using System.Globalization;
-
-namespace Avalonia.Data.Core
-{
-    internal class LogicalNotNode : ExpressionNode, ITransformNode
-    {
-        public override string Description => "!";
-
-        protected override void NextValueChanged(object? value)
-        {
-            base.NextValueChanged(Negate(value));
-        }
-
-        private static object Negate(object? value)
-        {
-            var notification = value as BindingNotification;
-            var v = BindingNotification.ExtractValue(value);
-
-            BindingNotification GenerateError(Exception e)
-            {
-                notification ??= new BindingNotification(AvaloniaProperty.UnsetValue);
-                notification.AddError(e, BindingErrorType.Error);
-                notification.ClearValue();
-                return notification;
-            }
-
-            if (v != AvaloniaProperty.UnsetValue)
-            {
-                var s = v as string;
-
-                if (s != null)
-                {
-                    bool result;
-
-                    if (bool.TryParse(s, out result))
-                    {
-                        return !result;
-                    }
-                    else
-                    {
-                        return GenerateError(new InvalidCastException($"Unable to convert '{s}' to bool."));
-                    }
-                }
-                else
-                {
-                    try
-                    {
-                        var boolean = Convert.ToBoolean(v, CultureInfo.InvariantCulture);
-
-                        if (notification is object)
-                        {
-                            notification.SetValue(!boolean);
-                            return notification;
-                        }
-                        else
-                        {
-                            return !boolean;
-                        }
-                    }
-                    catch (InvalidCastException)
-                    {
-                        // The error message here is "Unable to cast object of type 'System.Object'
-                        // to type 'System.IConvertible'" which is kinda useless so provide our own.
-                        return GenerateError(new InvalidCastException($"Unable to convert '{v}' to bool."));
-                    }
-                    catch (Exception e)
-                    {
-                        return GenerateError(e);
-                    }
-                }
-            }
-
-            return notification ?? AvaloniaProperty.UnsetValue;
-        }
-
-        public object? Transform(object? value)
-        {
-            if (value is null)
-                return null;
-
-            var originalType = value.GetType();
-            var negated = Negate(value);
-            if (negated is BindingNotification)
-            {
-                return negated;
-            }
-            return Convert.ChangeType(negated, originalType);
-        }
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/MarkupBindingChainException.cs b/src/Avalonia.Base/Data/Core/MarkupBindingChainException.cs
deleted file mode 100644
index 5d23cecbe..000000000
--- a/src/Avalonia.Base/Data/Core/MarkupBindingChainException.cs
+++ /dev/null
@@ -1,43 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-
-namespace Avalonia.Data.Core
-{
-    internal class MarkupBindingChainException : BindingChainException
-    {
-        private IList<string>? _nodes = new List<string>();
-
-        public MarkupBindingChainException(string message)
-            : base(message)
-        {
-        }
-
-        public MarkupBindingChainException(string message, string node)
-            : base(message)
-        {
-            AddNode(node);
-        }
-
-        public MarkupBindingChainException(string message, string expression, string expressionNullPoint)
-            : base(message, expression, expressionNullPoint)
-        {
-            _nodes = null;
-        }
-
-        public bool HasNodes => _nodes?.Count > 0;
-        public void AddNode(string node) => _nodes?.Add(node);
-
-        public void Commit(string expression)
-        {
-            Expression = expression;
-            ExpressionErrorPoint = _nodes != null ?
-                string.Join(".", _nodes.Reverse())
-                    .Replace(".!", "!")
-                    .Replace(".[", "[")
-                    .Replace(".^", "^") :
-                string.Empty;
-            _nodes = null;
-        }
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/Parsers/BindingExpressionVisitor.cs b/src/Avalonia.Base/Data/Core/Parsers/BindingExpressionVisitor.cs
new file mode 100644
index 000000000..9844ed5ce
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/Parsers/BindingExpressionVisitor.cs
@@ -0,0 +1,232 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+using System.Linq.Expressions;
+using System.Reflection;
+using Avalonia.Data.Core.ExpressionNodes;
+using Avalonia.Data.Core.ExpressionNodes.Reflection;
+
+namespace Avalonia.Data.Core.Parsers;
+
+[RequiresUnreferencedCode(TrimmingMessages.ExpressionNodeRequiresUnreferencedCodeMessage)]
+internal class BindingExpressionVisitor<TIn> : ExpressionVisitor
+{
+    private static readonly PropertyInfo AvaloniaObjectIndexer;
+    private static readonly MethodInfo CreateDelegateMethod;
+    private static readonly string IndexerGetterName = "get_Item";
+    private const string MultiDimensionalArrayGetterMethodName = "Get";
+    private readonly bool _enableDataValidation;
+    private readonly LambdaExpression _rootExpression;
+    private readonly List<ExpressionNode> _nodes = new();
+    private Expression? _head;
+
+    public BindingExpressionVisitor(LambdaExpression expression, bool enableDataValidation)
+    {
+        _rootExpression = expression;
+        _enableDataValidation = enableDataValidation;
+    }
+
+    static BindingExpressionVisitor()
+    {
+        AvaloniaObjectIndexer = typeof(AvaloniaObject).GetProperty("Item", new[] { typeof(AvaloniaProperty) })!;
+        CreateDelegateMethod = typeof(MethodInfo).GetMethod("CreateDelegate", new[] { typeof(Type), typeof(object) })!;
+    }
+
+    public static List<ExpressionNode> BuildNodes<TOut>(Expression<Func<TIn, TOut>> expression, bool enableDataValidation)
+    {
+        var visitor = new BindingExpressionVisitor<TIn>(expression, enableDataValidation);
+        visitor.Visit(expression);
+        return visitor._nodes;
+    }
+
+    protected override Expression VisitBinary(BinaryExpression node)
+    {
+        // Indexers require more work since the compiler doesn't generate IndexExpressions:
+        // they weren't in System.Linq.Expressions v1 and so must be generated manually.
+        if (node.NodeType == ExpressionType.ArrayIndex)
+            return Visit(Expression.MakeIndex(node.Left, null, new[] { node.Right }));
+
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitIndex(IndexExpression node)
+    {
+        if (node.Indexer == AvaloniaObjectIndexer)
+        {
+            var property = GetValue<AvaloniaProperty>(node.Arguments[0]);
+            return Add(node.Object, node, new AvaloniaPropertyAccessorNode(property));
+        }
+        else
+        {
+            return Add(node.Object, node, new ExpressionTreeIndexerNode(node));
+        }
+    }
+
+    protected override Expression VisitMember(MemberExpression node)
+    {
+        switch (node.Member.MemberType)
+        {
+            case MemberTypes.Property:
+                return Add(node.Expression, node, new DynamicPluginPropertyAccessorNode(node.Member.Name));
+            default:
+                throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+        }
+    }
+
+    protected override Expression VisitMethodCall(MethodCallExpression node)
+    {
+        var method = node.Method;
+
+        if (method.Name == IndexerGetterName && node.Object is not null)
+        {
+            var property = TryGetPropertyFromMethod(method);
+            return Visit(Expression.MakeIndex(node.Object, property, node.Arguments));
+        }
+        else if (method.Name == MultiDimensionalArrayGetterMethodName &&
+                 node.Object is not null)
+        {
+            var expression = Expression.MakeIndex(node.Object, null, node.Arguments);
+            return Add(node.Object, node, new ExpressionTreeIndexerNode(expression));
+        }
+        else if (method.Name.StartsWith(StreamBindingExtensions.StreamBindingName) &&
+                 method.DeclaringType == typeof(StreamBindingExtensions))
+        {
+            var instance = node.Method.IsStatic ? node.Arguments[0] : node.Object;
+            Add(instance, node, new DynamicPluginStreamNode());
+            return node;
+        }
+        else if (method == CreateDelegateMethod)
+        {
+            var accessor = new DynamicPluginPropertyAccessorNode(GetValue<MethodInfo>(node.Object!).Name);
+            return Add(node.Arguments[1], node, accessor);
+        }
+
+        throw new ExpressionParseException(0, $"Invalid method call in binding expression: '{node.Method.DeclaringType}.{node.Method.Name}'.");
+    }
+
+    protected override Expression VisitParameter(ParameterExpression node)
+    {
+        if (node == _rootExpression.Parameters[0] && _head is null)
+            _head = node;
+        return base.VisitParameter(node);
+    }
+    
+    protected override Expression VisitUnary(UnaryExpression node)
+    {
+        if (node.NodeType == ExpressionType.Not && node.Type == typeof(bool))
+        {
+            return Add(node.Operand, node, new LogicalNotNode());
+        }
+        else if (node.NodeType == ExpressionType.Convert)
+        {
+            if (node.Operand.Type.IsAssignableFrom(node.Type))
+            {
+                // Ignore inheritance casts 
+                return _head = base.VisitUnary(node);
+            }
+        }
+        else if (node.NodeType == ExpressionType.TypeAs)
+        {
+            // Ignore as operator.
+            return _head = base.VisitUnary(node);
+        }
+
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitBlock(BlockExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override CatchBlock VisitCatchBlock(CatchBlock node)
+    {
+        throw new ExpressionParseException(0, $"Catch blocks are not allowed in binding expressions.");
+    }
+
+    protected override Expression VisitConditional(ConditionalExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitDynamic(DynamicExpression node)
+    {
+        throw new ExpressionParseException(0, $"Dynamic expressions are not allowed in binding expressions.");
+    }
+
+    protected override ElementInit VisitElementInit(ElementInit node)
+    {
+        throw new ExpressionParseException(0, $"Element init expressions are not valid in a binding expression.");
+    }
+
+    protected override Expression VisitGoto(GotoExpression node)
+    {
+        throw new ExpressionParseException(0, $"Goto expressions not supported in binding expressions.");
+    }
+
+    protected override Expression VisitInvocation(InvocationExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitLabel(LabelExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitListInit(ListInitExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitLoop(LoopExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override MemberAssignment VisitMemberAssignment(MemberAssignment node)
+    {
+        throw new ExpressionParseException(0, $"Member assignments not supported in binding expressions.");
+    }
+
+    protected override Expression VisitSwitch(SwitchExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitTry(TryExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitTypeBinary(TypeBinaryExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    private Expression Add(Expression? instance, Expression expression, ExpressionNode node)
+    {
+        var visited = Visit(instance);
+        if (visited != _head)
+            throw new ExpressionParseException(
+                0, 
+                $"Unable to parse '{expression}': expected an instance of '{_head}' but got '{visited}'.");
+        _nodes.Add(node);
+        return _head = expression;
+    }
+
+    private static T GetValue<T>(Expression expr)
+    {
+        if (expr is ConstantExpression constant)
+            return (T)constant.Value!;
+        return Expression.Lambda<Func<T>>(expr).Compile(preferInterpretation: true)();
+    }
+
+    private static PropertyInfo? TryGetPropertyFromMethod(MethodInfo method)
+    {
+        var type = method.DeclaringType;
+        return type?.GetRuntimeProperties().FirstOrDefault(prop => prop.GetMethod == method);
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/Parsers/ExpressionTreeParser.cs b/src/Avalonia.Base/Data/Core/Parsers/ExpressionTreeParser.cs
deleted file mode 100644
index c48be6a17..000000000
--- a/src/Avalonia.Base/Data/Core/Parsers/ExpressionTreeParser.cs
+++ /dev/null
@@ -1,26 +0,0 @@
-using System.Diagnostics.CodeAnalysis;
-using System.Linq;
-using System.Linq.Expressions;
-
-namespace Avalonia.Data.Core.Parsers
-{
-    static class ExpressionTreeParser
-    {
-        [RequiresUnreferencedCode(TrimmingMessages.ExpressionNodeRequiresUnreferencedCodeMessage)]
-        public static ExpressionNode Parse(Expression expr, bool enableDataValidation)
-        {
-            var visitor = new ExpressionVisitorNodeBuilder(enableDataValidation);
-
-            visitor.Visit(expr);
-
-            var nodes = visitor.Nodes;
-
-            for (int n = 0; n < nodes.Count - 1; ++n)
-            {
-                nodes[n].Next = nodes[n + 1];
-            }
-
-            return nodes.FirstOrDefault() ?? new EmptyExpressionNode();
-        }
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/Parsers/ExpressionVisitorNodeBuilder.cs b/src/Avalonia.Base/Data/Core/Parsers/ExpressionVisitorNodeBuilder.cs
deleted file mode 100644
index 7498da3cc..000000000
--- a/src/Avalonia.Base/Data/Core/Parsers/ExpressionVisitorNodeBuilder.cs
+++ /dev/null
@@ -1,219 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
-using System.Linq;
-using System.Linq.Expressions;
-using System.Reflection;
-
-namespace Avalonia.Data.Core.Parsers
-{
-    [RequiresUnreferencedCode(TrimmingMessages.ExpressionNodeRequiresUnreferencedCodeMessage)]
-    class ExpressionVisitorNodeBuilder : ExpressionVisitor
-    {
-        private const string MultiDimensionalArrayGetterMethodName = "Get";
-        private static readonly PropertyInfo AvaloniaObjectIndexer;
-        private static readonly MethodInfo CreateDelegateMethod;
-
-        private readonly bool _enableDataValidation;
-
-        static ExpressionVisitorNodeBuilder()
-        {
-            AvaloniaObjectIndexer = typeof(AvaloniaObject).GetProperty("Item", new[] { typeof(AvaloniaProperty) })!;
-            CreateDelegateMethod = typeof(MethodInfo).GetMethod("CreateDelegate", new[] { typeof(Type), typeof(object) })!;
-        }
-
-        public List<ExpressionNode> Nodes { get; }
-
-        public ExpressionVisitorNodeBuilder(bool enableDataValidation)
-        {
-            _enableDataValidation = enableDataValidation;
-            Nodes = new List<ExpressionNode>();
-        }
-
-        protected override Expression VisitUnary(UnaryExpression node)
-        {
-            if (node.NodeType == ExpressionType.Not && node.Type == typeof(bool))
-            {
-                Nodes.Add(new LogicalNotNode());
-            }
-            else if (node.NodeType == ExpressionType.Convert)
-            {
-                if (node.Operand.Type.IsAssignableFrom(node.Type))
-                {
-                    // Ignore inheritance casts 
-                }
-                else
-                {
-                    throw new ExpressionParseException(0, $"Cannot parse non-inheritance casts in a binding expression.");
-                }
-            }
-            else if (node.NodeType == ExpressionType.TypeAs)
-            {
-                // Ignore as operator.
-            }
-            else
-            {
-                throw new ExpressionParseException(0, $"Unable to parse unary operator {node.NodeType} in a binding expression");
-            }
-
-            return base.VisitUnary(node);
-        }
-
-        protected override Expression VisitMember(MemberExpression node)
-        {
-            var visited = base.VisitMember(node);
-            Nodes.Add(new PropertyAccessorNode(node.Member.Name, _enableDataValidation));
-            return visited;
-        }
-
-        protected override Expression VisitIndex(IndexExpression node)
-        {
-            Visit(node.Object);
-
-            if (node.Indexer == AvaloniaObjectIndexer)
-            {
-                var property = GetArgumentExpressionValue<AvaloniaProperty>(node.Arguments[0]);
-                Nodes.Add(new AvaloniaPropertyAccessorNode(property, _enableDataValidation));
-            }
-            else
-            {
-                Nodes.Add(new IndexerExpressionNode(node));
-            }
-
-            return node;
-        }
-
-        private static T GetArgumentExpressionValue<T>(Expression expr)
-        {
-            try
-            {
-                return Expression.Lambda<Func<T>>(expr).Compile(preferInterpretation: true)();
-            }
-            catch (InvalidOperationException ex)
-            {
-                throw new ExpressionParseException(0, "Unable to parse indexer value.", ex);
-            }
-        }
-
-        protected override Expression VisitBinary(BinaryExpression node)
-        {
-            if (node.NodeType == ExpressionType.ArrayIndex)
-            {
-                return Visit(Expression.MakeIndex(node.Left, null, new[] { node.Right }));
-            }
-            throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
-        }
-
-        protected override Expression VisitBlock(BlockExpression node)
-        {
-            throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
-        }
-
-        protected override CatchBlock VisitCatchBlock(CatchBlock node)
-        {
-            throw new ExpressionParseException(0, $"Catch blocks are not allowed in binding expressions.");
-        }
-
-        protected override Expression VisitConditional(ConditionalExpression node)
-        {
-            throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
-        }
-
-        protected override Expression VisitDynamic(DynamicExpression node)
-        {
-            throw new ExpressionParseException(0, $"Dynamic expressions are not allowed in binding expressions.");
-        }
-
-        protected override ElementInit VisitElementInit(ElementInit node)
-        {
-            throw new ExpressionParseException(0, $"Element init expressions are not valid in a binding expression.");
-        }
-
-        protected override Expression VisitGoto(GotoExpression node)
-        {
-            throw new ExpressionParseException(0, $"Goto expressions not supported in binding expressions.");
-        }
-
-        protected override Expression VisitInvocation(InvocationExpression node)
-        {
-            throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
-        }
-
-        protected override Expression VisitLabel(LabelExpression node)
-        {
-            throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
-        }
-
-        protected override Expression VisitListInit(ListInitExpression node)
-        {
-            throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
-        }
-
-        protected override Expression VisitLoop(LoopExpression node)
-        {
-            throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
-        }
-
-        protected override MemberAssignment VisitMemberAssignment(MemberAssignment node)
-        {
-            throw new ExpressionParseException(0, $"Member assignments not supported in binding expressions.");
-        }
-
-        protected override Expression VisitMethodCall(MethodCallExpression node)
-        {
-            if (node.Method == CreateDelegateMethod)
-            {
-                var visited = Visit(node.Arguments[1]);
-                Nodes.Add(new PropertyAccessorNode(GetArgumentExpressionValue<MethodInfo>(node.Object!).Name, _enableDataValidation));
-                return node;
-            }
-            else if (node.Method.Name == StreamBindingExtensions.StreamBindingName || node.Method.Name.StartsWith(StreamBindingExtensions.StreamBindingName + '`'))
-            {
-                if (node.Method.IsStatic)
-                {
-                    Visit(node.Arguments[0]);
-                }
-                else
-                {
-                    Visit(node.Object);
-                }
-                Nodes.Add(new StreamNode());
-                return node;
-            }
-
-            var property = TryGetPropertyFromMethod(node.Method);
-
-            if (property != null)
-            {
-                return Visit(Expression.MakeIndex(node.Object!, property, node.Arguments));
-            }
-            else if (node.Object!.Type.IsArray && node.Method.Name == MultiDimensionalArrayGetterMethodName)
-            {
-                return Visit(Expression.MakeIndex(node.Object, null, node.Arguments));
-            }
-
-            throw new ExpressionParseException(0, $"Invalid method call in binding expression: '{node.Method.DeclaringType!.AssemblyQualifiedName}.{node.Method.Name}'.");
-        }
-
-        private static PropertyInfo? TryGetPropertyFromMethod(MethodInfo method)
-        {
-            var type = method.DeclaringType;
-            return type?.GetRuntimeProperties().FirstOrDefault(prop => prop.GetMethod == method);
-        }
-
-        protected override Expression VisitSwitch(SwitchExpression node)
-        {
-            throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
-        }
-
-        protected override Expression VisitTry(TryExpression node)
-        {
-            throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
-        }
-
-        protected override Expression VisitTypeBinary(TypeBinaryExpression node)
-        {
-            throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
-        }
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/Plugins/AvaloniaPropertyAccessorPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/AvaloniaPropertyAccessorPlugin.cs
index f111d8917..eebe9a3ec 100644
--- a/src/Avalonia.Base/Data/Core/Plugins/AvaloniaPropertyAccessorPlugin.cs
+++ b/src/Avalonia.Base/Data/Core/Plugins/AvaloniaPropertyAccessorPlugin.cs
@@ -1,6 +1,4 @@
 using System;
-using System.Diagnostics.CodeAnalysis;
-using System.Runtime.ExceptionServices;
 using Avalonia.Utilities;
 
 namespace Avalonia.Data.Core.Plugins
@@ -11,7 +9,6 @@ namespace Avalonia.Data.Core.Plugins
     internal class AvaloniaPropertyAccessorPlugin : IPropertyAccessorPlugin
     {
         /// <inheritdoc/>
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
         public bool Match(object obj, string propertyName)
         {
             if (obj is AvaloniaObject o)
@@ -31,7 +28,6 @@ namespace Avalonia.Data.Core.Plugins
         /// An <see cref="IPropertyAccessor"/> interface through which future interactions with the 
         /// property will be made.
         /// </returns>
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
         public IPropertyAccessor? Start(WeakReference<object?> reference, string propertyName)
         {
             _ = reference ?? throw new ArgumentNullException(nameof(reference));
diff --git a/src/Avalonia.Base/Data/Core/Plugins/BindingPlugins.cs b/src/Avalonia.Base/Data/Core/Plugins/BindingPlugins.cs
index 6d88d5577..6164d8ec3 100644
--- a/src/Avalonia.Base/Data/Core/Plugins/BindingPlugins.cs
+++ b/src/Avalonia.Base/Data/Core/Plugins/BindingPlugins.cs
@@ -1,28 +1,50 @@
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 
 namespace Avalonia.Data.Core.Plugins
 {
     /// <summary>
     /// Holds a registry of plugins used for bindings.
     /// </summary>
+    [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
     public static class BindingPlugins
     {
+        internal static readonly List<IPropertyAccessorPlugin> s_propertyAccessors = new()
+        {
+            new AvaloniaPropertyAccessorPlugin(),
+            new ReflectionMethodAccessorPlugin(),
+            new InpcPropertyAccessorPlugin(),
+        };
+
+        internal static readonly List<IDataValidationPlugin> s_dataValidators = new()
+        {
+            new DataAnnotationsValidationPlugin(),
+            new IndeiValidationPlugin(),
+            new ExceptionValidationPlugin(),
+        };
+
+        internal static readonly List<IStreamPlugin> s_streamHandlers = new()
+        {
+            new TaskStreamPlugin(),
+            new ObservableStreamPlugin(),
+        };
+
         /// <summary>
         /// An ordered collection of property accessor plugins that can be used to customize
         /// the reading and subscription of property values on a type.
         /// </summary>
-        public static IList<IPropertyAccessorPlugin> PropertyAccessors => ExpressionObserver.PropertyAccessors;
+        public static IList<IPropertyAccessorPlugin> PropertyAccessors => s_propertyAccessors;
 
         /// <summary>
         /// An ordered collection of validation checker plugins that can be used to customize
         /// the validation of view model and model data.
         /// </summary>
-        public static IList<IDataValidationPlugin> DataValidators => ExpressionObserver.DataValidators;
+        public static IList<IDataValidationPlugin> DataValidators => s_dataValidators;
 
         /// <summary>
         /// An ordered collection of stream plugins that can be used to customize the behavior
         /// of the '^' stream binding operator.
         /// </summary>
-        public static IList<IStreamPlugin> StreamHandlers => ExpressionObserver.StreamHandlers;
+        public static IList<IStreamPlugin> StreamHandlers => s_streamHandlers;
     }
 }
diff --git a/src/Avalonia.Base/Data/Core/Plugins/DataAnnotationsValidationPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/DataAnnotationsValidationPlugin.cs
index bc300386b..bd166d8d9 100644
--- a/src/Avalonia.Base/Data/Core/Plugins/DataAnnotationsValidationPlugin.cs
+++ b/src/Avalonia.Base/Data/Core/Plugins/DataAnnotationsValidationPlugin.cs
@@ -10,10 +10,10 @@ namespace Avalonia.Data.Core.Plugins
     /// <summary>
     /// Validates properties on that have <see cref="ValidationAttribute"/>s.
     /// </summary>
+    [RequiresUnreferencedCode(TrimmingMessages.DataValidationPluginRequiresUnreferencedCodeMessage)]
     public class DataAnnotationsValidationPlugin : IDataValidationPlugin
     {
         /// <inheritdoc/>
-        [RequiresUnreferencedCode(TrimmingMessages.DataValidationPluginRequiresUnreferencedCodeMessage)]
         public bool Match(WeakReference<object?> reference, string memberName)
         {
             reference.TryGetTarget(out var target);
@@ -26,7 +26,6 @@ namespace Avalonia.Data.Core.Plugins
         }
 
         /// <inheritdoc/>
-        [RequiresUnreferencedCode(TrimmingMessages.DataValidationPluginRequiresUnreferencedCodeMessage)]
         public IPropertyAccessor Start(WeakReference<object?> reference, string name, IPropertyAccessor inner)
         {
             return new Accessor(reference, name, inner);
diff --git a/src/Avalonia.Base/Data/Core/Plugins/ExceptionValidationPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/ExceptionValidationPlugin.cs
index 2bb8da2c7..899b542f8 100644
--- a/src/Avalonia.Base/Data/Core/Plugins/ExceptionValidationPlugin.cs
+++ b/src/Avalonia.Base/Data/Core/Plugins/ExceptionValidationPlugin.cs
@@ -10,11 +10,9 @@ namespace Avalonia.Data.Core.Plugins
     public class ExceptionValidationPlugin : IDataValidationPlugin
     {
         /// <inheritdoc/>
-        [RequiresUnreferencedCode(TrimmingMessages.DataValidationPluginRequiresUnreferencedCodeMessage)]
         public bool Match(WeakReference<object?> reference, string memberName) => true;
 
         /// <inheritdoc/>
-        [RequiresUnreferencedCode(TrimmingMessages.DataValidationPluginRequiresUnreferencedCodeMessage)]
         public IPropertyAccessor Start(WeakReference<object?> reference, string name, IPropertyAccessor inner)
         {
             return new Validator(reference, name, inner);
diff --git a/src/Avalonia.Base/Data/Core/Plugins/IDataValidationPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/IDataValidationPlugin.cs
index 5b4d7cd3a..5d2f06d2c 100644
--- a/src/Avalonia.Base/Data/Core/Plugins/IDataValidationPlugin.cs
+++ b/src/Avalonia.Base/Data/Core/Plugins/IDataValidationPlugin.cs
@@ -1,10 +1,9 @@
 using System;
-using System.Diagnostics.CodeAnalysis;
 
 namespace Avalonia.Data.Core.Plugins
 {
     /// <summary>
-    /// Defines how data validation is observed by an <see cref="ExpressionObserver"/>.
+    /// Defines how data validation is observed by an <see cref="BindingExpression"/>.
     /// </summary>
     public interface IDataValidationPlugin
     {
@@ -14,7 +13,6 @@ namespace Avalonia.Data.Core.Plugins
         /// <param name="reference">A weak reference to the object.</param>
         /// <param name="memberName">The name of the member to validate.</param>
         /// <returns>True if the plugin can handle the object; otherwise false.</returns>
-        [RequiresUnreferencedCode(TrimmingMessages.DataValidationPluginRequiresUnreferencedCodeMessage)]
         bool Match(WeakReference<object?> reference, string memberName);
 
         /// <summary>
@@ -27,7 +25,6 @@ namespace Avalonia.Data.Core.Plugins
         /// An <see cref="IPropertyAccessor"/> interface through which future interactions with the 
         /// property will be made.
         /// </returns>
-        [RequiresUnreferencedCode(TrimmingMessages.DataValidationPluginRequiresUnreferencedCodeMessage)]
         IPropertyAccessor Start(WeakReference<object?> reference,
             string propertyName,
             IPropertyAccessor inner);
diff --git a/src/Avalonia.Base/Data/Core/Plugins/IPropertyAccessorPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/IPropertyAccessorPlugin.cs
index 04601bc8b..e2d7312ac 100644
--- a/src/Avalonia.Base/Data/Core/Plugins/IPropertyAccessorPlugin.cs
+++ b/src/Avalonia.Base/Data/Core/Plugins/IPropertyAccessorPlugin.cs
@@ -1,11 +1,9 @@
 using System;
-using System.Diagnostics.CodeAnalysis;
 
 namespace Avalonia.Data.Core.Plugins
 {
     /// <summary>
-    /// Defines how a member is read, written and observed by an
-    /// <see cref="ExpressionObserver"/>.
+    /// Defines how a member is read, written and observed by a binding.
     /// </summary>
     public interface IPropertyAccessorPlugin
     {
@@ -15,7 +13,6 @@ namespace Avalonia.Data.Core.Plugins
         /// <param name="obj">The object.</param>
         /// <param name="propertyName">The property name.</param>
         /// <returns>True if the plugin can handle the property on the object; otherwise false.</returns>
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
         bool Match(object obj, string propertyName);
 
         /// <summary>
@@ -27,7 +24,6 @@ namespace Avalonia.Data.Core.Plugins
         /// An <see cref="IPropertyAccessor"/> interface through which future interactions with the 
         /// property will be made.
         /// </returns>
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
         IPropertyAccessor? Start(WeakReference<object?> reference,
             string propertyName);
     }
diff --git a/src/Avalonia.Base/Data/Core/Plugins/IStreamPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/IStreamPlugin.cs
index 8bf2d6c3d..b741cfaca 100644
--- a/src/Avalonia.Base/Data/Core/Plugins/IStreamPlugin.cs
+++ b/src/Avalonia.Base/Data/Core/Plugins/IStreamPlugin.cs
@@ -1,5 +1,4 @@
 using System;
-using System.Diagnostics.CodeAnalysis;
 
 namespace Avalonia.Data.Core.Plugins
 {
@@ -13,7 +12,6 @@ namespace Avalonia.Data.Core.Plugins
         /// </summary>
         /// <param name="reference">A weak reference to the value.</param>
         /// <returns>True if the plugin can handle the value; otherwise false.</returns>
-        [RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
         bool Match(WeakReference<object?> reference);
 
         /// <summary>
@@ -23,7 +21,6 @@ namespace Avalonia.Data.Core.Plugins
         /// <returns>
         /// An observable that produces the output for the value.
         /// </returns>
-        [RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
         IObservable<object?> Start(WeakReference<object?> reference);
     }
 }
diff --git a/src/Avalonia.Base/Data/Core/Plugins/IndeiValidationPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/IndeiValidationPlugin.cs
index 87a2f67ee..385d96a7b 100644
--- a/src/Avalonia.Base/Data/Core/Plugins/IndeiValidationPlugin.cs
+++ b/src/Avalonia.Base/Data/Core/Plugins/IndeiValidationPlugin.cs
@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
-using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using Avalonia.Utilities;
 
@@ -19,7 +18,6 @@ namespace Avalonia.Data.Core.Plugins
             );
 
         /// <inheritdoc/>
-        [RequiresUnreferencedCode(TrimmingMessages.DataValidationPluginRequiresUnreferencedCodeMessage)]
         public bool Match(WeakReference<object?> reference, string memberName)
         {
             reference.TryGetTarget(out var target);
@@ -28,7 +26,6 @@ namespace Avalonia.Data.Core.Plugins
         }
 
         /// <inheritdoc/>
-        [RequiresUnreferencedCode(TrimmingMessages.DataValidationPluginRequiresUnreferencedCodeMessage)]
         public IPropertyAccessor Start(WeakReference<object?> reference, string name, IPropertyAccessor accessor)
         {
             return new Validator(reference, name, accessor);
diff --git a/src/Avalonia.Base/Data/Core/Plugins/InpcPropertyAccessorPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/InpcPropertyAccessorPlugin.cs
index e8e3e6d50..2f04e7eb9 100644
--- a/src/Avalonia.Base/Data/Core/Plugins/InpcPropertyAccessorPlugin.cs
+++ b/src/Avalonia.Base/Data/Core/Plugins/InpcPropertyAccessorPlugin.cs
@@ -11,13 +11,13 @@ namespace Avalonia.Data.Core.Plugins
     /// Reads a property from a standard C# object that optionally supports the
     /// <see cref="INotifyPropertyChanged"/> interface.
     /// </summary>
+    [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
     internal class InpcPropertyAccessorPlugin : IPropertyAccessorPlugin
     {
         private readonly Dictionary<(Type, string), PropertyInfo?> _propertyLookup =
             new Dictionary<(Type, string), PropertyInfo?>();
 
         /// <inheritdoc/>
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
         public bool Match(object obj, string propertyName) => GetFirstPropertyWithName(obj, propertyName) != null;
 
         /// <summary>
@@ -29,7 +29,6 @@ namespace Avalonia.Data.Core.Plugins
         /// An <see cref="IPropertyAccessor"/> interface through which future interactions with the 
         /// property will be made.
         /// </returns>
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
         public IPropertyAccessor? Start(WeakReference<object?> reference, string propertyName)
         {
             _ = reference ?? throw new ArgumentNullException(nameof(reference));
@@ -55,14 +54,13 @@ namespace Avalonia.Data.Core.Plugins
         private const BindingFlags PropertyBindingFlags =
             BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static | BindingFlags.Instance;
 
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
         private PropertyInfo? GetFirstPropertyWithName(object instance, string propertyName)
         {
             if (instance is IReflectableType reflectableType && instance is not Type)
                 return reflectableType.GetTypeInfo().GetProperty(propertyName, PropertyBindingFlags);
 
             var type = instance.GetType();
-            
+
             var key = (type, propertyName);
 
             if (!_propertyLookup.TryGetValue(key, out var propertyInfo))
@@ -80,7 +78,7 @@ namespace Avalonia.Data.Core.Plugins
 
             var properties = type.GetProperties(PropertyBindingFlags);
 
-            foreach (PropertyInfo propertyInfo in properties)
+            foreach (var propertyInfo in properties)
             {
                 if (propertyInfo.Name == propertyName)
                 {
@@ -95,6 +93,7 @@ namespace Avalonia.Data.Core.Plugins
             return found;
         }
 
+        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
         private class Accessor : PropertyAccessorBase, IWeakEventSubscriber<PropertyChangedEventArgs>
         {
             private readonly WeakReference<object?> _reference;
@@ -117,7 +116,7 @@ namespace Avalonia.Data.Core.Plugins
                 get
                 {
                     var o = GetReferenceTarget();
-                    return (o != null) ? _property.GetValue(o) : null;
+                    return o != null ? _property.GetValue(o) : null;
                 }
             }
 
@@ -125,8 +124,12 @@ namespace Avalonia.Data.Core.Plugins
             {
                 if (_property.CanWrite)
                 {
+                    if (!TypeUtilities.TryConvert(_property.PropertyType, value, null, out var converted))
+                        throw new ArgumentException($"Object of type '{value?.GetType()}' " +
+                            $"cannot be converted to type '{_property.PropertyType}'.");
+
                     _eventRaised = false;
-                    _property.SetValue(GetReferenceTarget(), value);
+                    _property.SetValue(GetReferenceTarget(), converted);
 
                     if (!_eventRaised)
                     {
@@ -159,7 +162,7 @@ namespace Avalonia.Data.Core.Plugins
             {
                 var inpc = GetReferenceTarget() as INotifyPropertyChanged;
 
-                if (inpc != null) 
+                if (inpc != null)
                     WeakEvents.ThreadSafePropertyChanged.Unsubscribe(inpc, this);
             }
 
@@ -184,7 +187,7 @@ namespace Avalonia.Data.Core.Plugins
             {
                 var inpc = GetReferenceTarget() as INotifyPropertyChanged;
 
-                if (inpc != null) 
+                if (inpc != null)
                     WeakEvents.ThreadSafePropertyChanged.Subscribe(inpc, this);
             }
         }
diff --git a/src/Avalonia.Base/Data/Core/Plugins/MethodAccessorPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/MethodAccessorPlugin.cs
index 8170edd65..d908ffb57 100644
--- a/src/Avalonia.Base/Data/Core/Plugins/MethodAccessorPlugin.cs
+++ b/src/Avalonia.Base/Data/Core/Plugins/MethodAccessorPlugin.cs
@@ -1,142 +1,67 @@
 using System;
-using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
-using System.Linq.Expressions;
+using System.Diagnostics;
 using System.Reflection;
 
-namespace Avalonia.Data.Core.Plugins
+namespace Avalonia.Data.Core.Plugins;
+
+internal class MethodAccessorPlugin : IPropertyAccessorPlugin
 {
-    internal class MethodAccessorPlugin : IPropertyAccessorPlugin
+    private readonly MethodInfo _method;
+    private readonly Type _delegateType;
+
+    public MethodAccessorPlugin(MethodInfo method, Type delegateType)
     {
-        private readonly Dictionary<(Type, string), MethodInfo?> _methodLookup =
-            new Dictionary<(Type, string), MethodInfo?>();
+        _method = method;
+        _delegateType = delegateType;
+    }
 
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
-        public bool Match(object obj, string methodName) => GetFirstMethodWithName(obj.GetType(), methodName) != null;
+    public bool Match(object obj, string propertyName)
+    {
+        throw new InvalidOperationException("The MethodAccessorPlugin does not support dynamic matching");
+    }
 
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
-        public IPropertyAccessor? Start(WeakReference<object?> reference, string methodName)
+    public IPropertyAccessor Start(WeakReference<object?> reference, string propertyName)
+    {
+        Debug.Assert(_method.Name == propertyName);
+        return new Accessor(reference, _method, _delegateType);
+    }
+
+    private sealed class Accessor : PropertyAccessorBase
+    {
+        public Accessor(WeakReference<object?> reference, MethodInfo method, Type delegateType)
         {
             _ = reference ?? throw new ArgumentNullException(nameof(reference));
-            _ = methodName ?? throw new ArgumentNullException(nameof(methodName));
+            _ = method ?? throw new ArgumentNullException(nameof(method));
 
-            if (!reference.TryGetTarget(out var instance) || instance is null)
-                return null;
+            PropertyType = delegateType;
 
-            var method = GetFirstMethodWithName(instance.GetType(), methodName);
-
-            if (method is not null)
+            if (method.IsStatic)
             {
-                return new Accessor(reference, method);
+                Value = method.CreateDelegate(PropertyType);
             }
-            else
+            else if (reference.TryGetTarget(out var target))
             {
-                var message = $"Could not find CLR method '{methodName}' on '{instance}'";
-                var exception = new MissingMemberException(message);
-                return new PropertyError(new BindingNotification(exception, BindingErrorType.Error));
+                Value = method.CreateDelegate(PropertyType, target);
             }
         }
 
-        private MethodInfo? GetFirstMethodWithName(
-            [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods | DynamicallyAccessedMemberTypes.NonPublicMethods)] Type type, string methodName)
+        public override Type? PropertyType { get; }
+
+        public override object? Value { get; }
+
+        public override bool SetValue(object? value, BindingPriority priority) => false;
+
+        protected override void SubscribeCore()
         {
-            var key = (type, methodName);
-
-            if (!_methodLookup.TryGetValue(key, out var methodInfo))
+            try
             {
-                methodInfo = TryFindAndCacheMethod(type, methodName);
+                PublishValue(Value);
             }
-
-            return methodInfo;
+            catch { }
         }
 
-        private MethodInfo? TryFindAndCacheMethod(
-            [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods | DynamicallyAccessedMemberTypes.NonPublicMethods)] Type type, string methodName)
+        protected override void UnsubscribeCore()
         {
-            MethodInfo? found = null;
-
-            const BindingFlags bindingFlags =
-                BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static | BindingFlags.Instance;
-
-            var methods = type.GetMethods(bindingFlags);
-
-            foreach (var methodInfo in methods)
-            {
-                if (methodInfo.Name == methodName)
-                {
-                    var parameters = methodInfo.GetParameters();
-                    if (parameters.Length == 1 && parameters[0].ParameterType == typeof(object))
-                    {
-                        found = methodInfo;
-                        break;
-                    }
-                    else if (parameters.Length == 0)
-                    {
-                        found = methodInfo;
-                    }
-                }
-            }
-
-            _methodLookup.Add((type, methodName), found);
-
-            return found;
-        }
-
-        private sealed class Accessor : PropertyAccessorBase
-        {
-            public Accessor(WeakReference<object?> reference, MethodInfo method)
-            {
-                _ = reference ?? throw new ArgumentNullException(nameof(reference));
-                _ = method ?? throw new ArgumentNullException(nameof(method));
-
-                var returnType = method.ReturnType;
-
-                var parameters = method.GetParameters();
-
-                var signatureTypeCount = parameters.Length + 1;
-
-                var paramTypes = new Type[signatureTypeCount];
-
-
-                for (var i = 0; i < parameters.Length; i++)
-                {
-                    ParameterInfo parameter = parameters[i];
-
-                    paramTypes[i] = parameter.ParameterType;
-                }
-
-                paramTypes[paramTypes.Length - 1] = returnType;
-
-                PropertyType = Expression.GetDelegateType(paramTypes);
-
-                if (method.IsStatic)
-                {
-                    Value = method.CreateDelegate(PropertyType);
-                }
-                else if (reference.TryGetTarget(out var target))
-                {
-                    Value = method.CreateDelegate(PropertyType, target);
-                }
-            }
-
-            public override Type? PropertyType { get; }
-
-            public override object? Value { get; }
-
-            public override bool SetValue(object? value, BindingPriority priority) => false;
-
-            protected override void SubscribeCore()
-            {
-                try
-                {
-                    PublishValue(Value);
-                }
-                catch { }
-            }
-
-            protected override void UnsubscribeCore()
-            {
-            }
         }
     }
 }
diff --git a/src/Avalonia.Base/Data/Core/Plugins/ObservableStreamPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/ObservableStreamPlugin.cs
index 9cf25281f..523c0bcf3 100644
--- a/src/Avalonia.Base/Data/Core/Plugins/ObservableStreamPlugin.cs
+++ b/src/Avalonia.Base/Data/Core/Plugins/ObservableStreamPlugin.cs
@@ -1,8 +1,8 @@
 using System;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
-using Avalonia.Reactive;
 using System.Reflection;
+using Avalonia.Reactive;
 
 namespace Avalonia.Data.Core.Plugins
 {
@@ -10,6 +10,7 @@ namespace Avalonia.Data.Core.Plugins
     /// Handles binding to <see cref="IObservable{T}"/>s for the '^' stream binding operator.
     /// </summary>
     [UnconditionalSuppressMessage("Trimming", "IL3050", Justification = TrimmingMessages.IgnoreNativeAotSupressWarningMessage)]
+    [RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
     internal class ObservableStreamPlugin : IStreamPlugin
     {
         private static MethodInfo? s_observableGeneric;
@@ -18,15 +19,14 @@ namespace Avalonia.Data.Core.Plugins
         [DynamicDependency(DynamicallyAccessedMemberTypes.NonPublicMethods, "Avalonia.Data.Core.Plugins.ObservableStreamPlugin", "Avalonia.Base")]
         public ObservableStreamPlugin()
         {
-            
+
         }
-        
+
         /// <summary>
         /// Checks whether this plugin handles the specified value.
         /// </summary>
         /// <param name="reference">A weak reference to the value.</param>
         /// <returns>True if the plugin can handle the value; otherwise false.</returns>
-        [RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
         public virtual bool Match(WeakReference<object?> reference)
         {
             reference.TryGetTarget(out var target);
@@ -43,7 +43,6 @@ namespace Avalonia.Data.Core.Plugins
         /// <returns>
         /// An observable that produces the output for the value.
         /// </returns>
-        [RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
         public virtual IObservable<object?> Start(WeakReference<object?> reference)
         {
             if (!reference.TryGetTarget(out var target) || target is null)
diff --git a/src/Avalonia.Base/Data/Core/Plugins/ObservableStreamPlugin`1.cs b/src/Avalonia.Base/Data/Core/Plugins/ObservableStreamPlugin`1.cs
new file mode 100644
index 000000000..3577911bc
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/Plugins/ObservableStreamPlugin`1.cs
@@ -0,0 +1,27 @@
+using System;
+using System.Linq;
+using Avalonia.Reactive;
+
+namespace Avalonia.Data.Core.Plugins;
+
+internal class ObservableStreamPlugin<T> : IStreamPlugin
+{
+    public bool Match(WeakReference<object?> reference)
+    {
+        return reference.TryGetTarget(out var target) && target is IObservable<T>;
+    }
+
+    public IObservable<object?> Start(WeakReference<object?> reference)
+    {
+        if (!(reference.TryGetTarget(out var target) && target is IObservable<T> obs))
+        {
+            return Observable.Empty<object?>();
+        }
+        else if (target is IObservable<object?> obj)
+        {
+            return obj;
+        }
+
+        return obs.Select(x => (object?)x);
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/Plugins/PropertyInfoAccessorPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/PropertyInfoAccessorPlugin.cs
new file mode 100644
index 000000000..9a79924f2
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/Plugins/PropertyInfoAccessorPlugin.cs
@@ -0,0 +1,27 @@
+using System;
+using System.Diagnostics;
+
+namespace Avalonia.Data.Core.Plugins;
+
+internal class PropertyInfoAccessorPlugin : IPropertyAccessorPlugin
+{
+    private readonly IPropertyInfo _propertyInfo;
+    private readonly Func<WeakReference<object?>, IPropertyInfo, IPropertyAccessor> _accessorFactory;
+
+    public PropertyInfoAccessorPlugin(IPropertyInfo propertyInfo, Func<WeakReference<object?>, IPropertyInfo, IPropertyAccessor> accessorFactory)
+    {
+        _propertyInfo = propertyInfo;
+        _accessorFactory = accessorFactory;
+    }
+
+    public bool Match(object obj, string propertyName)
+    {
+        throw new InvalidOperationException("The PropertyInfoAccessorPlugin does not support dynamic matching");
+    }
+
+    public IPropertyAccessor Start(WeakReference<object?> reference, string propertyName)
+    {
+        Debug.Assert(_propertyInfo.Name == propertyName);
+        return _accessorFactory(reference, _propertyInfo);
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/Plugins/ReflectionMethodAccessorPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/ReflectionMethodAccessorPlugin.cs
new file mode 100644
index 000000000..e295fc606
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/Plugins/ReflectionMethodAccessorPlugin.cs
@@ -0,0 +1,141 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq.Expressions;
+using System.Reflection;
+
+namespace Avalonia.Data.Core.Plugins
+{
+    [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
+    internal class ReflectionMethodAccessorPlugin : IPropertyAccessorPlugin
+    {
+        private readonly Dictionary<(Type, string), MethodInfo?> _methodLookup =
+            new Dictionary<(Type, string), MethodInfo?>();
+
+        public bool Match(object obj, string methodName) => GetFirstMethodWithName(obj.GetType(), methodName) != null;
+
+        public IPropertyAccessor? Start(WeakReference<object?> reference, string methodName)
+        {
+            _ = reference ?? throw new ArgumentNullException(nameof(reference));
+            _ = methodName ?? throw new ArgumentNullException(nameof(methodName));
+
+            if (!reference.TryGetTarget(out var instance) || instance is null)
+                return null;
+
+            var method = GetFirstMethodWithName(instance.GetType(), methodName);
+
+            if (method is not null)
+            {
+                return new Accessor(reference, method);
+            }
+            else
+            {
+                var message = $"Could not find CLR method '{methodName}' on '{instance}'";
+                var exception = new MissingMemberException(message);
+                return new PropertyError(new BindingNotification(exception, BindingErrorType.Error));
+            }
+        }
+
+        private MethodInfo? GetFirstMethodWithName(
+            [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods | DynamicallyAccessedMemberTypes.NonPublicMethods)] Type type, string methodName)
+        {
+            var key = (type, methodName);
+
+            if (!_methodLookup.TryGetValue(key, out var methodInfo))
+            {
+                methodInfo = TryFindAndCacheMethod(type, methodName);
+            }
+
+            return methodInfo;
+        }
+
+        private MethodInfo? TryFindAndCacheMethod(
+            [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods | DynamicallyAccessedMemberTypes.NonPublicMethods)] Type type, string methodName)
+        {
+            MethodInfo? found = null;
+
+            const BindingFlags bindingFlags =
+                BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static | BindingFlags.Instance;
+
+            var methods = type.GetMethods(bindingFlags);
+
+            foreach (var methodInfo in methods)
+            {
+                if (methodInfo.Name == methodName)
+                {
+                    var parameters = methodInfo.GetParameters();
+                    if (parameters.Length == 1 && parameters[0].ParameterType == typeof(object))
+                    {
+                        found = methodInfo;
+                        break;
+                    }
+                    else if (parameters.Length == 0)
+                    {
+                        found = methodInfo;
+                    }
+                }
+            }
+
+            _methodLookup.Add((type, methodName), found);
+
+            return found;
+        }
+
+        private sealed class Accessor : PropertyAccessorBase
+        {
+            public Accessor(WeakReference<object?> reference, MethodInfo method)
+            {
+                _ = reference ?? throw new ArgumentNullException(nameof(reference));
+                _ = method ?? throw new ArgumentNullException(nameof(method));
+
+                var returnType = method.ReturnType;
+
+                var parameters = method.GetParameters();
+
+                var signatureTypeCount = parameters.Length + 1;
+
+                var paramTypes = new Type[signatureTypeCount];
+
+
+                for (var i = 0; i < parameters.Length; i++)
+                {
+                    var parameter = parameters[i];
+
+                    paramTypes[i] = parameter.ParameterType;
+                }
+
+                paramTypes[paramTypes.Length - 1] = returnType;
+
+                PropertyType = Expression.GetDelegateType(paramTypes);
+
+                if (method.IsStatic)
+                {
+                    Value = method.CreateDelegate(PropertyType);
+                }
+                else if (reference.TryGetTarget(out var target))
+                {
+                    Value = method.CreateDelegate(PropertyType, target);
+                }
+            }
+
+            public override Type? PropertyType { get; }
+
+            public override object? Value { get; }
+
+            public override bool SetValue(object? value, BindingPriority priority) => false;
+
+            protected override void SubscribeCore()
+            {
+                try
+                {
+                    PublishValue(Value);
+                }
+                catch { }
+            }
+
+            protected override void UnsubscribeCore()
+            {
+            }
+        }
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/Plugins/TaskStreamPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/TaskStreamPlugin.cs
index 42a050778..56a7fcefe 100644
--- a/src/Avalonia.Base/Data/Core/Plugins/TaskStreamPlugin.cs
+++ b/src/Avalonia.Base/Data/Core/Plugins/TaskStreamPlugin.cs
@@ -10,6 +10,7 @@ namespace Avalonia.Data.Core.Plugins
     /// Handles binding to <see cref="Task"/>s for the '^' stream binding operator.
     /// </summary>
     [UnconditionalSuppressMessage("Trimming", "IL3050", Justification = TrimmingMessages.IgnoreNativeAotSupressWarningMessage)]
+    [RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
     internal class TaskStreamPlugin : IStreamPlugin
     {
         /// <summary>
@@ -17,7 +18,6 @@ namespace Avalonia.Data.Core.Plugins
         /// </summary>
         /// <param name="reference">A weak reference to the value.</param>
         /// <returns>True if the plugin can handle the value; otherwise false.</returns>
-        [RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
         public virtual bool Match(WeakReference<object?> reference)
         {
             reference.TryGetTarget(out var target);
@@ -32,7 +32,6 @@ namespace Avalonia.Data.Core.Plugins
         /// <returns>
         /// An observable that produces the output for the value.
         /// </returns>
-        [RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
         public virtual IObservable<object?> Start(WeakReference<object?> reference)
         {
             reference.TryGetTarget(out var target);
@@ -66,7 +65,7 @@ namespace Avalonia.Data.Core.Plugins
         private static IObservable<object?> HandleCompleted(Task task)
         {
             var resultProperty = task.GetType().GetRuntimeProperty("Result");
-            
+
             if (resultProperty != null)
             {
                 switch (task.Status)
diff --git a/src/Avalonia.Base/Data/Core/Plugins/TaskStreamPlugin`1.cs b/src/Avalonia.Base/Data/Core/Plugins/TaskStreamPlugin`1.cs
new file mode 100644
index 000000000..2746494b1
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/Plugins/TaskStreamPlugin`1.cs
@@ -0,0 +1,49 @@
+using System;
+using System.Threading.Tasks;
+using Avalonia.Reactive;
+
+namespace Avalonia.Data.Core.Plugins;
+
+internal class TaskStreamPlugin<T> : IStreamPlugin
+{
+    public bool Match(WeakReference<object?> reference)
+    {
+        return reference.TryGetTarget(out var target) && target is Task<T>;
+    }
+
+    public IObservable<object?> Start(WeakReference<object?> reference)
+    {
+        if (!(reference.TryGetTarget(out var target) && target is Task<T> task))
+        {
+            return Observable.Empty<object?>();
+        }
+
+        switch (task.Status)
+        {
+            case TaskStatus.RanToCompletion:
+            case TaskStatus.Faulted:
+                return HandleCompleted(task);
+            default:
+                var subject = new LightweightSubject<object?>();
+                task.ContinueWith(
+                        _ => HandleCompleted(task).Subscribe(subject),
+                        TaskScheduler.FromCurrentSynchronizationContext())
+                    .ConfigureAwait(false);
+                return subject;
+        }
+    }
+
+
+    private static IObservable<object?> HandleCompleted(Task<T> task)
+    {
+        switch (task.Status)
+        {
+            case TaskStatus.RanToCompletion:
+                return Observable.Return((object?)task.Result);
+            case TaskStatus.Faulted:
+                return Observable.Return(new BindingNotification(task.Exception!, BindingErrorType.Error));
+            default:
+                throw new AvaloniaInternalException("HandleCompleted called for non-completed Task.");
+        }
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/PropertyAccessorNode.cs b/src/Avalonia.Base/Data/Core/PropertyAccessorNode.cs
deleted file mode 100644
index ff20f241a..000000000
--- a/src/Avalonia.Base/Data/Core/PropertyAccessorNode.cs
+++ /dev/null
@@ -1,103 +0,0 @@
-using System;
-using System.Diagnostics.CodeAnalysis;
-using Avalonia.Data.Core.Plugins;
-
-namespace Avalonia.Data.Core
-{
-    [RequiresUnreferencedCode(TrimmingMessages.ExpressionNodeRequiresUnreferencedCodeMessage)]
-    internal class PropertyAccessorNode : SettableNode
-    {
-        private readonly bool _enableValidation;
-        private readonly IPropertyAccessorPlugin? _customPlugin;
-        private IPropertyAccessor? _accessor;
-
-        public PropertyAccessorNode(string propertyName, bool enableValidation)
-        {
-            PropertyName = propertyName;
-            _enableValidation = enableValidation;
-        }
-
-        public PropertyAccessorNode(string propertyName, bool enableValidation, IPropertyAccessorPlugin customPlugin)
-        {
-            PropertyName = propertyName;
-            _enableValidation = enableValidation;
-            _customPlugin = customPlugin;
-        }
-
-        public override string Description => PropertyName;
-        public string PropertyName { get; }
-        public override Type? PropertyType => _accessor?.PropertyType;
-
-        protected override bool SetTargetValueCore(object? value, BindingPriority priority)
-        {
-            if (_accessor != null)
-            {
-                try
-                {
-                    return _accessor.SetValue(value, priority);
-                }
-                catch { }
-            }
-
-            return false;
-        }
-
-        protected override void StartListeningCore(WeakReference<object?> reference)
-        {
-            if (!reference.TryGetTarget(out var target) || target is null)
-                return;
-
-            var plugin = _customPlugin ?? GetPropertyAccessorPluginForObject(target);
-            var accessor = plugin?.Start(reference, PropertyName);
-
-            // We need to handle accessor fallback before handling validation. Validators do not support null accessors.
-            if (accessor == null)
-            {
-                reference.TryGetTarget(out var instance);
-
-                var message = $"Could not find a matching property accessor for '{PropertyName}' on '{instance}'";
-
-                var exception = new MissingMemberException(message);
-
-                accessor = new PropertyError(new BindingNotification(exception, BindingErrorType.Error));
-            }
-
-            if (_enableValidation && Next == null)
-            {
-                foreach (var validator in ExpressionObserver.DataValidators)
-                {
-                    if (validator.Match(reference, PropertyName))
-                    {
-                        accessor = validator.Start(reference, PropertyName, accessor);
-                    }
-                }
-            }
-
-            if (accessor is null)
-            {
-                throw new AvaloniaInternalException("Data validators must return non-null accessor.");
-            }
-
-            _accessor = accessor;
-            accessor.Subscribe(ValueChanged);
-        }
-
-        private IPropertyAccessorPlugin? GetPropertyAccessorPluginForObject(object target)
-        {
-            foreach (IPropertyAccessorPlugin x in ExpressionObserver.PropertyAccessors)
-            {
-                if (x.Match(target, PropertyName))
-                {
-                    return x;
-                }
-            }
-            return null;
-        }
-
-        protected override void StopListeningCore()
-        {
-            _accessor?.Dispose();
-            _accessor = null;
-        }
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/SettableNode.cs b/src/Avalonia.Base/Data/Core/SettableNode.cs
deleted file mode 100644
index 4980e4487..000000000
--- a/src/Avalonia.Base/Data/Core/SettableNode.cs
+++ /dev/null
@@ -1,53 +0,0 @@
-using System;
-
-namespace Avalonia.Data.Core
-{
-    internal abstract class SettableNode : ExpressionNode
-    {
-        public bool SetTargetValue(object? value, BindingPriority priority)
-        {
-            if (ShouldNotSet(value))
-            {
-                return true;
-            }
-            return SetTargetValueCore(value, priority);
-        }
-
-        private bool ShouldNotSet(object? value)
-        {
-            var propertyType = PropertyType;
-            if (propertyType == null)
-            {
-                return false;
-            }
-
-            if (LastValue == null)
-            {
-                return false;
-            }
-
-            bool isLastValueAlive = LastValue.TryGetTarget(out var lastValue);
-
-            if (!isLastValueAlive)
-            {
-                if (value == null && LastValue == NullReference)
-                {
-                    return true;
-                }
-
-                return false;
-            }
-
-            if (propertyType.IsValueType)
-            {
-                return Equals(lastValue, value);
-            }
-
-            return ReferenceEquals(lastValue, value);
-        }
-
-        protected abstract bool SetTargetValueCore(object? value, BindingPriority priority);
-
-        public abstract Type? PropertyType { get; }
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/StreamNode.cs b/src/Avalonia.Base/Data/Core/StreamNode.cs
deleted file mode 100644
index 3db5da2c7..000000000
--- a/src/Avalonia.Base/Data/Core/StreamNode.cs
+++ /dev/null
@@ -1,56 +0,0 @@
-using System;
-using System.Diagnostics.CodeAnalysis;
-using Avalonia.Data.Core.Plugins;
-using Avalonia.Reactive;
-
-namespace Avalonia.Data.Core
-{
-    [RequiresUnreferencedCode(TrimmingMessages.ExpressionNodeRequiresUnreferencedCodeMessage)]
-    internal class StreamNode : ExpressionNode
-    {
-        private readonly IStreamPlugin? _customPlugin = null;
-        private IDisposable? _subscription;
-
-        public override string Description => "^";
-
-        public StreamNode() { }
-
-        public StreamNode(IStreamPlugin customPlugin)
-        {
-            _customPlugin = customPlugin;
-        }
-
-        protected override void StartListeningCore(WeakReference<object?> reference)
-        {
-            _subscription = GetPlugin(reference)?.Start(reference).Subscribe(ValueChanged);
-        }
-
-        protected override void StopListeningCore()
-        {
-            _subscription?.Dispose();
-            _subscription = null;
-        }
-
-        private IStreamPlugin? GetPlugin(WeakReference<object?> reference)
-        {
-            if (_customPlugin != null)
-            {
-                return _customPlugin;
-            }
-
-            foreach (var plugin in ExpressionObserver.StreamHandlers)
-            {
-                if (plugin.Match(reference))
-                {
-                    return plugin;
-                }
-            }
-
-            // TODO: Improve error
-            ValueChanged(new BindingNotification(
-                new MarkupBindingChainException("Stream operator applied to unsupported type", Description),
-                BindingErrorType.Error));
-            return null;
-        }
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/TargetTypeConverter.cs b/src/Avalonia.Base/Data/Core/TargetTypeConverter.cs
new file mode 100644
index 000000000..f63309486
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/TargetTypeConverter.cs
@@ -0,0 +1,127 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using System.Globalization;
+using Avalonia.Data.Converters;
+using System.Windows.Input;
+using Avalonia.Utilities;
+using static Avalonia.Utilities.TypeUtilities;
+
+namespace Avalonia.Data.Core;
+
+internal abstract class TargetTypeConverter
+{
+    private static TargetTypeConverter? s_default;
+    private static TargetTypeConverter? s_reflection;
+
+    public static TargetTypeConverter GetDefaultConverter() => s_default ??= new DefaultConverter();
+
+    [RequiresUnreferencedCode(TrimmingMessages.TypeConversionRequiresUnreferencedCodeMessage)]
+    public static TargetTypeConverter GetReflectionConverter() => s_reflection ??= new ReflectionConverter();
+
+    public abstract bool TryConvert(object? value, Type type, CultureInfo culture, out object? result);
+
+    private class DefaultConverter : TargetTypeConverter
+    {
+        public override bool TryConvert(object? value, Type type, CultureInfo culture, out object? result)
+        {
+            if (value?.GetType() == type)
+            {
+                result = value;
+                return true;
+            }
+
+            var t = Nullable.GetUnderlyingType(type) ?? type;
+
+            if (value is null)
+            {
+                result = null;
+                return !t.IsValueType || t != type;
+            }
+
+            if (value == AvaloniaProperty.UnsetValue)
+            {
+                // Here the behavior is different from the ReflectionConverter: there isn't any way
+                // to create the default value for a type without using reflection, so we have to report
+                // that we can't convert the value.
+                result = null;
+                return false;
+            }
+
+            if (t.IsAssignableFrom(value.GetType()))
+            {
+                result = value;
+                return true;
+            }
+
+            if (t == typeof(string))
+            {
+                result = value.ToString();
+                return true;
+            }
+
+            if (t.IsEnum && t.GetEnumUnderlyingType() == value.GetType())
+            {
+                result = Enum.ToObject(t, value);
+                return true;
+            }
+
+            if (value is IConvertible convertible)
+            {
+                try
+                {
+                    result = convertible.ToType(t, culture);
+                    return true;
+                }
+                catch
+                {
+                    result = null;
+                    return false;
+                }
+            }
+
+            // TODO: This requires reflection: we probably need to make compiled bindings emit
+            // conversion code at compile-time.
+            if (FindTypeConversionOperatorMethod(
+                value.GetType(), 
+                t, 
+                OperatorType.Implicit | OperatorType.Explicit) is { } cast)
+            {
+                result = cast.Invoke(null, new[] { value });
+                return true;
+            }
+
+            result = null;
+            return false;
+        }
+    }
+
+    [RequiresUnreferencedCode(TrimmingMessages.TypeConversionRequiresUnreferencedCodeMessage)]
+    private class ReflectionConverter : TargetTypeConverter
+    {
+        public override bool TryConvert(object? value, Type type, CultureInfo culture, out object? result)
+        {
+            if (value?.GetType() == type)
+            {
+                result = value;
+                return true;
+            }
+            else if (value == AvaloniaProperty.UnsetValue)
+            {
+                result = Activator.CreateInstance(type);
+                return true;
+            }
+            else if (typeof(ICommand).IsAssignableFrom(type) && 
+                value is Delegate d &&
+                !d.Method.IsPrivate &&
+                d.Method.GetParameters().Length <= 1)
+            {
+                result = new MethodToCommandConverter(d);
+                return true;
+            }
+            else
+            {
+                return TypeUtilities.TryConvert(type, value, culture, out result);
+            }
+        }
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/TypeCastNode.cs b/src/Avalonia.Base/Data/Core/TypeCastNode.cs
deleted file mode 100644
index 655bfbc7a..000000000
--- a/src/Avalonia.Base/Data/Core/TypeCastNode.cs
+++ /dev/null
@@ -1,34 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Text;
-
-namespace Avalonia.Data.Core
-{
-    internal class TypeCastNode : ExpressionNode
-    {
-        public override string Description => $"as {TargetType.FullName}";
-
-        public Type TargetType { get; }
-
-        public TypeCastNode(Type type)
-        {
-            TargetType = type;
-        }
-
-        protected virtual object? Cast(object? value)
-        {
-            return TargetType.IsInstanceOfType(value) ? value : null;
-        }
-
-        protected override void StartListeningCore(WeakReference<object?> reference)
-        {
-            if (reference.TryGetTarget(out var target))
-            {
-                target = Cast(target);
-                reference = target == null ? NullReference : new WeakReference<object?>(target);
-            }
-
-            base.StartListeningCore(reference);
-        }
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/UntypedBindingExpressionBase.cs b/src/Avalonia.Base/Data/Core/UntypedBindingExpressionBase.cs
new file mode 100644
index 000000000..5c7ea9459
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/UntypedBindingExpressionBase.cs
@@ -0,0 +1,600 @@
+using System;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
+using System.Globalization;
+using Avalonia.Data.Converters;
+using Avalonia.Logging;
+using Avalonia.Metadata;
+using Avalonia.PropertyStore;
+using Avalonia.Reactive;
+using Avalonia.Threading;
+using Avalonia.Utilities;
+
+namespace Avalonia.Data.Core;
+
+/// <summary>
+/// Base class for binding expressions which produce untyped values.
+/// </summary>
+[PrivateApi]
+public abstract class UntypedBindingExpressionBase : BindingExpressionBase,
+    IDisposable,
+    IDescription,
+    IValueEntry
+{
+    protected static readonly object UnchangedValue = new();
+    private readonly bool _isDataValidationEnabled;
+    private object? _defaultValue;
+    private BindingError? _error;
+    private ImmediateValueFrame? _frame;
+    private bool _isDefaultValueInitialized;
+    private bool _isRunning;
+    private bool _produceValue;
+    private IBindingExpressionSink? _sink;
+    private WeakReference<AvaloniaObject?>? _target;
+    private object? _value = AvaloniaProperty.UnsetValue;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="UntypedBindingExpressionBase"/> class.
+    /// </summary>
+    /// <param name="defaultPriority">
+    /// The default binding priority for the expression.
+    /// </param>
+    /// <param name="isDataValidationEnabled">Whether data validation is enabled.</param>
+    public UntypedBindingExpressionBase(
+        BindingPriority defaultPriority,
+        bool isDataValidationEnabled = false)
+    {
+        Priority = defaultPriority;
+        _isDataValidationEnabled = isDataValidationEnabled;
+    }
+
+    /// <summary>
+    /// Gets a description of the binding expression.
+    /// </summary>
+    public abstract string Description { get; }
+
+    /// <summary>
+    /// Gets the current error state of the binding expression.
+    /// </summary>
+    public BindingErrorType ErrorType => _error?.ErrorType ?? BindingErrorType.None;
+
+    /// <summary>
+    /// Gets a value indicating whether data validation is enabled for the binding expression.
+    /// </summary>
+    public bool IsDataValidationEnabled => _isDataValidationEnabled;
+
+    /// <summary>
+    /// Gets a value indicating whether the binding expression is currently running.
+    /// </summary>
+    public bool IsRunning => _isRunning;
+
+    /// <summary>
+    /// Gets the priority of the binding expression.
+    /// </summary>
+    /// <remarks>
+    /// Before being attached to a value store, this property describes the default priority of the
+    /// binding expression; this may change when the expression is attached to a value store.
+    /// </remarks>
+    public BindingPriority Priority { get; private set; }
+
+    /// <summary>
+    /// Gets the <see cref="AvaloniaProperty"/> which the binding expression is targeting.
+    /// </summary>
+    public AvaloniaProperty? TargetProperty { get; private set; }
+
+    /// <summary>
+    /// Gets the target type of the binding expression; that is, the type that values produced by
+    /// the expression should be converted to.
+    /// </summary>
+    public Type TargetType { get; private set; } = typeof(object);
+
+    AvaloniaProperty IValueEntry.Property => TargetProperty ?? throw new Exception();
+
+    /// <summary>
+    /// Terminates the binding.
+    /// </summary>
+    public override void Dispose()
+    {
+        if (_sink is null)
+            return;
+
+        Stop();
+
+        var sink = _sink;
+        var frame = _frame;
+        _sink = null;
+        _frame = null;
+        sink.OnCompleted(this);
+        frame?.OnEntryDisposed(this);
+    }
+
+    /// <summary>
+    /// Gets the current value of the binding expression.
+    /// </summary>
+    /// <returns>
+    /// The current value or <see cref="AvaloniaProperty.UnsetValue"/> if the binding was unable
+    /// to read a value.
+    /// </returns>
+    /// <exception cref="InvalidOperationException">
+    /// The binding expression has not been started.
+    /// </exception>
+    public object? GetValue()
+    {
+        if (!IsRunning)
+            throw new InvalidOperationException("BindingExpression has not been started.");
+        return _value;
+    }
+
+    /// <summary>
+    /// Gets the current value of the binding expression or the default value for the target property.
+    /// </summary>
+    /// <returns>
+    /// The current value or the target property default.
+    /// </returns>
+    public object? GetValueOrDefault()
+    {
+        var result = GetValue();
+        if (result == AvaloniaProperty.UnsetValue)
+            result = GetCachedDefaultValue();
+        return result;
+    }
+
+    /// <summary>
+    /// Starts the binding expression following a call to 
+    /// <see cref="AttachCore(IBindingExpressionSink, AvaloniaObject, AvaloniaProperty, BindingPriority)"/>.
+    /// </summary>
+    public void Start() => Start(produceValue: true);
+
+    bool IValueEntry.GetDataValidationState(out BindingValueType state, out Exception? error)
+    {
+        if (_error is not null)
+        {
+            state = _error.ErrorType switch
+            {
+                BindingErrorType.Error => BindingValueType.BindingError,
+                BindingErrorType.DataValidationError => BindingValueType.DataValidationError,
+                _ => throw new InvalidOperationException("Invalid BindingErrorType."),
+            };
+            error = _error.Exception;
+        }
+        else
+        {
+            state = BindingValueType.Value;
+            error = null;
+        }
+
+        return IsDataValidationEnabled;
+    }
+
+    bool IValueEntry.HasValue()
+    {
+        Start(produceValue: false);
+        return true;
+    }
+
+    object? IValueEntry.GetValue()
+    {
+        Start(produceValue: false);
+        return GetValueOrDefault();
+    }
+
+    void IValueEntry.Unsubscribe() => Stop();
+
+    internal override void Attach(
+        ValueStore valueStore,
+        ImmediateValueFrame? frame,
+        AvaloniaObject target,
+        AvaloniaProperty targetProperty,
+        BindingPriority priority)
+    {
+        AttachCore(valueStore, frame, target, targetProperty, priority);
+    }
+
+    /// <summary>
+    /// Initializes the binding expression with the specified subscriber and target property and
+    /// starts it.
+    /// </summary>
+    /// <param name="subscriber">The subscriber.</param>
+    /// <param name="target">The target object.</param>
+    /// <param name="targetProperty">The target property.</param>
+    /// <param name="priority">The priority of the binding.</param>
+    internal void AttachAndStart(
+        IBindingExpressionSink subscriber,
+        AvaloniaObject target,
+        AvaloniaProperty targetProperty,
+        BindingPriority priority)
+    {
+        AttachCore(subscriber, null, target, targetProperty, priority);
+        Start(produceValue: true);
+    }
+
+    /// <summary>
+    /// Produces an observable which can be used to observe the value of the binding expression.
+    /// </summary>
+    /// <param name="target">The binding target, if known.</param>
+    /// <returns>An observable subject.</returns>
+    /// <exception cref="InvalidOperationException">
+    /// The binding expression is already instantiated on an AvaloniaObject.
+    /// </exception>
+    /// <remarks>
+    /// This method is mostly here for backwards compatibility with <see cref="InstancedBinding"/>
+    /// and unit testing and we may want to remove it in future. In particular its usefulness in
+    /// terms of unit testing is limited in that it preserves the semantics of binding expressions
+    /// as expected by unit tests, not necessarily the semantics that will be used when the
+    /// expression is used as an <see cref="IValueEntry"/> instantiated in a
+    /// <see cref="ValueStore"/>. Unit tests should be migrated to not test the behaviour of
+    /// binding expressions through an observable, and instead test the behaviour of the binding
+    /// when applied to an <see cref="AvaloniaObject"/>.
+    /// 
+    /// A binding expression may only act as an observable or as a binding expression targeting an
+    /// AvaloniaObject, not both.
+    /// </remarks>
+    internal IAvaloniaSubject<object?> ToObservable(AvaloniaObject? target = null)
+    {
+        if (_sink is ObservableSink s)
+            return s;
+        if (_sink is not null)
+            throw new InvalidOperationException(
+                "Cannot call AsObservable on a to binding expression which is already " +
+                "instantiated on an AvaloniaObject.");
+
+        var o = new ObservableSink(this);
+        _sink = o;
+        _target = target is not null ? new(target) : null;
+        return o;
+    }
+
+    /// <summary>
+    /// When overridden in a derived class, writes the specified value to the binding source if
+    /// possible.
+    /// </summary>
+    /// <param name="value">The value to write.</param>
+    /// <returns>
+    /// True if the value could be written to the binding source; otherwise false.
+    /// </returns>
+    internal virtual bool WriteValueToSource(object? value) => false;
+
+    private void AttachCore(
+        IBindingExpressionSink sink,
+        ImmediateValueFrame? frame,
+        AvaloniaObject target,
+        AvaloniaProperty targetProperty,
+        BindingPriority priority)
+    {
+        if (_sink is not null)
+            throw new InvalidOperationException("BindingExpression was already attached.");
+
+        _sink = sink;
+        _frame = frame;
+        _target = new(target);
+        TargetProperty = targetProperty;
+        TargetType = targetProperty.PropertyType;
+        Priority = priority;
+    }
+
+
+    /// <summary>
+    /// Converts a value using a value converter, logging a warning if necessary.
+    /// </summary>
+    /// <param name="converter">The value converter.</param>
+    /// <param name="converterCulture">The culture to use for the conversion.</param>
+    /// <param name="converterParameter">The converter parameter.</param>
+    /// <param name="value">The value to convert.</param>
+    /// <param name="targetType">The target type to convert to.</param>
+    /// <param name="error">The current error state.</param>
+    /// <returns>
+    /// The converted value, or <see cref="AvaloniaProperty.UnsetValue"/> if an error occurred;
+    /// in which case the error state will logged and updated in <paramref name="error"/>.
+    /// </returns>
+    private protected object? Convert(
+        IValueConverter converter,
+        CultureInfo? converterCulture,
+        object? converterParameter,
+        object? value,
+        Type targetType,
+        ref BindingError? error)
+    {
+        try
+        {
+            return converter.Convert(
+                value,
+                targetType,
+                converterParameter,
+                converterCulture ?? CultureInfo.CurrentCulture);
+        }
+        catch (Exception e)
+        {
+            var valueString = value?.ToString() ?? "(null)";
+            var valueTypeName = value?.GetType().FullName ?? "null";
+            var message = $"Could not convert '{valueString}' ({valueTypeName}) to '{targetType}' using '{converter}'";
+
+            if (ShouldLogError(out var target))
+                Log(target, $"{message}: {e.Message}", LogEventLevel.Warning);
+
+            error = new(new InvalidCastException(message + '.', e), BindingErrorType.Error);
+            return AvaloniaProperty.UnsetValue;
+        }
+    }
+
+    /// <summary>
+    /// Converts a value using a value converter's ConvertBack method, logging a warning if
+    /// necessary.
+    /// </summary>
+    /// <param name="converter">The value converter.</param>
+    /// <param name="converterCulture">The culture to use for the conversion.</param>
+    /// <param name="converterParameter">The converter parameter.</param>
+    /// <param name="value">The value to convert.</param>
+    /// <param name="targetType">The target type to convert to.</param>
+    /// <returns>
+    /// The converted value, or <see cref="AvaloniaProperty.UnsetValue"/> if an error occurred;
+    /// in which case the error will be logged.
+    /// </returns>
+    protected object? ConvertBack(
+        IValueConverter converter,
+        CultureInfo? converterCulture,
+        object? converterParameter,
+        object? value,
+        Type targetType)
+    {
+        try
+        {
+            return converter.ConvertBack(
+                value,
+                targetType,
+                converterParameter,
+                converterCulture ?? CultureInfo.CurrentCulture);
+        }
+        catch (Exception e)
+        {
+            var valueString = value?.ToString() ?? "(null)";
+            var valueTypeName = value?.GetType().FullName ?? "null";
+            var message = $"Could not convert '{valueString}' ({valueTypeName}) to '{targetType}' using '{converter}'";
+
+            if (ShouldLogError(out var target))
+                Log(target, $"{message}: {e.Message}", LogEventLevel.Warning);
+
+            return AvaloniaProperty.UnsetValue;
+        }
+    }
+
+    /// <summary>
+    /// Logs a binding error.
+    /// </summary>
+    /// <param name="error">The error message.</param>
+    /// <param name="level">The log level.</param>
+    protected void Log(string error, LogEventLevel level = LogEventLevel.Warning)
+    {
+        if (!TryGetTarget(out var target))
+            return;
+
+        if (!Logger.TryGet(level, LogArea.Binding, out var log))
+            return;
+
+        log.Log(
+            target,
+            "An error occurred binding {Property} to {Expression}: {Message}",
+            (object?)TargetProperty ?? "(unknown)",
+            Description,
+            error);
+    }
+
+    /// <summary>
+    /// Logs a binding error.
+    /// </summary>
+    /// <param name="target">The target of the binding expression.</param>
+    /// <param name="error">The error message.</param>
+    /// <param name="level">The log level.</param>
+    protected void Log(AvaloniaObject target, string error, LogEventLevel level = LogEventLevel.Warning)
+    {
+        if (!Logger.TryGet(level, LogArea.Binding, out var log))
+            return;
+
+        log.Log(
+            target,
+            "An error occurred binding {Property} to {Expression}: {Message}",
+            (object?)TargetProperty ?? "(unknown)",
+            Description,
+            error);
+    }
+
+    /// <summary>
+    /// Publishes a new value and/or error state to the target.
+    /// </summary>
+    /// <param name="value">The new value, or <see cref="UnchangedValue"/>.</param>
+    /// <param name="error">The new binding or data validation error.</param>
+    private protected void PublishValue(object? value, BindingError? error = null)
+    {
+        // When binding to DataContext and the expression results in a binding error, the binding
+        // expression should produce null rather than UnsetValue in order to not propagate
+        // incorrect DataContexts from parent controls while things are being set up.
+        if (TargetProperty == StyledElement.DataContextProperty &&
+            value == AvaloniaProperty.UnsetValue &&
+            error?.ErrorType == BindingErrorType.Error)
+        {
+            value = null;
+        }
+
+        var hasValueChanged = value != UnchangedValue && !TypeUtilities.IdentityEquals(value, GetValue(), TargetType);
+        var hasErrorChanged = error is not null || _error is not null;
+
+        if (hasValueChanged)
+            _value = value;
+        _error = error;
+
+        if (!_produceValue || _sink is null)
+            return;
+
+        if (Dispatcher.UIThread.CheckAccess())
+        {
+            _sink.OnChanged(this, hasValueChanged, hasErrorChanged, GetValueOrDefault(), _error);
+        }
+        else
+        {
+            // To avoid allocating closure in the outer scope we need to capture variables
+            // locally. This allows us to skip most of the allocations when on UI thread.
+            var sink = _sink;
+            var vc = hasValueChanged;
+            var ec = hasErrorChanged;
+            var v = GetValueOrDefault();
+            var e = _error;
+            Dispatcher.UIThread.Post(() => sink.OnChanged(this, vc, ec, v, e));
+        }
+    }
+
+    /// <summary>
+    /// Gets a value indicating whether an error should be logged given the current state of the
+    /// binding expression.
+    /// </summary>
+    /// <param name="target">
+    /// When the method returns, contains the target object, if it is available.
+    /// </param>
+    /// <returns>True if an error should be logged; otherwise false.</returns>
+    protected virtual bool ShouldLogError([NotNullWhen(true)] out AvaloniaObject? target)
+    {
+        return TryGetTarget(out target);
+    }
+
+    /// <summary>
+    /// Starts the binding expression by calling <see cref="StartCore"/>.
+    /// </summary>
+    /// <param name="produceValue">
+    /// Indicates whether the binding expression should produce an initial value.
+    /// </param>
+    protected void Start(bool produceValue)
+    {
+        if (_isRunning)
+            return;
+
+        _isRunning = true;
+
+        try
+        {
+            _produceValue = produceValue;
+            StartCore();
+        }
+        finally
+        {
+            _produceValue = true;
+        }
+    }
+
+    /// <summary>
+    /// When overridden in a derived class, starts the binding expression.
+    /// </summary>
+    /// <remarks>
+    /// This method should not be called directly; instead call <see cref="Start(bool)"/>.
+    /// </remarks>
+    protected abstract void StartCore();
+
+    /// <summary>
+    /// Stops the binding expression by calling <see cref="StopCore"/>.
+    /// </summary>
+    protected void Stop()
+    {
+        if (!_isRunning)
+            return;
+
+        StopCore();
+        _isRunning = false;
+        _value = AvaloniaProperty.UnsetValue;
+    }
+
+    /// <summary>
+    /// When overridden in a derived class, stops the binding expression.
+    /// </summary>
+    /// <remarks>
+    /// This method should not be called directly; instead call <see cref="Stop"/>.
+    /// </remarks>
+    protected abstract void StopCore();
+
+    /// <summary>
+    /// Tries to retrieve the target for the binding expression.
+    /// </summary>
+    /// <param name="target">
+    /// When this method returns, contains the target object, if it is available.
+    /// </param>
+    /// <returns>true if the target was retrieved; otherwise, false.</returns>
+    protected bool TryGetTarget([NotNullWhen(true)] out AvaloniaObject? target)
+    {
+        if (_target is not null)
+            return _target.TryGetTarget(out target);
+        target = null!;
+        return false;
+    }
+
+    private object? GetCachedDefaultValue()
+    {
+        if (_isDefaultValueInitialized == true)
+            return _defaultValue;
+
+        if (TargetProperty is not null && _target?.TryGetTarget(out var target) == true)
+        {
+            if (TargetProperty.IsDirect)
+                _defaultValue = ((IDirectPropertyAccessor)TargetProperty).GetUnsetValue(target.GetType());
+            else
+                _defaultValue = ((IStyledPropertyAccessor)TargetProperty).GetDefaultValue(target.GetType());
+
+            _isDefaultValueInitialized = true;
+            return _defaultValue;
+        }
+
+        return AvaloniaProperty.UnsetValue;
+    }
+
+    private sealed class ObservableSink : LightweightObservableBase<object?>,
+        IBindingExpressionSink,
+        IAvaloniaSubject<object?>
+    {
+        private readonly UntypedBindingExpressionBase _expression;
+        private object? _value = AvaloniaProperty.UnsetValue;
+
+        public ObservableSink(UntypedBindingExpressionBase expression) => _expression = expression;
+
+        void IBindingExpressionSink.OnChanged(
+            UntypedBindingExpressionBase instance,
+            bool hasValueChanged,
+            bool hasErrorChanged,
+            object? value,
+            BindingError? error)
+        {
+            if (instance.IsDataValidationEnabled || error is not null)
+            {
+                BindingNotification notification;
+
+                if (error?.ErrorType == BindingErrorType.Error)
+                    notification = new(error.Exception, BindingErrorType.Error, value);
+                else if (error?.ErrorType == BindingErrorType.DataValidationError)
+                    notification = new(error.Exception, BindingErrorType.DataValidationError, value);
+                else
+                    notification = new(value);
+
+                PublishNext(notification);
+            }
+            else if (hasValueChanged)
+            {
+                PublishNext(value);
+            }
+        }
+
+        void IBindingExpressionSink.OnCompleted(UntypedBindingExpressionBase instance) => PublishCompleted();
+
+        void IObserver<object?>.OnCompleted() { }
+        void IObserver<object?>.OnError(Exception error) { }
+        void IObserver<object?>.OnNext(object? value) => _expression.WriteValueToSource(value);
+
+        protected override void Initialize() => _expression.Start(produceValue: true);
+        protected override void Deinitialize() => _expression.Stop();
+
+        protected override void Subscribed(IObserver<object> observer, bool first)
+        {
+            if (!first && _value != AvaloniaProperty.UnsetValue)
+                base.PublishNext(_value);
+        }
+
+        private new void PublishNext(object? value)
+        {
+            _value = value;
+            base.PublishNext(value);
+        }
+    }
+}
diff --git a/src/Avalonia.Base/Data/Core/UntypedObservableBindingExpression.cs b/src/Avalonia.Base/Data/Core/UntypedObservableBindingExpression.cs
new file mode 100644
index 000000000..1e26caa05
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/UntypedObservableBindingExpression.cs
@@ -0,0 +1,34 @@
+using System;
+
+namespace Avalonia.Data.Core;
+
+internal class UntypedObservableBindingExpression : UntypedBindingExpressionBase, IObserver<object?>
+{
+    private readonly IObservable<object?> _observable;
+    private IDisposable? _subscription;
+
+    public UntypedObservableBindingExpression(
+        IObservable<object?> observable,
+        BindingPriority priority)
+        : base(priority)
+    {
+        _observable = observable;
+    }
+
+    public override string Description => "Observable";
+
+    protected override void StartCore()
+    {
+        _subscription = _observable.Subscribe(this);
+    }
+
+    protected override void StopCore()
+    {
+        _subscription?.Dispose();
+        _subscription = null;
+    }
+
+    void IObserver<object?>.OnCompleted() { }
+    void IObserver<object?>.OnError(Exception error) { }
+    void IObserver<object?>.OnNext(object? value) => PublishValue(value);
+}
diff --git a/src/Markup/Avalonia.Markup/Data/CultureInfoIetfLanguageTagConverter.cs b/src/Avalonia.Base/Data/CultureInfoIetfLanguageTagConverter.cs
similarity index 100%
rename from src/Markup/Avalonia.Markup/Data/CultureInfoIetfLanguageTagConverter.cs
rename to src/Avalonia.Base/Data/CultureInfoIetfLanguageTagConverter.cs
diff --git a/src/Avalonia.Base/Data/IBinding.cs b/src/Avalonia.Base/Data/IBinding.cs
index 01204c39c..e000da18f 100644
--- a/src/Avalonia.Base/Data/IBinding.cs
+++ b/src/Avalonia.Base/Data/IBinding.cs
@@ -1,3 +1,5 @@
+using System;
+using Avalonia.Diagnostics;
 using Avalonia.Metadata;
 
 namespace Avalonia.Data
@@ -23,6 +25,7 @@ namespace Avalonia.Data
         /// <returns>
         /// A <see cref="InstancedBinding"/> or null if the binding could not be resolved.
         /// </returns>
+        [Obsolete(ObsoletionMessages.MayBeRemovedInAvalonia12)]
         InstancedBinding? Initiate(
             AvaloniaObject target, 
             AvaloniaProperty? targetProperty,
diff --git a/src/Avalonia.Base/Data/IndexerBinding.cs b/src/Avalonia.Base/Data/IndexerBinding.cs
index a1b9e8b15..02bde6f77 100644
--- a/src/Avalonia.Base/Data/IndexerBinding.cs
+++ b/src/Avalonia.Base/Data/IndexerBinding.cs
@@ -1,8 +1,10 @@
-using Avalonia.Reactive;
+using System;
+using Avalonia.Data.Core;
+using Avalonia.Diagnostics;
 
 namespace Avalonia.Data
 {
-    internal class IndexerBinding : IBinding
+    internal class IndexerBinding : IBinding2
     {
         public IndexerBinding(
             AvaloniaObject source,
@@ -18,16 +20,20 @@ namespace Avalonia.Data
         public AvaloniaProperty Property { get; }
         private BindingMode Mode { get; }
 
+        [Obsolete(ObsoletionMessages.MayBeRemovedInAvalonia12)]
         public InstancedBinding? Initiate(
             AvaloniaObject target,
             AvaloniaProperty? targetProperty,
             object? anchor = null,
             bool enableDataValidation = false)
         {
-            var subject = new CombinedSubject<object?>(
-                new AnonymousObserver<object?>(x => Source.SetValue(Property, x, BindingPriority.LocalValue)),
-                Source.GetObservable(Property));
-            return new InstancedBinding(subject, Mode, BindingPriority.LocalValue);
+            var expression = new IndexerBindingExpression(Source, Property, target, targetProperty, Mode);
+            return new InstancedBinding(expression, Mode, BindingPriority.LocalValue);
+        }
+
+        BindingExpressionBase IBinding2.Instance(AvaloniaObject target, AvaloniaProperty targetProperty, object? anchor)
+        {
+            return new IndexerBindingExpression(Source, Property, target, targetProperty, Mode);
         }
     }
 }
diff --git a/src/Avalonia.Base/Data/InstancedBinding.cs b/src/Avalonia.Base/Data/InstancedBinding.cs
index 9bfaefbaf..158f426cb 100644
--- a/src/Avalonia.Base/Data/InstancedBinding.cs
+++ b/src/Avalonia.Base/Data/InstancedBinding.cs
@@ -1,5 +1,6 @@
 using System;
 using System.ComponentModel;
+using Avalonia.Data.Core;
 using Avalonia.Reactive;
 using ObservableEx = Avalonia.Reactive.Observable;
 
@@ -16,6 +17,10 @@ namespace Avalonia.Data
     /// </remarks>
     public sealed class InstancedBinding
     {
+        private readonly AvaloniaObject? _target;
+        private readonly UntypedBindingExpressionBase? _expression;
+        private IObservable<object?>? _observable;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="InstancedBinding"/> class.
         /// </summary>
@@ -32,7 +37,29 @@ namespace Avalonia.Data
         {
             Mode = mode;
             Priority = priority;
-            Source = source ?? throw new ArgumentNullException(nameof(source));
+            _observable = source ?? throw new ArgumentNullException(nameof(source));
+        }
+
+        internal InstancedBinding(
+            UntypedBindingExpressionBase source,
+            BindingMode mode,
+            BindingPriority priority)
+        {
+            Mode = mode;
+            Priority = priority;
+            _expression = source ?? throw new ArgumentNullException(nameof(source));
+        }
+
+        internal InstancedBinding(
+            AvaloniaObject? target,
+            UntypedBindingExpressionBase source, 
+            BindingMode mode, 
+            BindingPriority priority)
+        {
+            Mode = mode;
+            Priority = priority;
+            _expression = source ?? throw new ArgumentNullException(nameof(source));
+            _target = target;
         }
 
         /// <summary>
@@ -48,11 +75,13 @@ namespace Avalonia.Data
         /// <summary>
         /// Gets the binding source observable.
         /// </summary>
-        public IObservable<object?> Source { get; }
+        public IObservable<object?> Source => _observable ??= _expression!.ToObservable(_target);
 
         [Obsolete("Use Source property"), EditorBrowsable(EditorBrowsableState.Never)]
         public IObservable<object?> Observable => Source;
 
+        internal UntypedBindingExpressionBase? Expression => _expression;
+
         /// <summary>
         /// Creates a new one-time binding with a fixed value.
         /// </summary>
diff --git a/src/Avalonia.Base/Data/TemplateBinding.Observable.cs b/src/Avalonia.Base/Data/TemplateBinding.Observable.cs
new file mode 100644
index 000000000..21bf4430b
--- /dev/null
+++ b/src/Avalonia.Base/Data/TemplateBinding.Observable.cs
@@ -0,0 +1,21 @@
+using System;
+using Avalonia.Reactive;
+
+namespace Avalonia.Data
+{
+    // TODO12: Remove IAvaloniaSubject<object?> support from TemplateBinding.
+    public partial class TemplateBinding : IAvaloniaSubject<object?>
+    {
+        private IAvaloniaSubject<object?>? _observableAdapter;
+
+        public IDisposable Subscribe(IObserver<object?> observer)
+        {
+            _observableAdapter ??= ToObservable();
+            return _observableAdapter.Subscribe(observer);
+        }
+
+        void IObserver<object?>.OnCompleted() => _observableAdapter?.OnCompleted();
+        void IObserver<object?>.OnError(Exception error) => _observableAdapter?.OnError(error);
+        void IObserver<object?>.OnNext(object? value) => _observableAdapter?.OnNext(value);
+    }
+}
diff --git a/src/Avalonia.Base/Data/TemplateBinding.cs b/src/Avalonia.Base/Data/TemplateBinding.cs
index dd288b892..db878620b 100644
--- a/src/Avalonia.Base/Data/TemplateBinding.cs
+++ b/src/Avalonia.Base/Data/TemplateBinding.cs
@@ -1,101 +1,52 @@
 using System;
+using System.ComponentModel;
+using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using Avalonia.Data.Converters;
-using Avalonia.Reactive;
+using Avalonia.Data.Core;
+using Avalonia.Logging;
 using Avalonia.Styling;
-using Avalonia.Threading;
 
 namespace Avalonia.Data
 {
     /// <summary>
     /// A XAML binding to a property on a control's templated parent.
     /// </summary>
-    public class TemplateBinding : IObservable<object?>,
+    public partial class TemplateBinding : UntypedBindingExpressionBase,
         IBinding,
+        IBinding2,
         IDescription,
-        IAvaloniaSubject<object?>,
         ISetterValue,
         IDisposable
     {
-        private IObserver<object?>? _observer;
         private bool _isSetterValue;
-        private StyledElement? _target;
-        private Type? _targetType;
-        private bool _hasProducedValue;
 
         public TemplateBinding()
+            : base(BindingPriority.Template)
         {
         }
 
         public TemplateBinding(AvaloniaProperty property)
+            : base(BindingPriority.Template)
         {
             Property = property;
         }
 
-        public IDisposable Subscribe(IObserver<object?> observer)
-        {
-            _ = observer ?? throw new ArgumentNullException(nameof(observer));
-            Dispatcher.UIThread.VerifyAccess();
-
-            if (_observer != null)
-            {
-                throw new InvalidOperationException("The observable can only be subscribed once.");
-            }
-
-            _observer = observer;
-            Subscribed();
-
-            return this;
-        }
-
-        public virtual void Dispose()
-        {
-            Unsubscribed();
-            _observer = null;
-        }
-
-        /// <inheritdoc/>
-        public InstancedBinding? Initiate(
-            AvaloniaObject target,
-            AvaloniaProperty? targetProperty,
-            object? anchor = null,
-            bool enableDataValidation = false)
-        {
-            // Usually each `TemplateBinding` will only be instantiated once; in this case we can
-            // use the `TemplateBinding` object itself as the instanced binding in order to save
-            // allocating a new object.
-            //
-            // If the binding appears in a `Setter`, then make a clone and instantiate that because
-            // because the setter can outlive the control and cause a leak.
-            if (_target is null && !_isSetterValue)
-            {
-                _target = (StyledElement)target;
-                _targetType = targetProperty?.PropertyType;
-
-                return new InstancedBinding(
-                    this,
-                    Mode == BindingMode.Default ? BindingMode.OneWay : Mode,
-                    BindingPriority.Template);
-            }
-            else
-            {
-                var clone = new TemplateBinding
-                {
-                    Converter = Converter,
-                    ConverterParameter = ConverterParameter,
-                    Property = Property,
-                    Mode = Mode,
-                };
-
-                return clone.Initiate(target, targetProperty, anchor, enableDataValidation);
-            }
-        }
-
         /// <summary>
         /// Gets or sets the <see cref="IValueConverter"/> to use.
         /// </summary>
         public IValueConverter? Converter { get; set; }
 
+        /// <summary>
+        /// Gets or sets the culture in which to evaluate the converter.
+        /// </summary>
+        /// <value>The default value is null.</value>
+        /// <remarks>
+        /// If this property is not set then <see cref="CultureInfo.CurrentCulture"/> will be used.
+        /// </remarks>
+        [TypeConverter(typeof(CultureInfoIetfLanguageTagConverter))]
+        public CultureInfo? ConverterCulture { get; set; }
+
         /// <summary>
         /// Gets or sets a parameter to pass to <see cref="Converter"/>.
         /// </summary>
@@ -104,7 +55,11 @@ namespace Avalonia.Data
         /// <summary>
         /// Gets or sets the binding mode.
         /// </summary>
-        public BindingMode Mode { get; set; }
+        public new BindingMode Mode 
+        { 
+            get => base.Mode;
+            set => base.Mode = value;
+        }
 
         /// <summary>
         /// Gets or sets the name of the source property on the templated parent.
@@ -112,108 +67,187 @@ namespace Avalonia.Data
         public AvaloniaProperty? Property { get; set; }
 
         /// <inheritdoc/>
-        public string Description => "TemplateBinding: " + Property;
+        public override string Description => "TemplateBinding: " + Property;
 
-        void IObserver<object?>.OnCompleted() => throw new NotImplementedException();
-        void IObserver<object?>.OnError(Exception error) => throw new NotImplementedException();
+        public IBinding ProvideValue() => this;
 
-        void IObserver<object?>.OnNext(object? value)
+        public InstancedBinding? Initiate(
+            AvaloniaObject target,
+            AvaloniaProperty? targetProperty,
+            object? anchor = null,
+            bool enableDataValidation = false)
         {
-            if (_target?.TemplatedParent is { } templatedParent && Property is not null)
+            return new(target, InstanceCore(), Mode, BindingPriority.Template);
+        }
+
+        BindingExpressionBase IBinding2.Instance(AvaloniaObject target, AvaloniaProperty property, object? anchor)
+        {
+            return InstanceCore();
+        }
+
+        internal override bool WriteValueToSource(object? value)
+        {
+            if (Property is not null && TryGetTemplatedParent(out var templatedParent))
             {
                 if (Converter is not null)
-                {
-                    value = Converter.ConvertBack(
-                        value,
-                        Property.PropertyType,
-                        ConverterParameter,
-                        CultureInfo.CurrentCulture);
-                }
+                    value = ConvertBack(Converter, ConverterCulture, ConverterParameter, value, TargetType);
 
-                templatedParent.SetCurrentValue(Property, value);
+                if (value != BindingOperations.DoNothing)
+                    templatedParent.SetCurrentValue(Property, value);
+
+                return true;
             }
+
+            return false;
         }
 
         /// <inheritdoc/>
         void ISetterValue.Initialize(SetterBase setter) => _isSetterValue = true;
 
-        private void Subscribed()
+        protected override void StartCore()
         {
-            TemplatedParentChanged();
+            OnTemplatedParentChanged();
+            if (TryGetTarget(out var target))
+                target.PropertyChanged += OnTargetPropertyChanged;
+        }
 
-            if (_target is not null)
+        protected override void StopCore()
+        {
+            if (TryGetTarget(out var target))
             {
-                _target.PropertyChanged += TargetPropertyChanged;
+                if (target is StyledElement targetElement &&
+                    targetElement?.TemplatedParent is { } templatedParent)
+                {
+                    templatedParent.PropertyChanged -= OnTemplatedParentPropertyChanged;
+                }
+
+                if (target is not null)
+                {
+                    target.PropertyChanged -= OnTargetPropertyChanged;
+                }
             }
         }
 
-        private void Unsubscribed()
+        private object? ConvertToTargetType(object? value)
         {
-            if (_target?.TemplatedParent is { } templatedParent)
-            {
-                templatedParent.PropertyChanged -= TemplatedParentPropertyChanged;
-            }
+            var converter = TargetTypeConverter.GetDefaultConverter();
 
-            if (_target is not null)
+            if (converter.TryConvert(value, TargetType, CultureInfo.InvariantCulture, out var result))
             {
-                _target.PropertyChanged -= TargetPropertyChanged;
+                return result;
+            }
+            else
+            {
+                if (TryGetTarget(out var target))
+                {
+                    var valueString = value?.ToString() ?? "(null)";
+                    var valueTypeName = value?.GetType().FullName ?? "null";
+                    var message = $"Could not convert '{valueString}' ({valueTypeName}) to '{TargetType}'.";
+                    Log(target, message, LogEventLevel.Warning);
+                }
+
+                return AvaloniaProperty.UnsetValue;
+            }
+        }
+
+        private TemplateBinding InstanceCore()
+        {
+            if (Mode is BindingMode.OneTime or BindingMode.OneWayToSource)
+                throw new NotSupportedException("TemplateBinding does not support OneTime or OneWayToSource bindings.");
+
+            // Usually each `TemplateBinding` will only be instantiated once; in this case we can
+            // use the `TemplateBinding` object itself as the binding expression in order to save
+            // allocating a new object.
+            //
+            // If the binding appears in a `Setter`, then make a clone and instantiate that because
+            // because the setter can outlive the control and cause a leak.
+            if (!_isSetterValue)
+            {
+                return this;
+            }
+            else
+            {
+                var clone = new TemplateBinding
+                {
+                    Converter = Converter,
+                    ConverterCulture = ConverterCulture,
+                    ConverterParameter = ConverterParameter,
+                    Mode = Mode,
+                    Property = Property,
+                };
+
+                return clone;
             }
         }
 
         private void PublishValue()
         {
-            if (_target?.TemplatedParent is { } templatedParent)
+            if (Mode == BindingMode.OneWayToSource)
+                return;
+
+            if (TryGetTemplatedParent(out var templatedParent))
             {
                 var value = Property is not null ?
                     templatedParent.GetValue(Property) :
-                    _target.TemplatedParent;
+                    templatedParent;
+                BindingError? error = null;
 
                 if (Converter is not null)
-                {
-                    value = Converter.Convert(value, _targetType ?? typeof(object), ConverterParameter, CultureInfo.CurrentCulture);
-                }
+                    value = Convert(Converter, ConverterCulture, ConverterParameter, value, TargetType, ref error);
 
-                _observer?.OnNext(value);
-                _hasProducedValue = true;
+                value = ConvertToTargetType(value);
+                PublishValue(value, error);
+
+                if (Mode == BindingMode.OneTime)
+                    Stop();
             }
-            else if (_hasProducedValue)
+            else
             {
-                _observer?.OnNext(AvaloniaProperty.UnsetValue);
-                _hasProducedValue = false;
+                PublishValue(AvaloniaProperty.UnsetValue);
             }
         }
 
-        private void TemplatedParentChanged()
+        private void OnTemplatedParentChanged()
         {
-            if (_target?.TemplatedParent is { } templatedParent)
-            {
-                templatedParent.PropertyChanged += TemplatedParentPropertyChanged;
-            }
+            if (TryGetTemplatedParent(out var templatedParent))
+                templatedParent.PropertyChanged += OnTemplatedParentPropertyChanged;
 
             PublishValue();
         }
 
-        private void TargetPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+        private void OnTemplatedParentPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+        {
+            if (e.Property == Property)
+                PublishValue();
+        }
+
+        private void OnTargetPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
         {
             if (e.Property == StyledElement.TemplatedParentProperty)
             {
                 if (e.OldValue is AvaloniaObject oldValue)
-                {
-                    oldValue.PropertyChanged -= TemplatedParentPropertyChanged;
-                }
+                    oldValue.PropertyChanged -= OnTemplatedParentPropertyChanged;
 
-                TemplatedParentChanged();
+                OnTemplatedParentChanged();
             }
-        }
-
-        private void TemplatedParentPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
-        {
-            if (e.Property == Property)
+            else if (Mode is BindingMode.TwoWay or BindingMode.OneWayToSource && e.Property == TargetProperty)
             {
-                PublishValue();
+                WriteValueToSource(e.NewValue);
             }
         }
 
-        public IBinding ProvideValue() => this;
+        private bool TryGetTemplatedParent([NotNullWhen(true)] out AvaloniaObject? result)
+        {
+            if (TryGetTarget(out var target) &&
+                target is StyledElement targetElement &&
+                targetElement.TemplatedParent is { } templatedParent)
+            {
+                result = templatedParent;
+                return true;
+            }
+
+            result = null;
+            return false;
+        }
     }
 }
diff --git a/src/Avalonia.Base/Data/UpdateSourceTrigger.cs b/src/Avalonia.Base/Data/UpdateSourceTrigger.cs
new file mode 100644
index 000000000..846671b92
--- /dev/null
+++ b/src/Avalonia.Base/Data/UpdateSourceTrigger.cs
@@ -0,0 +1,29 @@
+namespace Avalonia.Data;
+
+/// <summary>
+/// Describes the timing of binding source updates.
+/// </summary>
+public enum UpdateSourceTrigger
+{
+    /// <summary>
+    /// The default <see cref="UpdateSourceTrigger"/> value of the binding target property.
+    /// This currently defaults to <see cref="PropertyChanged"/>.
+    /// </summary>
+    Default,
+
+    /// <summary>
+    /// Updates the binding source immediately whenever the binding target property changes.
+    /// </summary>
+    PropertyChanged,
+
+    /// <summary>
+    /// Updates the binding source whenever the binding target element loses focus.
+    /// </summary>
+    LostFocus,
+
+    /// <summary>
+    /// Updates the binding source only when you call the 
+    /// <see cref="BindingExpressionBase.UpdateSource()"/> method.
+    /// </summary>
+    Explicit,
+}
diff --git a/src/Avalonia.Base/Diagnostics/ObsoletionMessages.cs b/src/Avalonia.Base/Diagnostics/ObsoletionMessages.cs
new file mode 100644
index 000000000..bfada91ab
--- /dev/null
+++ b/src/Avalonia.Base/Diagnostics/ObsoletionMessages.cs
@@ -0,0 +1,12 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Avalonia.Diagnostics;
+
+internal static class ObsoletionMessages
+{
+    public const string MayBeRemovedInAvalonia12 = "This API may be removed in Avalonia 12. If you depend on this API, please open an issue with details of your use-case.";
+}
diff --git a/src/Avalonia.Base/DirectProperty.cs b/src/Avalonia.Base/DirectProperty.cs
index dd02553ea..ef1b67615 100644
--- a/src/Avalonia.Base/DirectProperty.cs
+++ b/src/Avalonia.Base/DirectProperty.cs
@@ -1,5 +1,4 @@
 using System;
-using System.Diagnostics.CodeAnalysis;
 using Avalonia.Data;
 
 namespace Avalonia
@@ -142,5 +141,11 @@ namespace Avalonia
 
             Setter((TOwner)instance, (TValue)value!);
         }
+
+        object? IDirectPropertyAccessor.GetUnsetValue(Type type)
+        {
+            var metadata = GetMetadata(type);
+            return metadata.UnsetValue;
+        }
     }
 }
diff --git a/src/Avalonia.Base/DirectPropertyBase.cs b/src/Avalonia.Base/DirectPropertyBase.cs
index 4dddc1279..64eb4d261 100644
--- a/src/Avalonia.Base/DirectPropertyBase.cs
+++ b/src/Avalonia.Base/DirectPropertyBase.cs
@@ -1,5 +1,6 @@
 using System;
 using Avalonia.Data;
+using Avalonia.Data.Core;
 using Avalonia.PropertyStore;
 
 namespace Avalonia
@@ -157,6 +158,12 @@ namespace Avalonia
             return null;
         }
 
+        internal override void RouteSetDirectValueUnchecked(AvaloniaObject o, object? value)
+        {
+            var bindingValue = BindingValue<TValue>.FromUntypedStrict(value);
+            o.SetDirectValueUnchecked<TValue>(this, bindingValue);
+        }
+
         internal override void RouteSetCurrentValue(AvaloniaObject o, object? value)
         {
             RouteSetValue(o, value, BindingPriority.LocalValue);
diff --git a/src/Avalonia.Base/IDirectPropertyAccessor.cs b/src/Avalonia.Base/IDirectPropertyAccessor.cs
index 016ca9a6f..f92ca1fbf 100644
--- a/src/Avalonia.Base/IDirectPropertyAccessor.cs
+++ b/src/Avalonia.Base/IDirectPropertyAccessor.cs
@@ -32,5 +32,11 @@ namespace Avalonia
         /// <param name="instance">The instance.</param>
         /// <param name="value">The value.</param>
         void SetValue(AvaloniaObject instance, object? value);
+
+        /// <summary>
+        /// Gets the unset value of the property for the specified type.
+        /// </summary>
+        /// <param name="type">The type.</param>
+        object? GetUnsetValue(Type type);
     }
 }
diff --git a/src/Avalonia.Base/Logging/TraceLogSink.cs b/src/Avalonia.Base/Logging/TraceLogSink.cs
index 1fee35bf2..a77b5d66d 100644
--- a/src/Avalonia.Base/Logging/TraceLogSink.cs
+++ b/src/Avalonia.Base/Logging/TraceLogSink.cs
@@ -80,15 +80,7 @@ namespace Avalonia.Logging
                 }
             }
 
-            if (source is object)
-            {
-                result.Append(" (");
-                result.Append(source.GetType().Name);
-                result.Append(" #");
-                result.Append(source.GetHashCode());
-                result.Append(')');
-            }
-
+            FormatSource(source, result);
             return StringBuilderCache.GetStringAndRelease(result);
         }
 
@@ -132,16 +124,25 @@ namespace Avalonia.Logging
                 }
             }
 
-            if (source is object)
-            {
-                result.Append('(');
-                result.Append(source.GetType().Name);
-                result.Append(" #");
-                result.Append(source.GetHashCode());
-                result.Append(')');
-            }
-
+            FormatSource(source, result);
             return StringBuilderCache.GetStringAndRelease(result);
         }
+
+        private static void FormatSource(object? source, StringBuilder result)
+        {
+            if (source is null)
+                return;
+
+            result.Append(" (");
+            result.Append(source.GetType().Name);
+            result.Append(" #");
+
+            if (source is StyledElement se && se.Name is not null)
+                result.Append(se.Name);
+            else
+                result.Append(source.GetHashCode());
+
+            result.Append(')');
+        }
     }
 }
diff --git a/src/Avalonia.Base/Properties/AssemblyInfo.cs b/src/Avalonia.Base/Properties/AssemblyInfo.cs
index d37ec86f2..f094fed1d 100644
--- a/src/Avalonia.Base/Properties/AssemblyInfo.cs
+++ b/src/Avalonia.Base/Properties/AssemblyInfo.cs
@@ -1,5 +1,6 @@
 using System.Reflection;
 using System.Runtime.CompilerServices;
+using Avalonia.Data;
 using Avalonia.Metadata;
 
 [assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia")]
@@ -33,3 +34,4 @@ using Avalonia.Metadata;
 [assembly: InternalsVisibleTo("Avalonia.Browser.Blazor, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c1bba1142285fe0419326fb25866ba62c47e6c2b5c1ab0c95b46413fad375471232cb81706932e1cef38781b9ebd39d5100401bacb651c6c5bbf59e571e81b3bc08d2a622004e08b1a6ece82a7e0b9857525c86d2b95fab4bc3dce148558d7f3ae61aa3a234086902aeface87d9dfdd32b9d2fe3c6dd4055b5ab4b104998bd87")]
 [assembly: InternalsVisibleTo("Avalonia.Browser, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c1bba1142285fe0419326fb25866ba62c47e6c2b5c1ab0c95b46413fad375471232cb81706932e1cef38781b9ebd39d5100401bacb651c6c5bbf59e571e81b3bc08d2a622004e08b1a6ece82a7e0b9857525c86d2b95fab4bc3dce148558d7f3ae61aa3a234086902aeface87d9dfdd32b9d2fe3c6dd4055b5ab4b104998bd87")]
 [assembly: InternalsVisibleTo("DynamicProxyGenAssembly2, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c547cac37abd99c8db225ef2f6c8a3602f3b3606cc9891605d02baa56104f4cfc0734aa39b93bf7852f7d9266654753cc297e7d2edfe0bac1cdcf9f717241550e0a7b191195b7667bb4f64bcb8e2121380fd1d9d46ad2d92d2d15605093924cceaf74c4861eff62abf69b9291ed0a340e113be11e6a7d3113e92484cf7045cc7")]
+
diff --git a/src/Avalonia.Base/PropertyStore/BindingEntryBase.cs b/src/Avalonia.Base/PropertyStore/BindingEntryBase.cs
index ef4372053..dc2f19d38 100644
--- a/src/Avalonia.Base/PropertyStore/BindingEntryBase.cs
+++ b/src/Avalonia.Base/PropertyStore/BindingEntryBase.cs
@@ -139,8 +139,6 @@ namespace Avalonia.PropertyStore
                 var property = instance.Property;
                 var originalType = value.Type;
 
-                LoggingUtils.LogIfNecessary(owner, property, value);
-
                 if (!value.HasValue && value.Type != BindingValueType.DataValidationError)
                     value = value.WithValue(instance.GetCachedDefaultValue());
 
diff --git a/src/Avalonia.Base/PropertyStore/EffectiveValue.cs b/src/Avalonia.Base/PropertyStore/EffectiveValue.cs
index a00a51e69..da7bec836 100644
--- a/src/Avalonia.Base/PropertyStore/EffectiveValue.cs
+++ b/src/Avalonia.Base/PropertyStore/EffectiveValue.cs
@@ -127,6 +127,18 @@ namespace Avalonia.PropertyStore
             IValueEntry value,
             BindingPriority priority);
 
+        /// <summary>
+        /// Sets the value and base value for a LocalValue priority, raising 
+        /// <see cref="AvaloniaObject.PropertyChanged"/> where necessary.
+        /// </summary>
+        /// <param name="owner">The associated value store.</param>
+        /// <param name="property">The property being changed.</param>
+        /// <param name="value">The new value of the property.</param>
+        public abstract void SetLocalValueAndRaise(
+            ValueStore owner,
+            AvaloniaProperty property,
+            object? value);
+
         /// <summary>
         /// Raises <see cref="AvaloniaObject.PropertyChanged"/> in response to an inherited value
         /// change.
diff --git a/src/Avalonia.Base/PropertyStore/EffectiveValue`1.cs b/src/Avalonia.Base/PropertyStore/EffectiveValue`1.cs
index 832a56ad1..3216273b8 100644
--- a/src/Avalonia.Base/PropertyStore/EffectiveValue`1.cs
+++ b/src/Avalonia.Base/PropertyStore/EffectiveValue`1.cs
@@ -66,6 +66,14 @@ namespace Avalonia.PropertyStore
             }
         }
 
+        public override void SetLocalValueAndRaise(
+            ValueStore owner,
+            AvaloniaProperty property,
+            object? value)
+        {
+            SetLocalValueAndRaise(owner, (StyledProperty<T>)property, (T)value!);
+        }
+
         public void SetLocalValueAndRaise(
             ValueStore owner,
             StyledProperty<T> property,
@@ -138,6 +146,10 @@ namespace Avalonia.PropertyStore
 
         public override void DisposeAndRaiseUnset(ValueStore owner, AvaloniaProperty property)
         {
+            var clearDataValidation = ValueEntry?.GetDataValidationState(out _, out _) ??
+                BaseValueEntry?.GetDataValidationState(out _, out _) ??
+                false;
+
             ValueEntry?.Unsubscribe();
             BaseValueEntry?.Unsubscribe();
 
@@ -163,12 +175,8 @@ namespace Avalonia.PropertyStore
                     owner.OnInheritedEffectiveValueDisposed(p, Value, newValue);
             }
 
-            if (ValueEntry?.GetDataValidationState(out _, out _) ??
-                BaseValueEntry?.GetDataValidationState(out _, out _) ??
-                false)
-            {
+            if (clearDataValidation)
                 owner.Owner.OnUpdateDataValidation(p, BindingValueType.UnsetValue, null);
-            }
         }
 
         protected override void CoerceDefaultValueAndRaise(ValueStore owner, AvaloniaProperty property)
diff --git a/src/Avalonia.Base/PropertyStore/ImmediateValueFrame.cs b/src/Avalonia.Base/PropertyStore/ImmediateValueFrame.cs
index 222d857aa..600be5437 100644
--- a/src/Avalonia.Base/PropertyStore/ImmediateValueFrame.cs
+++ b/src/Avalonia.Base/PropertyStore/ImmediateValueFrame.cs
@@ -1,5 +1,6 @@
 using System;
 using Avalonia.Data;
+using Avalonia.Data.Core;
 
 namespace Avalonia.PropertyStore
 {
@@ -14,6 +15,12 @@ namespace Avalonia.PropertyStore
         {
         }
 
+        public IValueEntry AddBinding(UntypedBindingExpressionBase source)
+        {
+            Add(source);
+            return source;
+        }
+
         public TypedBindingEntry<T> AddBinding<T>(
             StyledProperty<T> property,
             IObservable<BindingValue<T>> source)
diff --git a/src/Avalonia.Base/PropertyStore/LocalValueBindingObserverBase.cs b/src/Avalonia.Base/PropertyStore/LocalValueBindingObserverBase.cs
index 5d920cf88..084ac7011 100644
--- a/src/Avalonia.Base/PropertyStore/LocalValueBindingObserverBase.cs
+++ b/src/Avalonia.Base/PropertyStore/LocalValueBindingObserverBase.cs
@@ -88,8 +88,6 @@ namespace Avalonia.PropertyStore
                 var property = instance.Property;
                 var originalType = value.Type;
 
-                LoggingUtils.LogIfNecessary(owner.Owner, property, value);
-
                 // Revert to the default value if the binding value fails validation, or if
                 // there was no value (though not if there was a data validation error).
                 if ((value.HasValue && property.ValidateValue?.Invoke(value.Value) == false) ||
diff --git a/src/Avalonia.Base/PropertyStore/LoggingUtils.cs b/src/Avalonia.Base/PropertyStore/LoggingUtils.cs
deleted file mode 100644
index 8b3015eca..000000000
--- a/src/Avalonia.Base/PropertyStore/LoggingUtils.cs
+++ /dev/null
@@ -1,82 +0,0 @@
-using System;
-using System.Reflection;
-using System.Runtime.CompilerServices;
-using Avalonia.Data;
-
-namespace Avalonia.PropertyStore
-{
-    internal static class LoggingUtils
-    {
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void LogIfNecessary(
-            AvaloniaObject owner,
-            AvaloniaProperty property,
-            BindingNotification value)
-        {
-            if (value.ErrorType != BindingErrorType.None)
-                Log(owner, property, value.Error!);
-        }
-
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void LogIfNecessary<T>(
-            AvaloniaObject owner,
-            AvaloniaProperty property,
-            BindingValue<T> value)
-        {
-            if (value.HasError)
-                Log(owner, property, value.Error!);
-        }
-
-        public static void LogInvalidValue(
-            AvaloniaObject owner,
-            AvaloniaProperty property,
-            Type expectedType,
-            object? value)
-        {
-            if (value is not null)
-            {
-                owner.GetBindingWarningLogger(property, null)?.Log(
-                    owner,
-                    "Error in binding to {Target}.{Property}: expected {ExpectedType}, got {Value} ({ValueType})",
-                    owner,
-                    property,
-                    expectedType,
-                    value,
-                    value.GetType());
-            }
-            else
-            {
-                owner.GetBindingWarningLogger(property, null)?.Log(
-                    owner,
-                    "Error in binding to {Target}.{Property}: expected {ExpectedType}, got null",
-                    owner,
-                    property,
-                    expectedType);
-            }
-        }
-
-        private static void Log(
-            AvaloniaObject owner,
-            AvaloniaProperty property,
-            Exception e)
-        {
-            if (e is TargetInvocationException t)
-                e = t.InnerException!;
-
-            if (e is AggregateException a)
-            {
-                foreach (var i in a.InnerExceptions)
-                    Log(owner, property, i);
-            }
-            else
-            {
-                owner.GetBindingWarningLogger(property, e)?.Log(
-                    owner,
-                    "Error in binding to {Target}.{Property}: {Message}",
-                    owner,
-                    property,
-                    e.Message);
-            }
-        }
-    }
-}
diff --git a/src/Avalonia.Base/PropertyStore/UntypedBindingEntry.cs b/src/Avalonia.Base/PropertyStore/UntypedBindingEntry.cs
deleted file mode 100644
index e3a760747..000000000
--- a/src/Avalonia.Base/PropertyStore/UntypedBindingEntry.cs
+++ /dev/null
@@ -1,39 +0,0 @@
-using System;
-using Avalonia.Data;
-
-namespace Avalonia.PropertyStore
-{
-    /// <summary>
-    /// An <see cref="IValueEntry"/> that holds a binding whose source observable and target
-    /// property are both untyped.
-    /// </summary>
-    internal class UntypedBindingEntry : BindingEntryBase<object?, object?>
-    {
-        private readonly Func<object?, bool>? _validate;
-
-        public UntypedBindingEntry(
-            AvaloniaObject target,
-            ValueFrame frame,
-            AvaloniaProperty property,
-            IObservable<object?> source)
-            : base(target, frame, property, source)
-        {
-            _validate = ((IStyledPropertyAccessor)property).ValidateValue;
-        }
-
-        protected override BindingValue<object?> ConvertAndValidate(object? value)
-        {
-            return UntypedValueUtils.ConvertAndValidate(value, Property.PropertyType, _validate);
-        }
-
-        protected override BindingValue<object?> ConvertAndValidate(BindingValue<object?> value)
-        {
-            throw new NotSupportedException();
-        }
-
-        protected override object? GetDefaultValue(Type ownerType)
-        {
-            return ((IStyledPropertyMetadata)Property.GetMetadata(ownerType)).DefaultValue;
-        }
-    }
-}
diff --git a/src/Avalonia.Base/PropertyStore/UntypedValueUtils.cs b/src/Avalonia.Base/PropertyStore/UntypedValueUtils.cs
index 4912ec1d8..fb22e4679 100644
--- a/src/Avalonia.Base/PropertyStore/UntypedValueUtils.cs
+++ b/src/Avalonia.Base/PropertyStore/UntypedValueUtils.cs
@@ -23,23 +23,5 @@ namespace Avalonia.PropertyStore
 
             return v;
         }
-
-        [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = TrimmingMessages.ImplicitTypeConversionSupressWarningMessage)]
-        public static bool TryConvertAndValidate<T>(
-            StyledProperty<T> property,
-            object? value, 
-            [MaybeNullWhen(false)] out T result)
-        {
-            if (TypeUtilities.TryConvertImplicit(typeof(T), value, out var v))
-            {
-                result = (T)v!;
-
-                if (property.ValidateValue?.Invoke(result) != false)
-                    return true;
-            }
-
-            result = default;
-            return false;
-        }
     }
 }
diff --git a/src/Avalonia.Base/PropertyStore/ValueFrame.cs b/src/Avalonia.Base/PropertyStore/ValueFrame.cs
index 8ef68c651..0b51189a1 100644
--- a/src/Avalonia.Base/PropertyStore/ValueFrame.cs
+++ b/src/Avalonia.Base/PropertyStore/ValueFrame.cs
@@ -2,6 +2,7 @@
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using Avalonia.Data;
+using Avalonia.Data.Core;
 using Avalonia.Utilities;
 
 namespace Avalonia.PropertyStore
diff --git a/src/Avalonia.Base/PropertyStore/ValueStore.cs b/src/Avalonia.Base/PropertyStore/ValueStore.cs
index 85adee238..2cd1ac98e 100644
--- a/src/Avalonia.Base/PropertyStore/ValueStore.cs
+++ b/src/Avalonia.Base/PropertyStore/ValueStore.cs
@@ -4,13 +4,15 @@ using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using Avalonia.Data;
+using Avalonia.Data.Core;
 using Avalonia.Diagnostics;
 using Avalonia.Styling;
+using Avalonia.Threading;
 using Avalonia.Utilities;
 
 namespace Avalonia.PropertyStore
 {
-    internal class ValueStore
+    internal class ValueStore : IBindingExpressionSink
     {
         private readonly List<ValueFrame> _frames = new();
         private Dictionary<int, IDisposable>? _localValueBindings;
@@ -41,6 +43,46 @@ namespace Avalonia.PropertyStore
             ReevaluateEffectiveValues();
         }
 
+        public BindingExpressionBase AddBinding(
+            AvaloniaProperty property,
+            UntypedBindingExpressionBase source)
+        {
+            if (property.IsDirect)
+            {
+                DisposeExistingLocalValueBinding(property);
+                _localValueBindings ??= new();
+                _localValueBindings[property.Id] = source;
+                source.AttachAndStart(this, Owner, property, BindingPriority.LocalValue);
+                return source;
+            }
+            else
+            {
+                var priority = source.Priority;
+
+                if (priority == BindingPriority.LocalValue)
+                {
+                    DisposeExistingLocalValueBinding(property);
+                    _localValueBindings ??= new();
+                    _localValueBindings[property.Id] = source;
+                    source.AttachAndStart(this, Owner, property, priority);
+                    return source;
+                }
+                else
+                {
+                    var effective = GetEffectiveValue(property);
+                    var frame = GetOrCreateImmediateValueFrame(property, priority, out _);
+
+                    source.Attach(this, frame, Owner, property, priority);
+                    frame.AddBinding(source);
+
+                    if (effective is null || priority <= effective.Priority)
+                        source.Start();
+
+                    return source;
+                }
+            }
+        }
+
         public IDisposable AddBinding<T>(
             StyledProperty<T> property,
             IObservable<BindingValue<T>> source,
@@ -212,6 +254,20 @@ namespace Avalonia.PropertyStore
             }
         }
 
+        public void SetLocalValue(AvaloniaProperty property, object? value)
+        {
+            if (TryGetEffectiveValue(property, out var existing))
+            {
+                existing.SetLocalValueAndRaise(this, property, value);
+            }
+            else
+            {
+                var effectiveValue = property.CreateEffectiveValue(Owner);
+                AddEffectiveValue(property, effectiveValue);
+                effectiveValue.SetLocalValueAndRaise(this, property, value);
+            }
+        }
+
         public void SetLocalValue<T>(StyledProperty<T> property, T value)
         {
             if (TryGetEffectiveValue(property, out var existing))
@@ -405,6 +461,7 @@ namespace Avalonia.PropertyStore
         /// </summary>
         /// <param name="entry">The binding entry.</param>
         /// <param name="priority">The priority of binding which produced a new value.</param>
+        [Obsolete("TODO: Remove?")]
         public void OnBindingValueChanged(
             IValueEntry entry,
             BindingPriority priority)
@@ -528,6 +585,7 @@ namespace Avalonia.PropertyStore
         /// </summary>
         /// <param name="property">The previously bound property.</param>
         /// <param name="observer">The observer.</param>
+        [Obsolete("TODO: Remove?")]
         public void OnLocalValueBindingCompleted(AvaloniaProperty property, IDisposable observer)
         {
             if (_localValueBindings is not null &&
@@ -689,6 +747,88 @@ namespace Avalonia.PropertyStore
                 overridden);
         }
 
+        void IBindingExpressionSink.OnChanged(
+            UntypedBindingExpressionBase instance,
+            bool hasValueChanged,
+            bool hasErrorChanged,
+            object? value,
+            BindingError? error)
+        {
+            Dispatcher.UIThread.VerifyAccess();
+            Debug.Assert(instance.TargetProperty is not null);
+
+            var property = instance.TargetProperty;
+
+            if (property.IsDirect)
+            {
+                if (hasValueChanged)
+                    property.RouteSetDirectValueUnchecked(Owner, value);
+            }
+            else
+            {
+                var priority = instance.Priority;
+
+                if (hasValueChanged)
+                {
+                    if (priority == BindingPriority.LocalValue)
+                    {
+                        if (value != AvaloniaProperty.UnsetValue)
+                            SetLocalValue(property, value);
+                        else if (property == StyledElement.DataContextProperty)
+                            SetLocalValue(property, null);
+                        else
+                            ClearValue(property);
+                    }
+                    else
+                    {
+                        if (TryGetEffectiveValue(property, out var existing))
+                        {
+                            if (priority <= existing.BasePriority)
+                                ReevaluateEffectiveValue(property, existing, changedValueEntry: instance);
+                        }
+                        else
+                        {
+                            AddEffectiveValueAndRaise(property, instance, priority);
+                        }
+                    }
+                }
+            }
+
+            if (hasErrorChanged && instance.IsDataValidationEnabled)
+            {
+                var e = error?.ErrorType.ToBindingValueType() ?? BindingValueType.Value;
+                Owner.OnUpdateDataValidation(property, e, error?.Exception);
+            }
+        }
+
+        /// <summary>
+        /// Called by a binding expression when the binding produces completes.
+        /// </summary>
+        /// <param name="instance">The binding expression.</param>
+        void IBindingExpressionSink.OnCompleted(UntypedBindingExpressionBase instance)
+        {
+            Dispatcher.UIThread.VerifyAccess();
+            Debug.Assert(instance.TargetProperty is not null);
+
+            var property = instance.TargetProperty;
+
+            if (instance.IsDataValidationEnabled)
+                Owner.OnUpdateDataValidation(property, BindingValueType.UnsetValue, null);
+            
+            if (instance.Priority == BindingPriority.LocalValue)
+            {
+                if (_localValueBindings is not null &&
+                    _localValueBindings.TryGetValue(property.Id, out var existing))
+                {
+                    if (existing == instance)
+                    {
+                        _localValueBindings?.Remove(property.Id);
+                        ClearValue(property);
+                    }
+                }
+            }
+        }
+
         private int InsertFrame(ValueFrame frame)
         {
             Debug.Assert(!_frames.Contains(frame));
diff --git a/src/Avalonia.Base/StyledProperty.cs b/src/Avalonia.Base/StyledProperty.cs
index b6bd73723..df12b7099 100644
--- a/src/Avalonia.Base/StyledProperty.cs
+++ b/src/Avalonia.Base/StyledProperty.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Diagnostics.CodeAnalysis;
 using Avalonia.Data;
+using Avalonia.Data.Core;
 using Avalonia.PropertyStore;
 using Avalonia.Utilities;
 
@@ -160,10 +161,16 @@ namespace Avalonia
 
         bool IStyledPropertyAccessor.ValidateValue(object? value)
         {
-            if (value is null && !typeof(TValue).IsValueType)
-                return ValidateValue?.Invoke(default!) ?? true;
-            if (value is TValue typed)
+            if (value is null)
+            {
+                if (!typeof(TValue).IsValueType || Nullable.GetUnderlyingType(typeof(TValue)) != null)
+                    return ValidateValue?.Invoke(default!) ?? true;
+            }
+            else if (value is TValue typed)
+            {
                 return ValidateValue?.Invoke(typed) ?? true;
+            }
+
             return false;
         }
 
diff --git a/src/Avalonia.Base/Styling/PropertySetterBindingInstance.cs b/src/Avalonia.Base/Styling/PropertySetterBindingInstance.cs
deleted file mode 100644
index be5a99977..000000000
--- a/src/Avalonia.Base/Styling/PropertySetterBindingInstance.cs
+++ /dev/null
@@ -1,60 +0,0 @@
-using System;
-using Avalonia.Data;
-using Avalonia.PropertyStore;
-
-namespace Avalonia.Styling
-{
-    internal class PropertySetterBindingInstance : UntypedBindingEntry, ISetterInstance
-    {
-        private readonly AvaloniaObject _target;
-        private readonly BindingMode _mode;
-
-        public PropertySetterBindingInstance(
-            AvaloniaObject target,
-            StyleInstance instance,
-            AvaloniaProperty property,
-            BindingMode mode,
-            IObservable<object?> source)
-            : base(target, instance, property, source)
-        {
-            _target = target;
-            _mode = mode;
-
-            if (mode == BindingMode.TwoWay &&
-                source is not IObserver<object?>)
-            {
-                throw new NotSupportedException(
-                    "Attempting to bind two-way with a binding source which doesn't support it.");
-            }
-        }
-
-        public override void Unsubscribe()
-        {
-            _target.PropertyChanged -= PropertyChanged;
-            base.Unsubscribe();
-        }
-
-        protected override void Start(bool produceValue)
-        {
-            if (!IsSubscribed)
-            {
-                if (_mode == BindingMode.TwoWay)
-                {
-                    var observer = (IObserver<object?>)Source;
-                    _target.PropertyChanged += PropertyChanged;
-                }
-
-                base.Start(produceValue);
-            }
-        }
-
-        private void PropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
-        {
-            if (e.Property == Property && e.Priority >= BindingPriority.LocalValue)
-            {
-                if (Frame.Owner is not null && !Frame.Owner.IsEvaluating)
-                    ((IObserver<object?>)Source).OnNext(e.NewValue);
-            }
-        }
-    }
-}
diff --git a/src/Avalonia.Base/Styling/Setter.cs b/src/Avalonia.Base/Styling/Setter.cs
index f31394d6f..98efff55e 100644
--- a/src/Avalonia.Base/Styling/Setter.cs
+++ b/src/Avalonia.Base/Styling/Setter.cs
@@ -2,6 +2,7 @@ using System;
 using System.Diagnostics.CodeAnalysis;
 using Avalonia.Animation;
 using Avalonia.Data;
+using Avalonia.Data.Core;
 using Avalonia.Metadata;
 using Avalonia.PropertyStore;
 
@@ -75,8 +76,10 @@ namespace Avalonia.Styling
                 throw new InvalidOperationException(
                     $"Cannot set direct property '{Property}' in '{instance.Source}' because the style has an activator.");
 
-            if (Value is IBinding binding)
+            if (Value is IBinding2 binding)
                 return SetBinding((StyleInstance)instance, ao, binding);
+            else if (Value is IBinding)
+                throw new AvaloniaInternalException("TODO: Make all IBindings implement IBinding2.");
             else if (Value is ITemplate template && !typeof(ITemplate).IsAssignableFrom(Property.PropertyType))
                 return new PropertySetterTemplateInstance(Property, template);
             else if (!Property.IsValidValue(Value))
@@ -102,25 +105,13 @@ namespace Avalonia.Styling
             return Property ?? throw new InvalidOperationException("Setter.Property must be set.");
         }
 
-        private ISetterInstance SetBinding(StyleInstance instance, AvaloniaObject target, IBinding binding)
+        private ISetterInstance SetBinding(StyleInstance instance, AvaloniaObject target, IBinding2 binding)
         {
             if (!Property!.IsDirect)
             {
-                var hasDataValidation = Property.GetMetadata(target.GetType()).EnableDataValidation ?? false;
-                var i = binding.Initiate(target, Property, enableDataValidation: hasDataValidation)!;
-                var mode = i.Mode;
-
-                if (mode == BindingMode.Default)
-                {
-                    mode = Property!.GetMetadata(target.GetType()).DefaultBindingMode;
-                }
-
-                if (mode == BindingMode.OneWay || mode == BindingMode.TwoWay)
-                {
-                    return new PropertySetterBindingInstance(target, instance, Property, mode, i.Source);
-                }
-
-                throw new NotSupportedException();
+                var expression = binding.Instance(target, Property, null);
+                expression.Attach(target.GetValueStore(), null, target, Property, instance.Priority);
+                return expression;
             }
             else
             {
diff --git a/src/Avalonia.Base/Utilities/TypeUtilities.cs b/src/Avalonia.Base/Utilities/TypeUtilities.cs
index 7dbb0872f..128e2a546 100644
--- a/src/Avalonia.Base/Utilities/TypeUtilities.cs
+++ b/src/Avalonia.Base/Utilities/TypeUtilities.cs
@@ -129,6 +129,12 @@ namespace Avalonia.Utilities
         [RequiresUnreferencedCode(TrimmingMessages.TypeConversionRequiresUnreferencedCodeMessage)]
         public static bool TryConvert(Type to, object? value, CultureInfo? culture, out object? result)
         {
+            if (to == typeof(object))
+            {
+                result = value;
+                return true;
+            }
+
             if (value == null)
             {
                 result = null;
@@ -382,7 +388,7 @@ namespace Avalonia.Utilities
         }
 
         [Flags]
-        private enum OperatorType
+        internal enum OperatorType
         {
             Implicit = 1,
             Explicit = 2
@@ -393,7 +399,7 @@ namespace Avalonia.Utilities
             return type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>);
         }
 
-        private static MethodInfo? FindTypeConversionOperatorMethod(
+        internal static MethodInfo? FindTypeConversionOperatorMethod(
             [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods)] Type fromType,
             Type toType, OperatorType operatorType)
         {
@@ -423,5 +429,25 @@ namespace Avalonia.Utilities
 
             return null;
         }
+
+        /// <summary>
+        /// Determines whether the specified object instances are "identity" equal which means
+        /// reference equal for reference types and <see cref="object.Equals(object?)"/> for value
+        /// types.
+        /// </summary>
+        /// <param name="a">The first object to compare.</param>
+        /// <param name="b">The second object to compare.</param>
+        /// <param name="type">
+        /// The type which determines whether the objects should be treated as a reference or
+        /// value type.
+        /// </param>
+        /// <returns>True if the objects are considered equal; otherwise false.</returns>
+        internal static bool IdentityEquals(object? a, object? b, Type type)
+        {
+            if (type.IsValueType || type == typeof(string))
+                return Equals(a, b);
+            else
+                return ReferenceEquals(a, b);
+        }
     }
 }
diff --git a/src/Avalonia.Base/Visual.cs b/src/Avalonia.Base/Visual.cs
index 85dc082ff..9d6054c3d 100644
--- a/src/Avalonia.Base/Visual.cs
+++ b/src/Avalonia.Base/Visual.cs
@@ -589,26 +589,6 @@ namespace Avalonia
             RaisePropertyChanged(VisualParentProperty, oldParent, newParent);
         }
 
-        internal override ParametrizedLogger? GetBindingWarningLogger(
-            AvaloniaProperty property,
-            Exception? e)
-        {
-            // Don't log a binding error unless the control is attached to the logical tree.
-            if (!((ILogical)this).IsAttachedToLogicalTree)
-                return null;
-
-            if (e is BindingChainException b &&
-                string.IsNullOrEmpty(b.ExpressionErrorPoint) &&
-                DataContext == null)
-            {
-                // The error occurred at the root of the binding chain and DataContext is null;
-                // don't log this - the DataContext probably hasn't been set up yet.
-                return null;
-            }
-
-            return Logger.TryGet(LogEventLevel.Warning, LogArea.Binding);
-        }
-
         /// <summary>
         /// Called when a visual's <see cref="RenderTransform"/> changes.
         /// </summary>
diff --git a/src/Avalonia.Controls/AutoCompleteBox/AutoCompleteBox.cs b/src/Avalonia.Controls/AutoCompleteBox/AutoCompleteBox.cs
index 54af9fb74..7f1253e80 100644
--- a/src/Avalonia.Controls/AutoCompleteBox/AutoCompleteBox.cs
+++ b/src/Avalonia.Controls/AutoCompleteBox/AutoCompleteBox.cs
@@ -2094,7 +2094,7 @@ namespace Avalonia.Controls
                 {
                     _binding = value;
                     if (value is not null)
-                        AvaloniaObjectExtensions.Bind(this, ValueProperty, value);
+                        Bind(ValueProperty, value);
                 }
             }
 
diff --git a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/XamlIlBindingPathHelper.cs b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/XamlIlBindingPathHelper.cs
index 965d6cb98..a4fb79c85 100644
--- a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/XamlIlBindingPathHelper.cs
+++ b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/XamlIlBindingPathHelper.cs
@@ -15,6 +15,7 @@ using XamlX.IL;
 using Avalonia.Utilities;
 
 using XamlIlEmitContext = XamlX.Emit.XamlEmitContextWithLocals<XamlX.IL.IXamlILEmitter, XamlX.IL.XamlILNodeEmitResult>;
+using System.Xml.Linq;
 
 namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions
 {
@@ -245,12 +246,18 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions
                         nodes.Add(new FindVisualAncestorPathElementNode(visualAncestor.Type, visualAncestor.Level));
                         break;
                     case TemplatedParentBindingExpressionNode templatedParent:
-                        var templatedParentField = context.GetAvaloniaTypes().StyledElement.GetAllFields()
-                            .FirstOrDefault(f => f.IsStatic && f.IsPublic && f.Name == "TemplatedParentProperty");
-                        nodes.Add(new SelfPathElementNode(selfType));
-                        nodes.Add(new XamlIlAvaloniaPropertyPropertyPathElementNode(
-                            templatedParentField,
-                            templatedParent.Type));
+                        var templatedParentType = context
+                            .ParentNodes()
+                            .OfType<AvaloniaXamlIlTargetTypeMetadataNode>()
+                            .Where(x => x.ScopeType == AvaloniaXamlIlTargetTypeMetadataNode.ScopeTypes.ControlTemplate)
+                            .FirstOrDefault()?.TargetType;
+
+                        if (templatedParentType is null)
+                        {
+                            throw new XamlTransformException("A binding with a TemplatedParent RelativeSource has to be in a ControlTemplate.", lineInfo);
+                        }
+
+                        nodes.Add(new TemplatedParentPathElementNode(templatedParentType.GetClrType()));
                         break;
                     case BindingExpressionGrammar.AncestorNode ancestor:
                         if (ancestor.Namespace is null && ancestor.TypeName is null)
@@ -557,6 +564,22 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions
             }
         }
 
+        class TemplatedParentPathElementNode : IXamlIlBindingPathElementNode
+        {
+            public TemplatedParentPathElementNode(IXamlType elementType)
+            {
+                Type = elementType;
+            }
+
+            public IXamlType Type { get; }
+
+            public void Emit(XamlIlEmitContext context, IXamlILEmitter codeGen)
+            {
+                codeGen
+                    .EmitCall(context.GetAvaloniaTypes().CompiledBindingPathBuilder.FindMethod(m => m.Name == "TemplatedParent"));
+            }
+        }
+
         class XamlIlAvaloniaPropertyPropertyPathElementNode : IXamlIlBindingPathElementNode
         {
             private readonly IXamlField _field;
@@ -876,8 +899,14 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions
 
             public XamlILNodeEmitResult Emit(XamlIlEmitContext context, IXamlILEmitter codeGen)
             {
+                var intType = context.Configuration.TypeSystem.GetType("System.Int32");
                 var types = context.GetAvaloniaTypes();
-                codeGen.Newobj(types.CompiledBindingPathBuilder.FindConstructor());
+
+                // We're calling the CompiledBindingPathBuilder(int apiVersion) with an apiVersion 
+                // of 1 to indicate that we don't want TemplatedParent compatibility hacks enabled.
+                codeGen
+                    .Ldc_I4(1)
+                    .Newobj(types.CompiledBindingPathBuilder.FindConstructor(new() { intType }));
 
                 foreach (var transform in _transformElements)
                 {
diff --git a/src/Markup/Avalonia.Markup.Xaml/Avalonia.Markup.Xaml.csproj b/src/Markup/Avalonia.Markup.Xaml/Avalonia.Markup.Xaml.csproj
index ff62081da..ec4e79aa2 100644
--- a/src/Markup/Avalonia.Markup.Xaml/Avalonia.Markup.Xaml.csproj
+++ b/src/Markup/Avalonia.Markup.Xaml/Avalonia.Markup.Xaml.csproj
@@ -8,58 +8,52 @@
     <EnableDefaultItems>false</EnableDefaultItems>
     <NoWarn>$(NoWarn);CS1591</NoWarn>
   </PropertyGroup>
-    <ItemGroup>
-      <Compile Include="AvaloniaXamlLoader.cs" />
-      <Compile Include="Converters\AvaloniaUriTypeConverter.cs" />
-      <Compile Include="Converters\ColorToBrushConverter.cs" />
-      <Compile Include="Converters\FontFamilyTypeConverter.cs" />
-      <Compile Include="Converters\TimeSpanTypeConverter.cs" />
-      <Compile Include="Extensions.cs" />
-      <Compile Include="MarkupExtension.cs" />
-      <Compile Include="MarkupExtensions\CompiledBindingExtension.cs" />
-      <Compile Include="MarkupExtensions\CompiledBindings\ArrayElementPlugin.cs" />
-      <Compile Include="MarkupExtensions\CompiledBindings\CommandAccessorPlugin.cs" />
-      <Compile Include="MarkupExtensions\CompiledBindings\CompiledBindingPath.cs" />
-      <Compile Include="MarkupExtensions\CompiledBindings\FindVisualAncestorNode.cs" />
-      <Compile Include="MarkupExtensions\CompiledBindings\MethodAccessorPlugin.cs" />
-      <Compile Include="MarkupExtensions\CompiledBindings\ObservableStreamPlugin.cs" />
-      <Compile Include="MarkupExtensions\CompiledBindings\PropertyInfoAccessorFactory.cs" />
-      <Compile Include="MarkupExtensions\CompiledBindings\PropertyInfoAccessorPlugin.cs" />
-      <Compile Include="MarkupExtensions\CompiledBindings\StrongTypeCastNode.cs" />
-      <Compile Include="MarkupExtensions\CompiledBindings\TaskStreamPlugin.cs" />
-      <Compile Include="MarkupExtensions\DynamicResourceExtension.cs" />
-      <Compile Include="MarkupExtensions\On.cs" />
-      <Compile Include="MarkupExtensions\OnFormFactorExtension.cs" />
-      <Compile Include="MarkupExtensions\OnPlatformExtension.cs" />
-      <Compile Include="MarkupExtensions\ResolveByNameExtension.cs" />
-      <Compile Include="MarkupExtensions\StaticResourceExtension.cs" />
-      <Compile Include="Parsers\PropertyParser.cs" />
-      <Compile Include="Converters\BitmapTypeConverter.cs" />
-      <Compile Include="Converters\IconTypeConverter.cs" />
-      <Compile Include="Converters\AvaloniaPropertyTypeConverter.cs" />
-      <Compile Include="Converters\PointsListTypeConverter.cs" />
-      <Compile Include="MarkupExtensions\ReflectionBindingExtension.cs" />
-      <Compile Include="MarkupExtensions\RelativeSourceExtension.cs" />
-      <Compile Include="Properties\AssemblyInfo.cs" />
-      <Compile Include="RuntimeXamlLoaderConfiguration.cs" />
-      <Compile Include="RuntimeXamlLoaderDocument.cs" />
-      <Compile Include="Styling\MergeResourceInclude.cs" />
-      <Compile Include="Styling\ResourceInclude.cs" />
-      <Compile Include="Styling\StyleInclude.cs" />
-      <Compile Include="Templates\ControlTemplate.cs" />
-      <Compile Include="Templates\DataTemplate.cs" />
-      <Compile Include="Templates\FocusAdornerTemplate.cs" />
-      <Compile Include="Templates\ItemsPanelTemplate.cs" />
-      <Compile Include="Templates\Template.cs" />
-      <Compile Include="Templates\TemplateContent.cs" />
-      <Compile Include="Templates\TreeDataTemplate.cs" />
-      <Compile Include="XamlIl\Runtime\IAvaloniaXamlIlControlTemplateProvider.cs" />
-      <Compile Include="XamlIl\Runtime\IAvaloniaXamlIlParentStackProvider.cs" />
-      <Compile Include="XamlIl\Runtime\IAvaloniaXamlIlXmlNamespaceInfoProviderV1.cs" />
-      <Compile Include="XamlIl\Runtime\XamlIlRuntimeHelpers.cs" />
-      <Compile Include="XamlLoadException.cs" />
-      <Compile Include="XamlTypes.cs" />
-    </ItemGroup>
+  <ItemGroup>
+    <Compile Include="AvaloniaXamlLoader.cs" />
+    <Compile Include="Converters\AvaloniaUriTypeConverter.cs" />
+    <Compile Include="Converters\ColorToBrushConverter.cs" />
+    <Compile Include="Converters\FontFamilyTypeConverter.cs" />
+    <Compile Include="Converters\TimeSpanTypeConverter.cs" />
+    <Compile Include="Data\DynamicResourceExpression.cs" />
+    <Compile Include="Extensions.cs" />
+    <Compile Include="MarkupExtension.cs" />
+    <Compile Include="MarkupExtensions\CompiledBindingExtension.cs" />
+    <Compile Include="MarkupExtensions\CompiledBindings\CompiledBindingPath.cs" />
+    <Compile Include="MarkupExtensions\CompiledBindings\PropertyInfoAccessorFactory.cs" />
+    <Compile Include="MarkupExtensions\CompiledBindings\TaskStreamPlugin.cs" />
+    <Compile Include="MarkupExtensions\DynamicResourceExtension.cs" />
+    <Compile Include="MarkupExtensions\On.cs" />
+    <Compile Include="MarkupExtensions\OnFormFactorExtension.cs" />
+    <Compile Include="MarkupExtensions\OnPlatformExtension.cs" />
+    <Compile Include="MarkupExtensions\ResolveByNameExtension.cs" />
+    <Compile Include="MarkupExtensions\StaticResourceExtension.cs" />
+    <Compile Include="Parsers\PropertyParser.cs" />
+    <Compile Include="Converters\BitmapTypeConverter.cs" />
+    <Compile Include="Converters\IconTypeConverter.cs" />
+    <Compile Include="Converters\AvaloniaPropertyTypeConverter.cs" />
+    <Compile Include="Converters\PointsListTypeConverter.cs" />
+    <Compile Include="MarkupExtensions\ReflectionBindingExtension.cs" />
+    <Compile Include="MarkupExtensions\RelativeSourceExtension.cs" />
+    <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="RuntimeXamlLoaderConfiguration.cs" />
+    <Compile Include="RuntimeXamlLoaderDocument.cs" />
+    <Compile Include="Styling\MergeResourceInclude.cs" />
+    <Compile Include="Styling\ResourceInclude.cs" />
+    <Compile Include="Styling\StyleInclude.cs" />
+    <Compile Include="Templates\ControlTemplate.cs" />
+    <Compile Include="Templates\DataTemplate.cs" />
+    <Compile Include="Templates\FocusAdornerTemplate.cs" />
+    <Compile Include="Templates\ItemsPanelTemplate.cs" />
+    <Compile Include="Templates\Template.cs" />
+    <Compile Include="Templates\TemplateContent.cs" />
+    <Compile Include="Templates\TreeDataTemplate.cs" />
+    <Compile Include="XamlIl\Runtime\IAvaloniaXamlIlControlTemplateProvider.cs" />
+    <Compile Include="XamlIl\Runtime\IAvaloniaXamlIlParentStackProvider.cs" />
+    <Compile Include="XamlIl\Runtime\IAvaloniaXamlIlXmlNamespaceInfoProviderV1.cs" />
+    <Compile Include="XamlIl\Runtime\XamlIlRuntimeHelpers.cs" />
+    <Compile Include="XamlLoadException.cs" />
+    <Compile Include="XamlTypes.cs" />
+  </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\Avalonia.Base\Avalonia.Base.csproj" />
     <ProjectReference Include="..\..\Avalonia.Controls\Avalonia.Controls.csproj" />
@@ -72,6 +66,7 @@
   <ItemGroup Label="InternalsVisibleTo">
     <InternalsVisibleTo Include="Avalonia.Designer.HostApp, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.DesignerSupport, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.Base.UnitTests, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Markup.Xaml.Loader, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Markup.Xaml.UnitTests, PublicKey=$(AvaloniaPublicKey)" />
   </ItemGroup>
diff --git a/src/Markup/Avalonia.Markup.Xaml/Data/DynamicResourceExpression.cs b/src/Markup/Avalonia.Markup.Xaml/Data/DynamicResourceExpression.cs
new file mode 100644
index 000000000..438c14039
--- /dev/null
+++ b/src/Markup/Avalonia.Markup.Xaml/Data/DynamicResourceExpression.cs
@@ -0,0 +1,155 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
+using Avalonia.Controls;
+using Avalonia.Data;
+using Avalonia.Data.Core;
+using Avalonia.Logging;
+using Avalonia.Markup.Xaml.Converters;
+using Avalonia.Media;
+using Avalonia.Styling;
+
+namespace Avalonia.Markup.Xaml.MarkupExtensions
+{
+    internal class DynamicResourceExpression : UntypedBindingExpressionBase
+    {
+        private readonly object _resourceKey;
+        private readonly object? _anchor;
+        private IResourceHost? _host;
+        private IResourceProvider? _provider;
+        private bool _overrideThemeVariant;
+        private bool _targetTypeIsBrush;
+        private ThemeVariant? _themeVariant;
+
+        public DynamicResourceExpression(
+            object resourceKey,
+            object? anchor,
+            ThemeVariant? themeVariant,
+            BindingPriority priority)
+            : base(priority)
+        {
+            _resourceKey = resourceKey;
+            _anchor = anchor;
+            _themeVariant = themeVariant;
+        }
+
+        public override string Description => $"DynamicResource {_resourceKey}";
+
+        protected override void StartCore()
+        {
+            if (!TryGetResourceHost(out _host))
+            {
+                // The target is not an IResourceHost, so we need to find one from the anchor.
+                if (_anchor is IResourceProvider provider)
+                {
+                    _provider = provider;
+                    _host = provider.Owner;
+                    _overrideThemeVariant = _themeVariant is not null;
+                }
+            }
+
+            // If we wouldn't find a host or provider then log an error: we can't do anything.
+            if (_host is null && _provider is null)
+            {
+                Log("Unable to find IResourceHost or IResourceProvider from which to lookup " +
+                    $"DynamicResource {_resourceKey}.", LogEventLevel.Error);
+                return;
+            }
+
+            // Hook up events.
+            if (_provider is not null)
+                _provider.OwnerChanged += OnResourceProviderOwnerChanged;
+            Subscribe(_host);
+
+            // And publish the initial value.
+            _targetTypeIsBrush = TargetType == typeof(IBrush);
+            PublishValue();
+        }
+
+        protected override void StopCore()
+        {
+            if (_provider is not null)
+                _provider.OwnerChanged -= OnResourceProviderOwnerChanged;
+            Unsubscribe(_host);
+            _host = null;
+            _provider = null;
+        }
+
+        private void OnResourceProviderOwnerChanged(object? sender, EventArgs e)
+        {
+            Unsubscribe(_host);
+            _host = _provider?.Owner;
+            Subscribe(_host);
+            PublishValue();
+        }
+
+        private void ResourcesChanged(object? sender, ResourcesChangedEventArgs e) => PublishValue();
+
+        private void ActualThemeVariantChanged(object? sender, EventArgs e)
+        {
+            if (!IsRunning)
+                return;
+
+            _themeVariant = ((IThemeVariantHost)sender!).ActualThemeVariant;
+            PublishValue();
+        }
+
+        private void PublishValue()
+        {
+            if (_host is not null)
+            {
+                var theme = _themeVariant;
+                var value = _host.FindResource(theme, _resourceKey) ?? AvaloniaProperty.UnsetValue;
+                var convertedValue = _targetTypeIsBrush ?
+                    ColorToBrushConverter.Convert(value, typeof(IBrush)) :
+                    value;
+                PublishValue(convertedValue);
+            }
+            else
+            {
+                PublishValue(AvaloniaProperty.UnsetValue);
+            }
+        }
+
+        private bool TryGetResourceHost([NotNullWhen(true)] out IResourceHost? host)
+        {
+            if (TryGetTarget(out var target) && target is IResourceHost targetHost)
+            {
+                host = targetHost;
+                return true;
+            }
+
+            if (_anchor is IResourceHost anchorHost)
+            {
+                host = anchorHost;
+                return host is not null;
+            }
+
+            host = null;
+            return false;
+        }
+
+        private void Subscribe(IResourceHost? host)
+        {
+            if (host is not null)
+            {
+                host.ResourcesChanged += ResourcesChanged;
+                
+                if (!_overrideThemeVariant && _host is IThemeVariantHost themeVariantHost)
+                {
+                    _themeVariant = themeVariantHost.ActualThemeVariant;
+                    themeVariantHost.ActualThemeVariantChanged += ActualThemeVariantChanged;
+                }
+            }
+        }
+
+        private void Unsubscribe(IResourceHost? host)
+        {
+            if (host is not null)
+            {
+                host.ResourcesChanged -= ResourcesChanged;
+                if (!_overrideThemeVariant && _host is IThemeVariantHost themeVariantHost)
+                    themeVariantHost.ActualThemeVariantChanged -= ActualThemeVariantChanged;
+            }
+        }
+    }
+}
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindingExtension.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindingExtension.cs
index 0b7b488b4..cc6e44f4d 100644
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindingExtension.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindingExtension.cs
@@ -1,8 +1,11 @@
 using System;
+using System.Collections.Generic;
 using Avalonia.Data;
-using Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings;
 using Avalonia.Data.Core;
+using Avalonia.Data.Core.ExpressionNodes;
+using Avalonia.Diagnostics;
 using Avalonia.Markup.Parsers;
+using Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings;
 
 namespace Avalonia.Markup.Xaml.MarkupExtensions
 {
@@ -32,51 +35,106 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
                 Priority = Priority,
                 StringFormat = StringFormat,
                 Source = Source,
-                DefaultAnchor = new WeakReference(provider.GetDefaultAnchor())
+                DefaultAnchor = new WeakReference(provider.GetDefaultAnchor()),
+                UpdateSourceTrigger = UpdateSourceTrigger,
             };
         }
 
-        private protected override ExpressionObserver CreateExpressionObserver(AvaloniaObject target, AvaloniaProperty? targetProperty, object? anchor, bool enableDataValidation)
-        {
-            if (Source != null)
-            {
-                return CreateSourceObserver(
-                    Source,
-                    Path.BuildExpression(enableDataValidation));
-            }
-
-            if (Path.RawSource != null)
-            {
-                return CreateSourceObserver(
-                    Path.RawSource,
-                    Path.BuildExpression(enableDataValidation));
-            }
-
-            if (Path.SourceMode == SourceMode.Data)
-            {
-                return CreateDataContextObserver(
-                    target,
-                    Path.BuildExpression(enableDataValidation),
-                    targetProperty == StyledElement.DataContextProperty,
-                    anchor);
-            }
-            else
-            {
-                var styledElement = target as StyledElement
-                    ?? anchor as StyledElement
-                    ?? throw new ArgumentException($"Cannot find a valid {nameof(StyledElement)} to use as the binding source.");
-
-                return CreateSourceObserver(
-                    styledElement,
-                    Path.BuildExpression(enableDataValidation));
-            }
-        }
-
         [ConstructorArgument("path")]
         public CompiledBindingPath Path { get; set; }
 
-        public object? Source { get; set; }
+        public object? Source { get; set; } = AvaloniaProperty.UnsetValue;
 
         public Type? DataType { get; set; }
+
+        [Obsolete(ObsoletionMessages.MayBeRemovedInAvalonia12)]
+        public override InstancedBinding? Initiate(
+            AvaloniaObject target,
+            AvaloniaProperty? targetProperty,
+            object? anchor = null,
+            bool enableDataValidation = false)
+        {
+            var expression = InstanceCore(target, targetProperty, anchor, enableDataValidation);
+            return new InstancedBinding(target, expression, Mode, Priority);
+        }
+
+        private protected override BindingExpressionBase Instance(
+            AvaloniaProperty targetProperty,
+            AvaloniaObject target,
+            object? anchor)
+        {
+            var enableDataValidation = targetProperty.GetMetadata(target.GetType()).EnableDataValidation ?? false;
+            return InstanceCore(target, targetProperty, anchor, enableDataValidation);
+        }
+
+        /// <summary>
+        /// Hack for TreeDataTemplate to create a binding expression for an item.
+        /// </summary>
+        /// <param name="source">The item.</param>
+        /// <remarks>
+        /// Ideally we'd do this in a more generic way but didn't have time to refactor
+        /// ITreeDataTemplate in time for 11.0. We should revisit this in 12.0.
+        /// </remarks>
+        // TODO12: Refactor
+        internal BindingExpression CreateObservableForTreeDataTemplate(object source)
+        {
+            if (Source != AvaloniaProperty.UnsetValue)
+                throw new NotSupportedException("Source bindings are not supported in this context.");
+
+            var nodes = new List<ExpressionNode>();
+
+            Path.BuildExpression(nodes, out var isRooted);
+
+            if (isRooted)
+                throw new NotSupportedException("Rooted binding paths are not supported in this context.");
+
+            return new BindingExpression(
+                source,
+                nodes,
+                FallbackValue,
+                converter: Converter,
+                converterParameter: ConverterParameter,
+                targetNullValue: TargetNullValue);
+        }
+
+        private BindingExpression InstanceCore(
+            AvaloniaObject target,
+            AvaloniaProperty? targetProperty,
+            object? anchor,
+            bool enableDataValidation)
+        {
+            var nodes = new List<ExpressionNode>();
+
+            // Build the expression nodes from the binding path.
+            Path.BuildExpression(nodes, out var isRooted);
+
+            // If the binding isn't rooted (i.e. doesn't have a Source or start with $parent, $self,
+            // #elementName etc.) then we need to add a data context source node.
+            if (Source == AvaloniaProperty.UnsetValue && !isRooted)
+                nodes.Insert(0, ExpressionNodeFactory.CreateDataContext(targetProperty));
+
+            // If the first node is an ISourceNode then allow it to select the source; otherwise
+            // use the binding source if specified, falling back to the target.
+            var source = nodes.Count > 0 && nodes[0] is SourceNode sn
+                ? sn.SelectSource(Source, target, anchor ?? DefaultAnchor?.Target)
+                : Source != AvaloniaProperty.UnsetValue ? Source : target;
+
+            var (mode, trigger) = ResolveDefaultsFromMetadata(target, targetProperty);
+
+            return new BindingExpression(
+                source,
+                nodes,
+                FallbackValue,
+                converter: Converter,
+                converterCulture: ConverterCulture,
+                converterParameter: ConverterParameter,
+                enableDataValidation: enableDataValidation,
+                mode: mode,
+                priority: Priority,
+                stringFormat: StringFormat,
+                targetNullValue: TargetNullValue,
+                targetTypeConverter: TargetTypeConverter.GetDefaultConverter(),
+                updateSourceTrigger: trigger);
+        }
     }
 }
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/ArrayElementPlugin.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/ArrayElementPlugin.cs
deleted file mode 100644
index ffd62dc85..000000000
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/ArrayElementPlugin.cs
+++ /dev/null
@@ -1,72 +0,0 @@
-using System;
-using System.Diagnostics.CodeAnalysis;
-using Avalonia.Data;
-using Avalonia.Data.Core.Plugins;
-
-namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
-{
-    internal class ArrayElementPlugin : IPropertyAccessorPlugin
-    {
-        private readonly int[] _indices;
-        private readonly Type _elementType;
-
-        public ArrayElementPlugin(int[] indices, Type elementType)
-        {
-            _indices = indices;
-            _elementType = elementType;
-        }
-
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
-        public bool Match(object obj, string propertyName)
-        {
-            throw new InvalidOperationException("The ArrayElementPlugin does not support dynamic matching");
-        }
-
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
-        public IPropertyAccessor? Start(WeakReference<object?> reference, string propertyName)
-        {
-            if (reference.TryGetTarget(out var target) && target is Array arr)
-            {
-                return new Accessor(new WeakReference<Array>(arr), _indices, _elementType);
-            }
-            return null;
-        }
-
-        class Accessor : PropertyAccessorBase
-        {
-            private readonly int[] _indices;
-            private readonly WeakReference<Array> _reference;
-
-            public Accessor(WeakReference<Array> reference, int[] indices, Type elementType)
-            {
-                _reference = reference;
-                _indices = indices;
-                PropertyType = elementType;
-            }
-
-            public override Type PropertyType { get; }
-
-            public override object? Value => _reference.TryGetTarget(out var arr) ? arr.GetValue(_indices) : null;
-
-            public override bool SetValue(object? value, BindingPriority priority)
-            {
-                if (_reference.TryGetTarget(out var arr))
-                {
-                    arr.SetValue(value, _indices);
-                    return true;
-                }
-                return false;
-            }
-
-            protected override void SubscribeCore()
-            {
-                PublishValue(Value);
-            }
-
-            protected override void UnsubscribeCore()
-            {
-            }
-        }
-    }
-
-}
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/CommandAccessorPlugin.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/CommandAccessorPlugin.cs
deleted file mode 100644
index b9bc2a1e3..000000000
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/CommandAccessorPlugin.cs
+++ /dev/null
@@ -1,155 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.ComponentModel;
-using System.Diagnostics.CodeAnalysis;
-using System.Windows.Input;
-using Avalonia.Data;
-using Avalonia.Data.Core.Plugins;
-using Avalonia.Utilities;
-
-namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
-{
-    internal class CommandAccessorPlugin : IPropertyAccessorPlugin
-    {
-        private readonly Action<object, object?> _execute;
-        private readonly Func<object, object?, bool>? _canExecute;
-        private readonly ISet<string> _dependsOnProperties;
-
-        public CommandAccessorPlugin(Action<object, object?> execute, Func<object, object?, bool>? canExecute, ISet<string> dependsOnProperties)
-        {
-            _execute = execute;
-            _canExecute = canExecute;
-            _dependsOnProperties = dependsOnProperties;
-        }
-
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
-        public bool Match(object obj, string propertyName)
-        {
-            throw new InvalidOperationException("The CommandAccessorPlugin does not support dynamic matching");
-        }
-
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
-        public IPropertyAccessor Start(WeakReference<object?> reference, string propertyName)
-        {
-            return new CommandAccessor(reference, _execute, _canExecute, _dependsOnProperties);
-        }
-
-        private sealed class CommandAccessor : PropertyAccessorBase
-        {
-            private readonly WeakReference<object?> _reference;
-            private readonly Command _command;
-            private readonly ISet<string> _dependsOnProperties;
-
-            public CommandAccessor(WeakReference<object?> reference, Action<object, object?> execute, Func<object, object?, bool>? canExecute, ISet<string> dependsOnProperties)
-            {
-                _reference = reference ?? throw new ArgumentNullException(nameof(reference));
-                _dependsOnProperties = dependsOnProperties;
-                _command = new Command(reference, execute, canExecute);
-
-            }
-
-            public override object? Value => _reference.TryGetTarget(out _) ? _command : null;
-
-            private void RaiseCanExecuteChanged()
-            {
-                _command.RaiseCanExecuteChanged();
-            }
-
-            private sealed class Command : ICommand
-            {
-                private readonly WeakReference<object?> _target;
-                private readonly Action<object, object?> _execute;
-                private readonly Func<object, object?, bool>? _canExecute;
-
-                public event EventHandler? CanExecuteChanged;
-
-                public Command(WeakReference<object?> target, Action<object, object?> execute, Func<object, object?, bool>? canExecute)
-                {
-                    _target = target;
-                    _execute = execute;
-                    _canExecute = canExecute;
-                }
-
-                public void RaiseCanExecuteChanged()
-                {
-                    Threading.Dispatcher.UIThread.Post(() => CanExecuteChanged?.Invoke(this, EventArgs.Empty)
-                       , Threading.DispatcherPriority.Input);
-                }
-
-                public bool CanExecute(object? parameter)
-                {
-                    if (_target.TryGetTarget(out var target))
-                    {
-                        if (_canExecute == null)
-                        {
-                            return true;
-                        }
-                        return _canExecute(target, parameter);
-                    }
-                    return false;
-                }
-
-                public void Execute(object? parameter)
-                {
-                    if (_target.TryGetTarget(out var target))
-                    {
-                        _execute(target, parameter);
-                    }
-                }
-            }
-
-            public override Type PropertyType => typeof(ICommand);
-
-            public override bool SetValue(object? value, BindingPriority priority)
-            {
-                return false;
-            }
-
-            private void OnNotifyPropertyChanged(object? sender, PropertyChangedEventArgs e)
-            {
-                if (string.IsNullOrEmpty(e.PropertyName) || _dependsOnProperties.Contains(e.PropertyName))
-                {
-                    RaiseCanExecuteChanged();
-                }
-            }
-
-            protected override void SubscribeCore()
-            {
-                SendCurrentValue();
-                SubscribeToChanges();
-            }
-
-            protected override void UnsubscribeCore()
-            {
-                if (_dependsOnProperties is { Count: > 0 } && _reference.TryGetTarget(out var o) && o is INotifyPropertyChanged inpc)
-                {
-                    WeakEventHandlerManager.Unsubscribe<PropertyChangedEventArgs, CommandAccessor>(
-                        inpc,
-                        nameof(INotifyPropertyChanged.PropertyChanged),
-                        OnNotifyPropertyChanged);
-                }
-            }
-
-            private void SendCurrentValue()
-            {
-                try
-                {
-                    var value = Value;
-                    PublishValue(value);
-                }
-                catch { }
-            }
-
-            private void SubscribeToChanges()
-            {
-                if (_dependsOnProperties is { Count:>0 } && _reference.TryGetTarget(out var o) && o is INotifyPropertyChanged inpc)
-                {
-                    WeakEventHandlerManager.Subscribe<INotifyPropertyChanged, PropertyChangedEventArgs, CommandAccessor>(
-                        inpc,
-                        nameof(INotifyPropertyChanged.PropertyChanged),
-                        OnNotifyPropertyChanged);
-                }
-            }
-        }
-    }
-}
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/CompiledBindingPath.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/CompiledBindingPath.cs
index 73da7a7fe..7249c389d 100644
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/CompiledBindingPath.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/CompiledBindingPath.cs
@@ -1,12 +1,11 @@
 using System;
 using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
 using System.Reflection;
 using Avalonia.Controls;
 using Avalonia.Data.Core;
+using Avalonia.Data.Core.ExpressionNodes;
 using Avalonia.Data.Core.Plugins;
 using Avalonia.Markup.Parsers;
-using Avalonia.Markup.Parsers.Nodes;
 
 namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
 {
@@ -23,57 +22,74 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
             RawSource = rawSource;
         }
 
-        [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = TrimmingMessages.CompiledBindingSafeSupressWarningMessage)]
-        internal ExpressionNode BuildExpression(bool enableValidation)
+        internal void BuildExpression(List<ExpressionNode> result, out bool isRooted)
         {
-            ExpressionNode? pathRoot = null;
-            ExpressionNode? path = null;
+            var negated = 0;
+
+            isRooted = false;
+
             foreach (var element in _elements)
             {
                 ExpressionNode? node;
                 switch (element)
                 {
                     case NotExpressionPathElement:
-                        node = new LogicalNotNode();
+                        ++negated;
+                        node = null;
                         break;
                     case PropertyElement prop:
-                        node = new PropertyAccessorNode(prop.Property.Name, enableValidation, new PropertyInfoAccessorPlugin(prop.Property, prop.AccessorFactory));
+                        node = new PropertyAccessorNode(prop.Property.Name, new PropertyInfoAccessorPlugin(prop.Property, prop.AccessorFactory));
                         break;
                     case MethodAsCommandElement methodAsCommand:
-                        node = new PropertyAccessorNode(methodAsCommand.MethodName, enableValidation, new CommandAccessorPlugin(methodAsCommand.ExecuteMethod, methodAsCommand.CanExecuteMethod, methodAsCommand.DependsOnProperties));
+                        node = new MethodCommandNode(
+                            methodAsCommand.MethodName,
+                            methodAsCommand.ExecuteMethod,
+                            methodAsCommand.CanExecuteMethod,
+                            methodAsCommand.DependsOnProperties);
                         break;
                     case MethodAsDelegateElement methodAsDelegate:
-                        node = new PropertyAccessorNode(methodAsDelegate.Method.Name, enableValidation, new MethodAccessorPlugin(methodAsDelegate.Method, methodAsDelegate.DelegateType));
+                        node = new PropertyAccessorNode(methodAsDelegate.Method.Name, new MethodAccessorPlugin(methodAsDelegate.Method, methodAsDelegate.DelegateType));
                         break;
                     case ArrayElementPathElement arr:
-                        node = new PropertyAccessorNode(CommonPropertyNames.IndexerName, enableValidation, new ArrayElementPlugin(arr.Indices, arr.ElementType));
+                        node = new ArrayIndexerNode(arr.Indices);
                         break;
                     case VisualAncestorPathElement visualAncestor:
-                        node = new FindVisualAncestorNode(visualAncestor.AncestorType, visualAncestor.Level);
+                        node = new VisualAncestorElementNode(visualAncestor.AncestorType, visualAncestor.Level);
+                        isRooted = true;
                         break;
                     case AncestorPathElement ancestor:
-                        node = new FindAncestorNode(ancestor.AncestorType, ancestor.Level);
+                        node = new LogicalAncestorElementNode(ancestor.AncestorType, ancestor.Level);
+                        isRooted = true;
                         break;
                     case SelfPathElement:
-                        node = new SelfNode();
+                        node = null;
+                        isRooted = true;
                         break;
                     case ElementNameElement name:
-                        node = new ElementNameNode(name.NameScope, name.Name);
+                        node = new NamedElementNode(name.NameScope, name.Name);
+                        isRooted = true;
                         break;
                     case IStronglyTypedStreamElement stream:
                         node = new StreamNode(stream.CreatePlugin());
                         break;
                     case ITypeCastElement typeCast:
-                        node = new StrongTypeCastNode(typeCast.Type, typeCast.Cast);
+                        node = new FuncTransformNode(typeCast.Cast);
+                        break;
+                    case TemplatedParentPathElement:
+                        node = new TemplatedParentNode();
+                        isRooted = true;
                         break;
                     default:
                         throw new InvalidOperationException($"Unknown binding path element type {element.GetType().FullName}");
                 }
 
-                path = pathRoot is null ? (pathRoot = node) : path!.Next = node;
+                if (node is not null)
+                    result.Add(node);
             }
 
-            return pathRoot ?? new EmptyExpressionNode();
+
+            for (var i = 0; i < negated; ++i)
+                result.Add(new LogicalNotNode());
         }
 
         internal IEnumerable<ICompiledBindingPathElement> Elements => _elements;
@@ -90,9 +106,18 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
 
     public class CompiledBindingPathBuilder
     {
+        private readonly int _apiVersion;
         private object? _rawSource;
         private readonly List<ICompiledBindingPathElement> _elements = new();
 
+        public CompiledBindingPathBuilder()
+        {
+        }
+
+        // TODO12: Remove this constructor. apiVersion is only needed for compatibility with
+        // versions of Avalonia which used $self.Property() for building TemplatedParent bindings.
+        public CompiledBindingPathBuilder(int apiVersion) => _apiVersion = apiVersion;
+
         public CompiledBindingPathBuilder Not()
         {
             _elements.Add(new NotExpressionPathElement());
@@ -101,7 +126,21 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
 
         public CompiledBindingPathBuilder Property(IPropertyInfo info, Func<WeakReference<object?>, IPropertyInfo, IPropertyAccessor> accessorFactory)
         {
-            _elements.Add(new PropertyElement(info, accessorFactory, _elements.Count == 0));
+            // Older versions of Avalonia used $self.Property() for building TemplatedParent bindings.
+            // Try to detect this and upgrade to using a TemplatedParentPathElement so that logging works
+            // correctly.
+            if (_apiVersion == 0 && 
+                info.Name == "TemplatedParent" && 
+                _elements.Count >= 1 &&
+                _elements[_elements.Count - 1] is SelfPathElement)
+            {
+                _elements.Add(new TemplatedParentPathElement());
+            }
+            else
+            {
+                _elements.Add(new PropertyElement(info, accessorFactory, _elements.Count == 0));
+            }
+
             return this;
         }
 
@@ -140,6 +179,7 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
             _elements.Add(new AncestorPathElement(ancestorType, level));
             return this;
         }
+
         public CompiledBindingPathBuilder VisualAncestor(Type ancestorType, int level)
         {
             _elements.Add(new VisualAncestorPathElement(ancestorType, level));
@@ -164,6 +204,12 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
             return this;
         }
 
+        public CompiledBindingPathBuilder TemplatedParent()
+        {
+            _elements.Add(new TemplatedParentPathElement());
+            return this;
+        }
+
         public CompiledBindingPathBuilder SetRawSource(object? rawSource)
         {
             _rawSource = rawSource;
@@ -309,6 +355,12 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
             => $"#{Name}";
     }
 
+    internal class TemplatedParentPathElement : ICompiledBindingPathElement, IControlSourceBindingPathElement
+    {
+        public override string ToString()
+            => $"$templatedParent";
+    }
+
     internal class ArrayElementPathElement : ICompiledBindingPathElement
     {
         public ArrayElementPathElement(int[] indices, Type elementType)
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/FindVisualAncestorNode.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/FindVisualAncestorNode.cs
deleted file mode 100644
index 7c20f8607..000000000
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/FindVisualAncestorNode.cs
+++ /dev/null
@@ -1,53 +0,0 @@
-using System;
-using Avalonia.Data.Core;
-using Avalonia.VisualTree;
-using Avalonia.Reactive;
-
-namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
-{
-    internal class FindVisualAncestorNode : ExpressionNode
-    {
-        private readonly int _level;
-        private readonly Type? _ancestorType;
-        private IDisposable? _subscription;
-
-        public FindVisualAncestorNode(Type? ancestorType, int level)
-        {
-            _level = level;
-            _ancestorType = ancestorType;
-        }
-
-        public override string Description
-        {
-            get
-            {
-                if (_ancestorType == null)
-                {
-                    return FormattableString.Invariant($"$visualparent[{_level}]");
-                }
-                else
-                {
-                    return FormattableString.Invariant($"$visualparent[{_ancestorType.Name}, {_level}]");
-                }
-            }
-        }
-
-        protected override void StartListeningCore(WeakReference<object?> reference)
-        {
-            if (reference.TryGetTarget(out object? target) && target is Visual visual)
-            {
-                _subscription = VisualLocator.Track(visual, _level, _ancestorType).Subscribe(ValueChanged);
-            }
-            else
-            {
-                _subscription = null;
-            }
-        }
-
-        protected override void StopListeningCore()
-        {
-            _subscription?.Dispose();
-            _subscription = null;
-        }
-    }
-}
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/MethodAccessorPlugin.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/MethodAccessorPlugin.cs
deleted file mode 100644
index e4d36a33a..000000000
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/MethodAccessorPlugin.cs
+++ /dev/null
@@ -1,73 +0,0 @@
-using System;
-using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
-using System.Reflection;
-using Avalonia.Data;
-using Avalonia.Data.Core.Plugins;
-
-namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
-{
-    internal class MethodAccessorPlugin : IPropertyAccessorPlugin
-    {
-        private readonly MethodInfo _method;
-        private readonly Type _delegateType;
-
-        public MethodAccessorPlugin(MethodInfo method, Type delegateType)
-        {
-            _method = method;
-            _delegateType = delegateType;
-        }
-
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
-        public bool Match(object obj, string propertyName)
-        {
-            throw new InvalidOperationException("The MethodAccessorPlugin does not support dynamic matching");
-        }
-
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
-        public IPropertyAccessor Start(WeakReference<object?> reference, string propertyName)
-        {
-            Debug.Assert(_method.Name == propertyName);
-            return new Accessor(reference, _method, _delegateType);
-        }
-
-        private sealed class Accessor : PropertyAccessorBase
-        {
-            public Accessor(WeakReference<object?> reference, MethodInfo method, Type delegateType)
-            {
-                _ = reference ?? throw new ArgumentNullException(nameof(reference));
-                _ = method ?? throw new ArgumentNullException(nameof(method));
-
-                PropertyType = delegateType;
-
-                if (method.IsStatic)
-                {
-                    Value = method.CreateDelegate(PropertyType);
-                }
-                else if (reference.TryGetTarget(out var target))
-                {
-                    Value = method.CreateDelegate(PropertyType, target);
-                }
-            }
-
-            public override Type? PropertyType { get; }
-
-            public override object? Value { get; }
-
-            public override bool SetValue(object? value, BindingPriority priority) => false;
-
-            protected override void SubscribeCore()
-            {
-                try
-                {
-                    PublishValue(Value);
-                }
-                catch { }
-            }
-
-            protected override void UnsubscribeCore()
-            {
-            }
-        }
-    }
-}
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/ObservableStreamPlugin.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/ObservableStreamPlugin.cs
deleted file mode 100644
index 93ff1ceac..000000000
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/ObservableStreamPlugin.cs
+++ /dev/null
@@ -1,31 +0,0 @@
-using System;
-using System.Diagnostics.CodeAnalysis;
-using Avalonia.Data.Core.Plugins;
-using Avalonia.Reactive;
-
-namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
-{
-    internal class ObservableStreamPlugin<T> : IStreamPlugin
-    {
-        [RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
-        public bool Match(WeakReference<object?> reference)
-        {
-            return reference.TryGetTarget(out var target) && target is IObservable<T>;
-        }
-
-        [RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
-        public IObservable<object?> Start(WeakReference<object?> reference)
-        {
-            if (!(reference.TryGetTarget(out var target) && target is IObservable<T> obs))
-            {
-                return Observable.Empty<object?>();
-            }
-            else if (target is IObservable<object?> obj)
-            {
-                return obj;
-            }
-
-            return obs.Select(x => (object?)x);
-        }
-    }
-}
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/PropertyInfoAccessorFactory.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/PropertyInfoAccessorFactory.cs
index c8e65ff67..6c00df5b6 100644
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/PropertyInfoAccessorFactory.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/PropertyInfoAccessorFactory.cs
@@ -132,7 +132,10 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
                 var value = Value;
                 PublishValue(value);
             }
-            catch { }
+            catch (Exception e)
+            {
+                PublishValue(new BindingNotification(e, BindingErrorType.Error));
+            }
         }
 
         private void SubscribeToChanges()
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/PropertyInfoAccessorPlugin.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/PropertyInfoAccessorPlugin.cs
deleted file mode 100644
index 631f71faa..000000000
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/PropertyInfoAccessorPlugin.cs
+++ /dev/null
@@ -1,33 +0,0 @@
-using System;
-using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
-using Avalonia.Data.Core;
-using Avalonia.Data.Core.Plugins;
-
-namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
-{
-    internal class PropertyInfoAccessorPlugin : IPropertyAccessorPlugin
-    {
-        private readonly IPropertyInfo _propertyInfo;
-        private readonly Func<WeakReference<object?>, IPropertyInfo, IPropertyAccessor> _accessorFactory;
-
-        public PropertyInfoAccessorPlugin(IPropertyInfo propertyInfo, Func<WeakReference<object?>, IPropertyInfo, IPropertyAccessor> accessorFactory)
-        {
-            _propertyInfo = propertyInfo;
-            _accessorFactory = accessorFactory;
-        }
-
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
-        public bool Match(object obj, string propertyName)
-        {
-            throw new InvalidOperationException("The PropertyInfoAccessorPlugin does not support dynamic matching");
-        }
-
-        [RequiresUnreferencedCode(TrimmingMessages.PropertyAccessorsRequiresUnreferencedCodeMessage)]
-        public IPropertyAccessor Start(WeakReference<object?> reference, string propertyName)
-        {
-            Debug.Assert(_propertyInfo.Name == propertyName);
-            return _accessorFactory(reference, _propertyInfo);
-        }
-    }
-}
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/StrongTypeCastNode.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/StrongTypeCastNode.cs
deleted file mode 100644
index 360d34c88..000000000
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/StrongTypeCastNode.cs
+++ /dev/null
@@ -1,18 +0,0 @@
-using System;
-using Avalonia.Data.Core;
-
-namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
-{
-    internal class StrongTypeCastNode : TypeCastNode
-    {
-        private readonly Func<object?, object?> _cast;
-
-        public StrongTypeCastNode(Type type, Func<object?, object?> cast) : base(type)
-        {
-            _cast = cast;
-        }
-
-        protected override object? Cast(object? value)
-            => _cast(value);
-    }
-}
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/TaskStreamPlugin.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/TaskStreamPlugin.cs
index 6f3e444ca..34e4a730c 100644
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/TaskStreamPlugin.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/TaskStreamPlugin.cs
@@ -1,5 +1,4 @@
 using System;
-using System.Diagnostics.CodeAnalysis;
 using System.Threading.Tasks;
 using Avalonia.Data;
 using Avalonia.Data.Core.Plugins;
@@ -9,13 +8,11 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
 {
     internal class TaskStreamPlugin<T> : IStreamPlugin
     {
-        [RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
         public bool Match(WeakReference<object?> reference)
         {
             return reference.TryGetTarget(out var target) && target is Task<T>;
         }
 
-        [RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
         public IObservable<object?> Start(WeakReference<object?> reference)
         {
             if(!(reference.TryGetTarget(out var target) && target is Task<T> task))
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/DynamicResourceExtension.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/DynamicResourceExtension.cs
index 7f52c872e..0167b3b89 100644
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/DynamicResourceExtension.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/DynamicResourceExtension.cs
@@ -1,17 +1,16 @@
 using System;
 using Avalonia.Controls;
 using Avalonia.Data;
-using Avalonia.Markup.Xaml.Converters;
-using Avalonia.Media;
+using Avalonia.Data.Core;
 using Avalonia.Styling;
 
 namespace Avalonia.Markup.Xaml.MarkupExtensions
 {
-    public class DynamicResourceExtension : IBinding
+    public class DynamicResourceExtension : IBinding2
     {
         private object? _anchor;
         private BindingPriority _priority;
-        private ThemeVariant? _currentThemeVariant;
+        private ThemeVariant? _themeVariant;
 
         public DynamicResourceExtension()
         {
@@ -38,7 +37,7 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
                     (object?)serviceProvider.GetFirstParent<IResourceHost>();
             }
 
-            _currentThemeVariant = StaticResourceExtension.GetDictionaryVariant(serviceProvider);
+            _themeVariant = StaticResourceExtension.GetDictionaryVariant(serviceProvider);
 
             return this;
         }
@@ -50,34 +49,16 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
             bool enableDataValidation)
         {
             if (ResourceKey is null)
-            {
                 return null;
-            }
-
-            var control = target as IResourceHost ?? _anchor as IResourceHost;
-
-            if (control != null)
-            {
-                var source = control.GetResourceObservable(ResourceKey, GetConverter(targetProperty));
-                return InstancedBinding.OneWay(source, _priority);
-            }
-            else if (_anchor is IResourceProvider resourceProvider)
-            {
-                var source = resourceProvider.GetResourceObservable(ResourceKey, _currentThemeVariant, GetConverter(targetProperty));
-                return InstancedBinding.OneWay(source, _priority);
-            }
-
-            return null;
+            var expression = new DynamicResourceExpression(ResourceKey, _anchor, _themeVariant, _priority);
+            return new InstancedBinding(target, expression, BindingMode.OneWay, _priority);
         }
 
-        private static Func<object?, object?>? GetConverter(AvaloniaProperty? targetProperty)
+        BindingExpressionBase IBinding2.Instance(AvaloniaObject target, AvaloniaProperty targetProperty, object? anchor)
         {
-            if (targetProperty?.PropertyType == typeof(IBrush))
-            {
-                return x => ColorToBrushConverter.Convert(x, typeof(IBrush));
-            }
-
-            return null;
+            if (ResourceKey is null)
+                throw new InvalidOperationException("DynamicResource must have a ResourceKey.");
+            return new DynamicResourceExpression(ResourceKey, _anchor, _themeVariant, _priority);
         }
     }
 }
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/ReflectionBindingExtension.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/ReflectionBindingExtension.cs
index c32804886..d71502c33 100644
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/ReflectionBindingExtension.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/ReflectionBindingExtension.cs
@@ -60,7 +60,7 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
 
         public BindingPriority Priority { get; set; } = BindingPriority.LocalValue;
 
-        public object? Source { get; set; }
+        public object? Source { get; set; } = AvaloniaProperty.UnsetValue;
 
         public string? StringFormat { get; set; }
 
diff --git a/src/Markup/Avalonia.Markup.Xaml/Templates/TreeDataTemplate.cs b/src/Markup/Avalonia.Markup.Xaml/Templates/TreeDataTemplate.cs
index 98c3b61c9..9f34bf202 100644
--- a/src/Markup/Avalonia.Markup.Xaml/Templates/TreeDataTemplate.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/Templates/TreeDataTemplate.cs
@@ -34,19 +34,19 @@ namespace Avalonia.Markup.Xaml.Templates
             }
         }
 
-        [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = "If ItemsSource is a CompiledBinding, then path members will be preserver")]
+        [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = "If ItemsSource is a CompiledBinding, then path members will be preserved")]
         public InstancedBinding? ItemsSelector(object item)
         {
             if (ItemsSource != null)
             {
-                var obs = ItemsSource switch
+                var expression = ItemsSource switch
                 {
-                    Binding reflection => ExpressionObserverBuilder.Build(item, reflection.Path),
-                    CompiledBindingExtension compiled => new ExpressionObserver(item, compiled.Path.BuildExpression(false)),
+                    Binding reflection => reflection.CreateObservableForTreeDataTemplate(item),
+                    CompiledBindingExtension compiled => compiled.CreateObservableForTreeDataTemplate(item),
                     _ => throw new InvalidOperationException("TreeDataTemplate currently only supports Binding and CompiledBindingExtension!")
                 };
 
-                return InstancedBinding.OneWay(obs, BindingPriority.Style);
+                return new InstancedBinding(null, expression, BindingMode.OneWay, BindingPriority.Style);
             }
 
             return null;
diff --git a/src/Markup/Avalonia.Markup/Data/Binding.cs b/src/Markup/Avalonia.Markup/Data/Binding.cs
index 82e68e1ec..cdfc25d55 100644
--- a/src/Markup/Avalonia.Markup/Data/Binding.cs
+++ b/src/Markup/Avalonia.Markup/Data/Binding.cs
@@ -1,8 +1,14 @@
 using System;
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
+using Avalonia.Collections.Pooled;
 using Avalonia.Controls;
+using Avalonia.Data.Converters;
 using Avalonia.Data.Core;
+using Avalonia.Data.Core.ExpressionNodes;
+using Avalonia.Diagnostics;
 using Avalonia.Markup.Parsers;
+using Avalonia.Utilities;
 
 namespace Avalonia.Data
 {
@@ -43,7 +49,7 @@ namespace Avalonia.Data
         /// <summary>
         /// Gets or sets the source for the binding.
         /// </summary>
-        public object? Source { get; set; }
+        public object? Source { get; set; } = AvaloniaProperty.UnsetValue;
 
         /// <summary>
         /// Gets or sets the binding path.
@@ -55,85 +61,145 @@ namespace Avalonia.Data
         /// </summary>
         public Func<string?, string, Type>? TypeResolver { get; set; }
 
-        private protected override ExpressionObserver CreateExpressionObserver(AvaloniaObject target, AvaloniaProperty? targetProperty, object? anchor, bool enableDataValidation)
+        [Obsolete(ObsoletionMessages.MayBeRemovedInAvalonia12)]
+        public override InstancedBinding? Initiate(
+            AvaloniaObject target,
+            AvaloniaProperty? targetProperty,
+            object? anchor = null,
+            bool enableDataValidation = false)
         {
-            _ = target ?? throw new ArgumentNullException(nameof(target));
+            var expression = InstanceCore(targetProperty, target, anchor, enableDataValidation);
+            return new InstancedBinding(target, expression, Mode, Priority);
+        }
 
-            anchor ??= DefaultAnchor?.Target;
-            enableDataValidation = enableDataValidation && Priority == BindingPriority.LocalValue;
+        private protected override BindingExpressionBase Instance(
+            AvaloniaProperty targetProperty,
+            AvaloniaObject target,
+            object? anchor)
+        {
+            var enableDataValidation = targetProperty.GetMetadata(target.GetType()).EnableDataValidation ?? false;
+            return InstanceCore(targetProperty, target, anchor, enableDataValidation);
+        }
 
-            INameScope? nameScope = null;
-            NameScope?.TryGetTarget(out nameScope);
+        /// <summary>
+        /// Hack for TreeDataTemplate to create a binding expression for an item.
+        /// </summary>
+        /// <param name="source">The item.</param>
+        /// <remarks>
+        /// Ideally we'd do this in a more generic way but didn't have time to refactor
+        /// ITreeDataTemplate in time for 11.0. We should revisit this in 12.0.
+        /// </remarks>
+        // TODO12: Refactor
+        internal BindingExpression CreateObservableForTreeDataTemplate(object source)
+        {
+            if (!string.IsNullOrEmpty(ElementName))
+                throw new NotSupportedException("ElementName bindings are not supported in this context.");
+            if (RelativeSource is not null && RelativeSource.Mode != RelativeSourceMode.DataContext)
+                throw new NotSupportedException("RelativeSource bindings are not supported in this context.");
+            if (Source != AvaloniaProperty.UnsetValue)
+                throw new NotSupportedException("Source bindings are not supported in this context.");
 
-            var (node, mode) = ExpressionObserverBuilder.Parse(Path, enableDataValidation, TypeResolver, nameScope);
+            List<ExpressionNode>? nodes = null;
+            var isRooted = false;
 
-            if (node is null)
+            if (!string.IsNullOrEmpty(Path))
             {
-                throw new InvalidOperationException("Could not parse binding expression.");
+                var reader = new CharacterReader(Path.AsSpan());
+                var (astNodes, sourceMode) = BindingExpressionGrammar.ParseToPooledList(ref reader);
+                nodes = ExpressionNodeFactory.CreateFromAst(
+                    astNodes,
+                    TypeResolver,
+                    GetNameScope(),
+                    out isRooted);
             }
 
-            StyledElement GetSource()
+            if (isRooted)
+                throw new NotSupportedException("Rooted binding paths are not supported in this context.");
+
+            return new BindingExpression(
+                source,
+                nodes,
+                FallbackValue,
+                converter: Converter,
+                converterParameter: ConverterParameter,
+                targetNullValue: TargetNullValue);
+        }
+
+        private UntypedBindingExpressionBase InstanceCore(
+            AvaloniaProperty? targetProperty, 
+            AvaloniaObject target,
+            object? anchor,
+            bool enableDataValidation)
+        {
+            List<ExpressionNode>? nodes = null;
+            var isRooted = false;
+
+            // Build the expression nodes from the binding path.
+            if (!string.IsNullOrEmpty(Path))
             {
-                return target as StyledElement ??
-                    anchor as StyledElement ??
-                    throw new ArgumentException("Could not find binding source: either target or anchor must be an StyledElement.");
+                var reader = new CharacterReader(Path.AsSpan());
+                var (astPool, sourceMode) = BindingExpressionGrammar.ParseToPooledList(ref reader);
+                nodes = ExpressionNodeFactory.CreateFromAst(
+                    astPool,
+                    TypeResolver,
+                    GetNameScope(),
+                    out isRooted);
             }
 
-            if (ElementName != null)
+            // If the binding isn't rooted (i.e. doesn't have a Source or start with $parent, $self,
+            // #elementName etc.) then we need to add a source node. The type of source node will
+            // depend on the ElementName and RelativeSource properties of the binding and if
+            // neither of those are set will default to a data context node.
+            if (Source == AvaloniaProperty.UnsetValue && !isRooted && CreateSourceNode(targetProperty) is { } sourceNode)
             {
-                return CreateElementObserver(
-                    GetSource(),
-                    ElementName,
-                    node);
+                nodes ??= new();
+                nodes.Insert(0, sourceNode);
             }
-            else if (Source != null)
-            {
-                return CreateSourceObserver(Source, node);
-            }
-            else if (RelativeSource == null)
-            {
-                if (mode == SourceMode.Data)
-                {
-                    return CreateDataContextObserver(
-                        target,
-                        node,
-                        targetProperty == StyledElement.DataContextProperty,
-                        anchor);
-                }
-                else
-                {
-                    return CreateSourceObserver(GetSource(), node);
-                }
-            }
-            else if (RelativeSource.Mode == RelativeSourceMode.DataContext)
-            {
-                return CreateDataContextObserver(
-                    target,
-                    node,
-                    targetProperty == StyledElement.DataContextProperty,
-                    anchor);
-            }
-            else if (RelativeSource.Mode == RelativeSourceMode.Self)
-            {
-                return CreateSourceObserver(GetSource(), node);
-            }
-            else if (RelativeSource.Mode == RelativeSourceMode.TemplatedParent)
-            {
-                return CreateTemplatedParentObserver(GetSource(), node);
-            }
-            else if (RelativeSource.Mode == RelativeSourceMode.FindAncestor)
-            {
-                if (RelativeSource.Tree == TreeType.Visual && RelativeSource.AncestorType == null)
-                {
-                    throw new InvalidOperationException("AncestorType must be set for RelativeSourceMode.FindAncestor when searching the visual tree.");
-                }
 
-                return CreateFindAncestorObserver(GetSource(), RelativeSource, node);
-            }
-            else
+            // If the first node is an ISourceNode then allow it to select the source; otherwise
+            // use the binding source if specified, falling back to the target.
+            var source = nodes?.Count > 0 && nodes[0] is SourceNode sn ?
+                sn.SelectSource(Source, target, anchor ?? DefaultAnchor?.Target) :
+                Source != AvaloniaProperty.UnsetValue ? Source : target;
+
+            var (mode, trigger) = ResolveDefaultsFromMetadata(target, targetProperty);
+
+            return new BindingExpression(
+                source,
+                nodes,
+                FallbackValue,
+                converter: Converter,
+                converterCulture: ConverterCulture,
+                converterParameter: ConverterParameter,
+                enableDataValidation: enableDataValidation,
+                mode: mode,
+                priority: Priority,
+                stringFormat: StringFormat,
+                targetNullValue: TargetNullValue,
+                targetTypeConverter: TargetTypeConverter.GetReflectionConverter(),
+                updateSourceTrigger: trigger);
+        }
+
+        private INameScope? GetNameScope()
+        {
+            INameScope? result = null;
+            NameScope?.TryGetTarget(out result);
+            return result;
+        }
+
+        private ExpressionNode? CreateSourceNode(AvaloniaProperty? targetProperty)
+        {
+            if (!string.IsNullOrEmpty(ElementName))
             {
-                throw new NotSupportedException();
+                var nameScope = GetNameScope() ?? throw new InvalidOperationException(
+                    "Cannot create ElementName binding when NameScope is null");
+                return new NamedElementNode(nameScope, ElementName);
             }
+
+            if (RelativeSource is not null)
+                return ExpressionNodeFactory.CreateRelativeSource(RelativeSource);
+
+            return ExpressionNodeFactory.CreateDataContext(targetProperty);
         }
     }
 }
diff --git a/src/Markup/Avalonia.Markup/Data/BindingBase.cs b/src/Markup/Avalonia.Markup/Data/BindingBase.cs
index 129022aa2..21cb9a942 100644
--- a/src/Markup/Avalonia.Markup/Data/BindingBase.cs
+++ b/src/Markup/Avalonia.Markup/Data/BindingBase.cs
@@ -5,13 +5,11 @@ using System.Globalization;
 using Avalonia.Controls;
 using Avalonia.Data.Converters;
 using Avalonia.Data.Core;
-using Avalonia.LogicalTree;
-using Avalonia.Reactive;
-using Avalonia.VisualTree;
+using Avalonia.Diagnostics;
 
 namespace Avalonia.Data
 {
-    public abstract class BindingBase : IBinding
+    public abstract class BindingBase : IBinding, IBinding2
     {
         /// <summary>
         /// Initializes a new instance of the <see cref="Binding"/> class.
@@ -77,221 +75,52 @@ namespace Avalonia.Data
         /// </summary>
         public string? StringFormat { get; set; }
 
+        /// <summary>
+        /// Gets or sets a value that determines the timing of binding source updates for
+        /// <see cref="BindingMode.TwoWay"/> and <see cref="BindingMode.OneWayToSource"/> bindings.
+        /// </summary>
+        public UpdateSourceTrigger UpdateSourceTrigger { get; set; }
+
         public WeakReference? DefaultAnchor { get; set; }
 
         public WeakReference<INameScope?>? NameScope { get; set; }
 
-        private protected abstract ExpressionObserver CreateExpressionObserver(
-            AvaloniaObject target,
-            AvaloniaProperty? targetProperty,
-            object? anchor,
-            bool enableDataValidation);
-
         /// <inheritdoc/>
         [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = TrimmingMessages.TypeConversionSupressWarningMessage)]
-        public InstancedBinding? Initiate(
+        [Obsolete(ObsoletionMessages.MayBeRemovedInAvalonia12)]
+        public abstract InstancedBinding? Initiate(
             AvaloniaObject target,
             AvaloniaProperty? targetProperty,
             object? anchor = null,
-            bool enableDataValidation = false)
-        {
-            _ = target ?? throw new ArgumentNullException(nameof(target));
+            bool enableDataValidation = false);
 
-            anchor = anchor ?? DefaultAnchor?.Target;
-
-            enableDataValidation = enableDataValidation && Priority == BindingPriority.LocalValue;
-
-            var observer = CreateExpressionObserver(target, targetProperty, anchor, enableDataValidation);
-
-            var fallback = FallbackValue;
-
-            // If we're binding to DataContext and our fallback is UnsetValue then override
-            // the fallback value to null, as broken bindings to DataContext must reset the
-            // DataContext in order to not propagate incorrect DataContexts to child controls.
-            // See Avalonia.Markup.UnitTests.Data.DataContext_Binding_Should_Produce_Correct_Results.
-            if (targetProperty == StyledElement.DataContextProperty && fallback == AvaloniaProperty.UnsetValue)
-            {
-                fallback = null;
-            }
-
-            var converter = Converter;
-            var targetType = targetProperty?.PropertyType ?? typeof(object);
-
-            // We only respect `StringFormat` if the type of the property we're assigning to will
-            // accept a string. Note that this is slightly different to WPF in that WPF only applies
-            // `StringFormat` for target type `string` (not `object`).
-            if (!string.IsNullOrWhiteSpace(StringFormat) &&
-                (targetType == typeof(string) || targetType == typeof(object)))
-            {
-                converter = new StringFormatValueConverter(StringFormat!, converter);
-            }
-
-            var subject = new BindingExpression(
-                observer,
-                targetType,
-                fallback,
-                TargetNullValue,
-                converter ?? DefaultValueConverter.Instance,
-                ConverterCulture ?? CultureInfo.CurrentCulture,
-                ConverterParameter,
-                Priority);
-
-            return new InstancedBinding(subject, Mode, Priority);
-        }
-
-        private protected ExpressionObserver CreateDataContextObserver(
+        private protected abstract BindingExpressionBase Instance(
+            AvaloniaProperty targetProperty,
             AvaloniaObject target,
-            ExpressionNode node,
-            bool targetIsDataContext,
-            object? anchor)
-        {
-            _ = target ?? throw new ArgumentNullException(nameof(target));
+            object? anchor);
 
-            if (target is not IDataContextProvider)
+        private protected (BindingMode, UpdateSourceTrigger) ResolveDefaultsFromMetadata(
+            AvaloniaObject target,
+            AvaloniaProperty? targetProperty)
+        {
+            var mode = Mode;
+            var trigger = UpdateSourceTrigger == UpdateSourceTrigger.Default ?
+                UpdateSourceTrigger.PropertyChanged : UpdateSourceTrigger;
+
+            if (mode == BindingMode.Default)
             {
-                if (anchor is IDataContextProvider && anchor is AvaloniaObject ao)
-                    target = ao;
+                if (targetProperty?.GetMetadata(target.GetType()) is { } metadata)
+                    mode = metadata.DefaultBindingMode;
                 else
-                    throw new InvalidOperationException("Cannot find a DataContext to bind to.");
+                    mode = BindingMode.OneWay;
             }
 
-            if (!targetIsDataContext)
-            {
-                var result = new ExpressionObserver(
-                    () => target.GetValue(StyledElement.DataContextProperty),
-                    node,
-                    new UpdateSignal(target, StyledElement.DataContextProperty),
-                    null);
-
-                return result;
-            }
-            else
-            {
-                return new ExpressionObserver(
-                    GetParentDataContext(target),
-                    node,
-                    null);
-            }
+            return (mode, trigger);
         }
 
-        private protected ExpressionObserver CreateElementObserver(
-            StyledElement target,
-            string elementName,
-            ExpressionNode node)
+        BindingExpressionBase IBinding2.Instance(AvaloniaObject target, AvaloniaProperty property, object? anchor)
         {
-            _ = target ?? throw new ArgumentNullException(nameof(target));
-
-            if (NameScope is null || !NameScope.TryGetTarget(out var scope))
-                throw new InvalidOperationException("Name scope is null or was already collected");
-            var result = new ExpressionObserver(
-                NameScopeLocator.Track(scope, elementName),
-                node,
-                null);
-            return result;
-        }
-
-        private protected ExpressionObserver CreateFindAncestorObserver(
-            StyledElement target,
-            RelativeSource relativeSource,
-            ExpressionNode node)
-        {
-            _ = target ?? throw new ArgumentNullException(nameof(target));
-
-            IObservable<object?> controlLocator;
-
-            switch (relativeSource.Tree)
-            {
-                case TreeType.Logical:
-                    controlLocator = ControlLocator.Track(
-                        (ILogical)target,
-                        relativeSource.AncestorLevel - 1,
-                        relativeSource.AncestorType);
-                    break;
-                case TreeType.Visual:
-                    controlLocator = VisualLocator.Track(
-                        (Visual)target,
-                        relativeSource.AncestorLevel - 1,
-                        relativeSource.AncestorType);
-                    break;
-                default:
-                    throw new InvalidOperationException("Invalid tree to traverse.");
-            }
-
-            return new ExpressionObserver(
-                controlLocator,
-                node,
-                null);
-        }
-
-        private protected ExpressionObserver CreateSourceObserver(
-            object source,
-            ExpressionNode node)
-        {
-            _ = source ?? throw new ArgumentNullException(nameof(source));
-
-            return new ExpressionObserver(source, node);
-        }
-
-        private protected ExpressionObserver CreateTemplatedParentObserver(
-            AvaloniaObject target,
-            ExpressionNode node)
-        {
-            _ = target ?? throw new ArgumentNullException(nameof(target));
-
-            var result = new ExpressionObserver(
-                () => target.GetValue(StyledElement.TemplatedParentProperty),
-                node,
-                new UpdateSignal(target, StyledElement.TemplatedParentProperty),
-                null);
-
-            return result;
-        }
-
-        private IObservable<object?> GetParentDataContext(AvaloniaObject target)
-        {
-            // The DataContext is based on the visual parent and not the logical parent: this may
-            // seem counter intuitive considering the fact that property inheritance works on the logical
-            // tree, but consider a ContentControl with a ContentPresenter. The ContentControl's
-            // Content property is bound to a value which becomes the ContentPresenter's 
-            // DataContext - it is from this that the child hosted by the ContentPresenter needs to
-            // inherit its DataContext.
-
-            return target.GetObservable(Visual.VisualParentProperty)
-                .Select(x =>
-                {
-                    return (x as AvaloniaObject)?.GetObservable(StyledElement.DataContextProperty) ??
-                           Observable.Return((object?)null);
-                }).Switch();
-        }
-
-        private class UpdateSignal : SingleSubscriberObservableBase<ValueTuple>
-        {
-            private readonly AvaloniaObject _target;
-            private readonly AvaloniaProperty _property;
-
-            public UpdateSignal(AvaloniaObject target, AvaloniaProperty property)
-            {
-                _target = target;
-                _property = property;
-            }
-
-            protected override void Subscribed()
-            {
-                _target.PropertyChanged += PropertyChanged;
-            }
-
-            protected override void Unsubscribed()
-            {
-                _target.PropertyChanged -= PropertyChanged;
-            }
-
-            private void PropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
-            {
-                if (e.Property == _property)
-                {
-                    PublishNext(default);
-                }
-            }
+            return Instance(property, target, anchor);
         }
     }
 }
diff --git a/src/Markup/Avalonia.Markup/Data/MultiBinding.cs b/src/Markup/Avalonia.Markup/Data/MultiBinding.cs
index 993f63b4d..044dfb4a4 100644
--- a/src/Markup/Avalonia.Markup/Data/MultiBinding.cs
+++ b/src/Markup/Avalonia.Markup/Data/MultiBinding.cs
@@ -5,13 +5,14 @@ using System.Linq;
 using Avalonia.Reactive;
 using Avalonia.Data.Converters;
 using Avalonia.Metadata;
+using Avalonia.Data.Core;
 
 namespace Avalonia.Data
 {
     /// <summary>
     /// A XAML binding that calculates an aggregate value from multiple child <see cref="Bindings"/>.
     /// </summary>
-    public class MultiBinding : IBinding
+    public class MultiBinding : IBinding2
     {
         /// <summary>
         /// Gets the collection of child bindings.
@@ -72,25 +73,7 @@ namespace Avalonia.Data
             object? anchor = null,
             bool enableDataValidation = false)
         {
-            var targetType = targetProperty?.PropertyType ?? typeof(object);
-            var converter = Converter;
-            // We only respect `StringFormat` if the type of the property we're assigning to will
-            // accept a string. Note that this is slightly different to WPF in that WPF only applies
-            // `StringFormat` for target type `string` (not `object`).
-            if (!string.IsNullOrWhiteSpace(StringFormat) &&
-                (targetType == typeof(string) || targetType == typeof(object)))
-            {
-                converter = new StringFormatMultiValueConverter(StringFormat!, converter);
-            }
-
-            var children = Bindings.Select(x => x.Initiate(target, null));
-
-            var input = children.Select(x => x?.Source)
-                                .Where(x => x is not null)!
-                                .CombineLatest()
-                                .Select(x => ConvertValue(x, targetType, converter))
-                                .Where(x => x != BindingOperations.DoNothing);
-
+            var input = InstanceCore(target, targetProperty);
             var mode = Mode == BindingMode.Default ?
                 targetProperty?.GetMetadata(target.GetType()).DefaultBindingMode : Mode;
 
@@ -106,6 +89,35 @@ namespace Avalonia.Data
             }
         }
 
+        BindingExpressionBase IBinding2.Instance(AvaloniaObject target, AvaloniaProperty property, object? anchor)
+        {
+            // TODO: Implement MultiBindingExpression instead of wrapping an observable.
+            var o = InstanceCore(target, property);
+            return new UntypedObservableBindingExpression(o, BindingPriority.LocalValue);
+        }
+
+        private IObservable<object?> InstanceCore(AvaloniaObject target, AvaloniaProperty? targetProperty)
+        {
+            var targetType = targetProperty?.PropertyType ?? typeof(object);
+            var converter = Converter;
+            // We only respect `StringFormat` if the type of the property we're assigning to will
+            // accept a string. Note that this is slightly different to WPF in that WPF only applies
+            // `StringFormat` for target type `string` (not `object`).
+            if (!string.IsNullOrWhiteSpace(StringFormat) &&
+                (targetType == typeof(string) || targetType == typeof(object)))
+            {
+                converter = new StringFormatMultiValueConverter(StringFormat!, converter);
+            }
+
+            var children = Bindings.Select(x => x.Initiate(target, null));
+
+            return children.Select(x => x?.Source)
+                .Where(x => x is not null)!
+                .CombineLatest()
+                .Select(x => ConvertValue(x, targetType, converter))
+                .Where(x => x != BindingOperations.DoNothing);
+        }
+
         private object ConvertValue(IList<object?> values, Type targetType, IMultiValueConverter? converter)
         {
             for (var i = 0; i < values.Count; ++i)
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/BindingExpressionGrammar.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/BindingExpressionGrammar.cs
index 12440e945..5a4a56b74 100644
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/BindingExpressionGrammar.cs
+++ b/src/Markup/Avalonia.Markup/Markup/Parsers/BindingExpressionGrammar.cs
@@ -16,9 +16,26 @@ namespace Avalonia.Markup.Parsers
 
     internal static class BindingExpressionGrammar
     {
+        private static readonly List<INode> s_pool = new();
+
         public static (List<INode> Nodes, SourceMode Mode) Parse(ref CharacterReader r)
         {
-            var nodes = new List<INode>();
+            var result = new List<INode>();
+            var mode = Parse(ref r, result);
+            return (result, mode);
+        }
+
+        public static (List<INode> Nodes, SourceMode Mode) ParseToPooledList(ref CharacterReader r)
+        {
+            // Most of the time the list will be passed to `ExpressionNodeFactory.CreateFromAst`
+            // and then discarded so as a micro-optimization we can reuse the list.
+            s_pool.Clear();
+            var mode = Parse(ref r, s_pool);
+            return (s_pool, mode);
+        }
+
+        private static SourceMode Parse(ref CharacterReader r, List<INode> nodes)
+        {
             var state = State.Start;
             var mode = SourceMode.Data;
 
@@ -62,12 +79,17 @@ namespace Avalonia.Markup.Parsers
                 }
             }
 
+            if (!r.End)
+            {
+                throw new ExpressionParseException(r.Position, "Expected end of expression.");
+            }
+
             if (state == State.BeforeMember)
             {
                 throw new ExpressionParseException(r.Position, "Unexpected end of expression.");
             }
 
-            return (nodes, mode);
+            return mode;
         }
 
         private static State ParseStart(ref CharacterReader r, IList<INode> nodes)
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionNodeFactory.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionNodeFactory.cs
new file mode 100644
index 000000000..1db39362d
--- /dev/null
+++ b/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionNodeFactory.cs
@@ -0,0 +1,145 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using Avalonia.Controls;
+using Avalonia.Data;
+using Avalonia.Data.Core.ExpressionNodes;
+using Avalonia.Data.Core.ExpressionNodes.Reflection;
+
+namespace Avalonia.Markup.Parsers
+{
+    /// <summary>
+    /// Creates <see cref="ExpressionNode"/>s from a <see cref="BindingExpressionGrammar"/>.
+    /// </summary>
+    internal static class ExpressionNodeFactory
+    {
+        [RequiresUnreferencedCode(TrimmingMessages.ReflectionBindingRequiresUnreferencedCodeMessage)]
+        public static List<ExpressionNode>? CreateFromAst(
+            List<BindingExpressionGrammar.INode> astNodes,
+            Func<string?, string, Type>? typeResolver,
+            INameScope? nameScope,
+            out bool isRooted)
+        {
+            var negated = 0;
+            List<ExpressionNode>? result = null;
+            ExpressionNode? node = null;
+
+            isRooted = false;
+
+            foreach (var astNode in astNodes)
+            {
+                switch (astNode)
+                {
+                    case BindingExpressionGrammar.AncestorNode ancestor:
+                        node = LogicalAncestorNode(typeResolver, ancestor);
+                        isRooted = true;
+                        break;
+                    case BindingExpressionGrammar.AttachedPropertyNameNode attached:
+                        node = AttachedPropertyNode(typeResolver, attached);
+                        break;
+                    case BindingExpressionGrammar.EmptyExpressionNode:
+                        node = null;
+                        break;
+                    case BindingExpressionGrammar.IndexerNode indexer:
+                        node = new ReflectionIndexerNode((IList)indexer.Arguments);
+                        break;
+                    case BindingExpressionGrammar.NameNode name:
+                        node = new NamedElementNode(nameScope, name.Name);
+                        isRooted = true;
+                        break;
+                    case BindingExpressionGrammar.NotNode:
+                        ++negated;
+                        break;
+                    case BindingExpressionGrammar.PropertyNameNode propName:
+                        node = new DynamicPluginPropertyAccessorNode(propName.PropertyName);
+                        break;
+                    case BindingExpressionGrammar.SelfNode:
+                        node = null;
+                        isRooted = true;
+                        break;
+                    case BindingExpressionGrammar.StreamNode:
+                        node = new DynamicPluginStreamNode();
+                        break;
+                    case BindingExpressionGrammar.TypeCastNode typeCast:
+                        node = new ReflectionTypeCastNode(LookupType(typeResolver, typeCast.Namespace, typeCast.TypeName));
+                        break;
+                    default:
+                        throw new Exception($"Unexpected node type '{astNode}'.");
+                }
+
+                if (node is not null)
+                {
+                    result ??= new(astNodes.Count);
+                    result.Add(node);
+                }
+            }
+
+            if (negated != 0)
+            {
+                result ??= new(negated);
+                for (var i = 0; i < negated; ++i)
+                    result.Add(new LogicalNotNode());
+            }
+
+            return result;
+        }
+
+        public static ExpressionNode? CreateRelativeSource(RelativeSource source)
+        {
+            return source.Mode switch
+            {
+                RelativeSourceMode.DataContext => new DataContextNode(),
+                RelativeSourceMode.TemplatedParent => new TemplatedParentNode(),
+                RelativeSourceMode.Self => null,
+                RelativeSourceMode.FindAncestor when source.Tree == TreeType.Logical =>
+                    new LogicalAncestorElementNode(source.AncestorType, source.AncestorLevel - 1),
+                RelativeSourceMode.FindAncestor when source.Tree == TreeType.Visual =>
+                    new VisualAncestorElementNode(source.AncestorType, source.AncestorLevel - 1),
+                _ => throw new NotSupportedException("Unsupported RelativeSource mode.")
+            };
+        }
+
+        public static ExpressionNode CreateDataContext(AvaloniaProperty? targetProperty)
+        {
+            return targetProperty == StyledElement.DataContextProperty ? 
+                new ParentDataContextNode() :
+                new DataContextNode();
+        }
+
+        private static AvaloniaPropertyAccessorNode AttachedPropertyNode(
+            Func<string?, string, Type>? typeResolver,
+            BindingExpressionGrammar.AttachedPropertyNameNode attached)
+        {
+            var type = LookupType(typeResolver, attached.Namespace, attached.TypeName);
+            var property = AvaloniaPropertyRegistry.Instance.FindRegistered(type, attached.PropertyName) ??
+                throw new InvalidOperationException($"Cannot find property {type}.{attached.PropertyName}.");
+            return new AvaloniaPropertyAccessorNode(property);
+        }
+
+        private static LogicalAncestorElementNode LogicalAncestorNode(
+            Func<string?, string, Type>? typeResolver,
+            BindingExpressionGrammar.AncestorNode ancestor)
+        {
+            Type? type = null;
+
+            if (!string.IsNullOrEmpty(ancestor.TypeName))
+            {
+                type = LookupType(typeResolver, ancestor.Namespace, ancestor.TypeName);
+            }
+
+            return new LogicalAncestorElementNode(type, ancestor.Level);
+        }
+
+        private static Type LookupType(
+            Func<string?, string, Type>? typeResolver,
+            string? @namespace,
+            string? name)
+        {
+            if (name is null)
+                throw new InvalidOperationException($"Unable to resolve unnamed type from namespace '{@namespace}'.");
+            return typeResolver?.Invoke(@namespace, name) ??
+                throw new InvalidOperationException($"Unable to resolve type '{@namespace}:{name}'.");
+        }
+    }
+}
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionObserverBuilder.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionObserverBuilder.cs
deleted file mode 100644
index 9615057b2..000000000
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionObserverBuilder.cs
+++ /dev/null
@@ -1,80 +0,0 @@
-using System;
-using System.Diagnostics.CodeAnalysis;
-using Avalonia.Controls;
-using Avalonia.Data.Core;
-using Avalonia.Utilities;
-
-namespace Avalonia.Markup.Parsers
-{
-    internal static class ExpressionObserverBuilder
-    {
-        [RequiresUnreferencedCode(TrimmingMessages.ReflectionBindingRequiresUnreferencedCodeMessage)]
-        internal static (ExpressionNode Node, SourceMode Mode) Parse(string expression, bool enableValidation = false, Func<string?, string, Type>? typeResolver = null,
-            INameScope? nameScope = null)
-        {
-            if (string.IsNullOrWhiteSpace(expression))
-            {
-                return (new EmptyExpressionNode(), default);
-            }
-            
-            var reader = new CharacterReader(expression.AsSpan());
-            var parser = new ExpressionParser(enableValidation, typeResolver, nameScope);
-            var node = parser.Parse(ref reader);
-
-            if (!reader.End)
-            {
-                throw new ExpressionParseException(reader.Position, "Expected end of expression.");
-            }
-
-            return node;
-        }
-
-        [RequiresUnreferencedCode(TrimmingMessages.ReflectionBindingRequiresUnreferencedCodeMessage)]
-        public static ExpressionObserver Build(
-            object root,
-            string expression,
-            bool enableDataValidation = false,
-            string? description = null,
-            Func<string?, string, Type>? typeResolver = null)
-        {
-            return new ExpressionObserver(
-                root,
-                Parse(expression, enableDataValidation, typeResolver).Node,
-                description ?? expression);
-        }
-
-        [RequiresUnreferencedCode(TrimmingMessages.ReflectionBindingRequiresUnreferencedCodeMessage)]
-        public static ExpressionObserver Build(
-            IObservable<object> rootObservable,
-            string expression,
-            bool enableDataValidation = false,
-            string? description = null,
-            Func<string?, string, Type>? typeResolver = null)
-        {
-            _ = rootObservable ?? throw new ArgumentNullException(nameof(rootObservable));
-
-            return new ExpressionObserver(
-                rootObservable,
-                Parse(expression, enableDataValidation, typeResolver).Node,
-                description ?? expression);
-        }
-
-        [RequiresUnreferencedCode(TrimmingMessages.ReflectionBindingRequiresUnreferencedCodeMessage)]
-        public static ExpressionObserver Build(
-            Func<object> rootGetter,
-            string expression,
-            IObservable<ValueTuple> update,
-            bool enableDataValidation = false,
-            string? description = null,
-            Func<string?, string, Type>? typeResolver = null)
-        {
-            _ = rootGetter ?? throw new ArgumentNullException(nameof(rootGetter));
-
-            return new ExpressionObserver(
-                rootGetter,
-                Parse(expression, enableDataValidation, typeResolver).Node,
-                update,
-                description ?? expression);
-        }
-    }
-}
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionParser.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionParser.cs
deleted file mode 100644
index 8124d73a3..000000000
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionParser.cs
+++ /dev/null
@@ -1,139 +0,0 @@
-using Avalonia.Data.Core;
-using Avalonia.Markup.Parsers.Nodes;
-using Avalonia.Utilities;
-using System;
-using Avalonia.Controls;
-using System.Diagnostics.CodeAnalysis;
-
-namespace Avalonia.Markup.Parsers
-{
-    /// <summary>
-    /// Parser for composition expressions
-    /// </summary>
-    internal class ExpressionParser
-    {
-        private readonly bool _enableValidation;
-        private readonly Func<string?, string, Type>? _typeResolver;
-        private readonly INameScope? _nameScope;
-
-        public ExpressionParser(bool enableValidation, Func<string?, string, Type>? typeResolver, INameScope? nameScope)
-        {
-            _typeResolver = typeResolver;
-            _nameScope = nameScope;
-            _enableValidation = enableValidation;
-        }
-
-        [RequiresUnreferencedCode(TrimmingMessages.ReflectionBindingRequiresUnreferencedCodeMessage)]
-        public (ExpressionNode Node, SourceMode Mode) Parse(ref CharacterReader r)
-        {
-            ExpressionNode? rootNode = null;
-            ExpressionNode? node = null;
-            var (astNodes, mode) = BindingExpressionGrammar.Parse(ref r);
-
-            foreach (var astNode in astNodes)
-            {
-                ExpressionNode? nextNode = null;
-                switch (astNode)
-                {
-                    case BindingExpressionGrammar.EmptyExpressionNode:
-                        nextNode = new EmptyExpressionNode();
-                        break;
-                    case BindingExpressionGrammar.NotNode:
-                        nextNode = new LogicalNotNode();
-                        break;
-                    case BindingExpressionGrammar.StreamNode:
-                        nextNode = new StreamNode();
-                        break;
-                    case BindingExpressionGrammar.PropertyNameNode propName:
-                        nextNode = new PropertyAccessorNode(propName.PropertyName, _enableValidation);
-                        break;
-                    case BindingExpressionGrammar.IndexerNode indexer:
-                        nextNode = new StringIndexerNode(indexer.Arguments);
-                        break;
-                    case BindingExpressionGrammar.AttachedPropertyNameNode attachedProp:
-                        nextNode = ParseAttachedProperty(attachedProp);
-                        break;
-                    case BindingExpressionGrammar.SelfNode:
-                        nextNode = new SelfNode();
-                        break;
-                    case BindingExpressionGrammar.AncestorNode ancestor:
-                        nextNode = ParseFindAncestor(ancestor);
-                        break;
-                    case BindingExpressionGrammar.NameNode elementName:
-                        nextNode = new ElementNameNode(_nameScope ?? throw new NotSupportedException("Invalid element name binding with null name scope!"), elementName.Name);
-                        break;
-                    case BindingExpressionGrammar.TypeCastNode typeCast:
-                        nextNode = ParseTypeCastNode(typeCast);
-                        break;
-                }
-                if (node is null)
-                {
-                    rootNode = node = nextNode;
-                }
-                else
-                {
-                    node.Next = nextNode;
-                    node = nextNode;
-                }
-            }
-
-            if (rootNode is null)
-                throw new ExpressionParseException(r.Position, "Unexpected end of expression.");
-
-            return (rootNode, mode);
-        }
-
-        private FindAncestorNode ParseFindAncestor(BindingExpressionGrammar.AncestorNode node)
-        {
-            Type? ancestorType = null;
-            var ancestorLevel = node.Level;
-
-            if (!string.IsNullOrEmpty(node.TypeName))
-            {
-                if (_typeResolver == null)
-                {
-                    throw new InvalidOperationException("Cannot parse a binding path with a typed FindAncestor without a type resolver. Maybe you can use a LINQ Expression binding path instead?");
-                }
-
-                ancestorType = _typeResolver(node.Namespace, node.TypeName);
-            }
-
-            return new FindAncestorNode(ancestorType, ancestorLevel);
-        }
-
-        private TypeCastNode ParseTypeCastNode(BindingExpressionGrammar.TypeCastNode node)
-        {
-            Type? castType = null;
-            if (!string.IsNullOrEmpty(node.TypeName))
-            {
-                if (_typeResolver == null)
-                {
-                    throw new InvalidOperationException("Cannot parse a binding path with a typed Cast without a type resolver. Maybe you can use a LINQ Expression binding path instead?");
-                }
-
-                castType = _typeResolver(node.Namespace, node.TypeName);
-            }
-
-            if (castType is null)
-                throw new InvalidOperationException("Unable to determine type for cast.");
-
-            return new TypeCastNode(castType);
-        }
-
-        private AvaloniaPropertyAccessorNode ParseAttachedProperty(BindingExpressionGrammar.AttachedPropertyNameNode node)
-        {
-            if (_typeResolver == null)
-            {
-                throw new InvalidOperationException("Cannot parse a binding path with an attached property without a type resolver. Maybe you can use a LINQ Expression binding path instead?");
-            }
-
-            var type = _typeResolver(node.Namespace, node.TypeName);
-            var property = AvaloniaPropertyRegistry.Instance.FindRegistered(type, node.PropertyName);
-
-            if (property is null)
-                throw new InvalidOperationException($"Cannot find property {type}.{node.PropertyName}.");
-
-            return new AvaloniaPropertyAccessorNode(property, _enableValidation);
-        }
-    }
-}
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/ElementNameNode.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/ElementNameNode.cs
deleted file mode 100644
index e676c7487..000000000
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/ElementNameNode.cs
+++ /dev/null
@@ -1,37 +0,0 @@
-using System;
-using Avalonia.Controls;
-using Avalonia.Data.Core;
-using Avalonia.LogicalTree;
-using Avalonia.Reactive;
-
-namespace Avalonia.Markup.Parsers.Nodes
-{
-    internal class ElementNameNode : ExpressionNode
-    {
-        private readonly WeakReference<INameScope> _nameScope;
-        private readonly string _name;
-        private IDisposable? _subscription;
-
-        public ElementNameNode(INameScope nameScope, string name)
-        {
-            _nameScope = new WeakReference<INameScope>(nameScope);
-            _name = name;
-        }
-
-        public override string Description => $"#{_name}";
-
-        protected override void StartListeningCore(WeakReference<object?> reference)
-        {
-            if (_nameScope.TryGetTarget(out var scope))
-                _subscription = NameScopeLocator.Track(scope, _name).Subscribe(ValueChanged);
-            else
-                _subscription = null;
-        }
-
-        protected override void StopListeningCore()
-        {
-            _subscription?.Dispose();
-            _subscription = null;
-        }
-    }
-}
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/FindAncestorNode.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/FindAncestorNode.cs
deleted file mode 100644
index 383a16081..000000000
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/FindAncestorNode.cs
+++ /dev/null
@@ -1,53 +0,0 @@
-using System;
-using Avalonia.Data.Core;
-using Avalonia.LogicalTree;
-using Avalonia.Reactive;
-
-namespace Avalonia.Markup.Parsers.Nodes
-{
-    internal class FindAncestorNode : ExpressionNode
-    {
-        private readonly int _level;
-        private readonly Type? _ancestorType;
-        private IDisposable? _subscription;
-
-        public FindAncestorNode(Type? ancestorType, int level)
-        {
-            _level = level;
-            _ancestorType = ancestorType;
-        }
-
-        public override string Description
-        {
-            get
-            {
-                if (_ancestorType == null)
-                {
-                    return $"$parent[{_level}]";
-                }
-                else
-                {
-                    return $"$parent[{_ancestorType.Name}, {_level}]";
-                }
-            }
-        }
-
-        protected override void StartListeningCore(WeakReference<object?> reference)
-        {
-            if (reference.TryGetTarget(out var target) && target is ILogical logical)
-            {
-                _subscription = ControlLocator.Track(logical, _level, _ancestorType).Subscribe(ValueChanged);
-            }
-            else
-            {
-                _subscription = null;
-            }
-        }
-
-        protected override void StopListeningCore()
-        {
-            _subscription?.Dispose();
-            _subscription = null;
-        }
-    }
-}
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/SelfNode.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/SelfNode.cs
deleted file mode 100644
index 2cb87efa6..000000000
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/SelfNode.cs
+++ /dev/null
@@ -1,9 +0,0 @@
-using Avalonia.Data.Core;
-
-namespace Avalonia.Markup.Parsers.Nodes
-{
-    internal class SelfNode : ExpressionNode
-    {
-        public override string Description => "$self";
-    }
-}
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/StringIndexerNode.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/StringIndexerNode.cs
deleted file mode 100644
index ba1c1edff..000000000
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/StringIndexerNode.cs
+++ /dev/null
@@ -1,317 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.ComponentModel;
-using System.Diagnostics.CodeAnalysis;
-using System.Globalization;
-using System.Linq;
-using Avalonia.Reactive;
-using System.Reflection;
-using Avalonia.Data;
-using Avalonia.Data.Core;
-using Avalonia.Utilities;
-
-namespace Avalonia.Markup.Parsers.Nodes
-{
-    [RequiresUnreferencedCode(TrimmingMessages.ReflectionBindingRequiresUnreferencedCodeMessage)]
-    internal class StringIndexerNode : IndexerNodeBase
-    {
-        public StringIndexerNode(IList<string> arguments)
-        {
-            Arguments = arguments;
-        }
-
-        public override string Description => "[" + string.Join(",", Arguments) + "]";
-
-        protected override bool SetTargetValueCore(object? value, BindingPriority priority)
-        {
-            if (!Target.TryGetTarget(out var target) || target is null)
-                return false;
-
-            var typeInfo = target.GetType().GetTypeInfo();
-            var list = target as IList;
-            var dictionary = target as IDictionary;
-            var indexerProperty = GetIndexer(typeInfo);
-            ParameterInfo[] indexerParameters;
-
-            if (indexerProperty != null && (indexerParameters = indexerProperty.GetIndexParameters()).Length == Arguments.Count)
-            {
-                var convertedObjectArray = new object[indexerParameters.Length];
-
-                for (int i = 0; i < Arguments.Count; i++)
-                {
-                    object? temp = null;
-
-                    if (!TypeUtilities.TryConvert(indexerParameters[i].ParameterType, Arguments[i], CultureInfo.InvariantCulture, out temp))
-                    {
-                        return false;
-                    }
-
-                    convertedObjectArray[i] = temp!;
-                }
-
-                var intArgs = convertedObjectArray.OfType<int>().ToArray();
-
-                // Try special cases where we can validate indices
-                if (typeInfo.IsArray)
-                {
-                    return SetValueInArray((Array)target, intArgs, value);
-                }
-                else if (Arguments.Count == 1)
-                {
-                    if (list != null)
-                    {
-                        if (intArgs.Length == Arguments.Count && intArgs[0] >= 0 && intArgs[0] < list.Count)
-                        {
-                            list[intArgs[0]] = value;
-                            return true;
-                        }
-
-                        return false;
-                    }
-                    else if (dictionary != null)
-                    {
-                        if (dictionary.Contains(convertedObjectArray[0]))
-                        {
-                            dictionary[convertedObjectArray[0]] = value;
-                            return true;
-                        }
-                        else
-                        {
-                            dictionary.Add(convertedObjectArray[0], value);
-                            return true;
-                        }
-                    }
-                    else
-                    {
-                        // Fallback to unchecked access
-                        indexerProperty.SetValue(target, value, convertedObjectArray);
-                        return true;
-                    }
-                }
-                else
-                {
-                    // Fallback to unchecked access
-                    indexerProperty.SetValue(target, value, convertedObjectArray);
-                    return true;
-                }
-            }
-            // Multidimensional arrays end up here because the indexer search picks up the IList indexer instead of the
-            // multidimensional indexer, which doesn't take the same number of arguments
-            else if (typeInfo.IsArray)
-            {
-                SetValueInArray((Array)target, value);
-                return true;
-            }
-            return false;
-        }
-
-        private bool SetValueInArray(Array array, object? value)
-        {
-            int[] intArgs;
-            if (!ConvertArgumentsToInts(out intArgs))
-                return false;
-            return SetValueInArray(array, intArgs);
-        }
-
-
-        private static bool SetValueInArray(Array array, int[] indices, object? value)
-        {
-            if (ValidBounds(indices, array))
-            {
-                array.SetValue(value, indices);
-                return true;
-            }
-            return false;
-        }
-
-
-        public IList<string> Arguments { get; }
-
-        public override Type? PropertyType
-        {
-            get
-            {
-                if (!Target.TryGetTarget(out var target) || target is null)
-                {
-                    return null;
-                }
-
-                return GetIndexer(target.GetType().GetTypeInfo())?.PropertyType;
-            }
-        }
-
-        protected override object? GetValue(object? target)
-        {
-            if (target is null)
-                return null;
-
-            var typeInfo = target.GetType().GetTypeInfo();
-            var list = target as IList;
-            var dictionary = target as IDictionary;
-            var indexerProperty = GetIndexer(typeInfo);
-            ParameterInfo[] indexerParameters;
-
-            if (indexerProperty != null && (indexerParameters = indexerProperty.GetIndexParameters()).Length == Arguments.Count)
-            {
-                var convertedObjectArray = new object[indexerParameters.Length];
-
-                for (int i = 0; i < Arguments.Count; i++)
-                {
-                    object? temp = null;
-
-                    if (!TypeUtilities.TryConvert(indexerParameters[i].ParameterType, Arguments[i], CultureInfo.InvariantCulture, out temp))
-                    {
-                        return AvaloniaProperty.UnsetValue;
-                    }
-
-                    convertedObjectArray[i] = temp!;
-                }
-
-                var intArgs = convertedObjectArray.OfType<int>().ToArray();
-
-                // Try special cases where we can validate indices
-                if (typeInfo.IsArray)
-                {
-                    return GetValueFromArray((Array)target, intArgs);
-                }
-                else if (Arguments.Count == 1)
-                {
-                    if (list != null)
-                    {
-                        if (intArgs.Length == Arguments.Count && intArgs[0] >= 0 && intArgs[0] < list.Count)
-                        {
-                            return list[intArgs[0]];
-                        }
-
-                        return AvaloniaProperty.UnsetValue;
-                    }
-                    else if (dictionary != null)
-                    {
-                        if (dictionary.Contains(convertedObjectArray[0]))
-                        {
-                            return dictionary[convertedObjectArray[0]];
-                        }
-
-                        return AvaloniaProperty.UnsetValue;
-                    }
-                    else
-                    {
-                        // Fallback to unchecked access
-                        return indexerProperty.GetValue(target, convertedObjectArray);
-                    }
-                }
-                else
-                {
-                    // Fallback to unchecked access
-                    return indexerProperty.GetValue(target, convertedObjectArray);
-                }
-            }
-            // Multidimensional arrays end up here because the indexer search picks up the IList indexer instead of the
-            // multidimensional indexer, which doesn't take the same number of arguments
-            else if (typeInfo.IsArray)
-            {
-                return GetValueFromArray((Array)target);
-            }
-
-            return AvaloniaProperty.UnsetValue;
-        }
-
-        private object? GetValueFromArray(Array array)
-        {
-            int[] intArgs;
-            if (!ConvertArgumentsToInts(out intArgs))
-                return AvaloniaProperty.UnsetValue;
-            return GetValueFromArray(array, intArgs);
-        }
-
-        private static object? GetValueFromArray(Array array, int[] indices)
-        {
-            if (ValidBounds(indices, array))
-            {
-                return array.GetValue(indices);
-            }
-            return AvaloniaProperty.UnsetValue;
-        }
-
-        private bool ConvertArgumentsToInts(out int[] intArgs)
-        {
-            intArgs = new int[Arguments.Count];
-
-            for (int i = 0; i < Arguments.Count; ++i)
-            {
-                object? value;
-
-                if (!TypeUtilities.TryConvert(typeof(int), Arguments[i], CultureInfo.InvariantCulture, out value))
-                {
-                    return false;
-                }
-
-                intArgs[i] = (int)value!;
-            }
-            return true;
-        }
-
-        private static PropertyInfo? GetIndexer(TypeInfo? typeInfo)
-        {
-            PropertyInfo indexer;
-
-            for (; typeInfo != null; typeInfo = typeInfo.BaseType?.GetTypeInfo())
-            {
-                // Check for the default indexer name first to make this faster.
-                // This will only be false when a class in VB has a custom indexer name.
-                if ((indexer = typeInfo.GetDeclaredProperty(CommonPropertyNames.IndexerName)!) != null)
-                {
-                    return indexer;
-                }
-
-                foreach (var property in typeInfo.DeclaredProperties)
-                {
-                    if (property.GetIndexParameters().Any())
-                    {
-                        return property;
-                    }
-                }
-            }
-
-            return null;
-        }
-
-        private static bool ValidBounds(int[] indices, Array array)
-        {
-            if (indices.Length == array.Rank)
-            {
-                for (var i = 0; i < indices.Length; ++i)
-                {
-                    if (indices[i] >= array.GetLength(i))
-                    {
-                        return false;
-                    }
-                }
-
-                return true;
-            }
-            else
-            {
-                return false;
-            }
-        }
-
-        protected override bool ShouldUpdate(object? sender, PropertyChangedEventArgs e)
-        {
-            if (sender is null || e.PropertyName is null)
-                return false;
-            var typeInfo = sender.GetType().GetTypeInfo();
-            return typeInfo.GetDeclaredProperty(e.PropertyName)?.GetIndexParameters().Any() ?? false;
-        }
-
-        protected override int? TryGetFirstArgumentAsInt()
-        {
-            if (TypeUtilities.TryConvert(typeof(int), Arguments[0], CultureInfo.InvariantCulture, out var value))
-            {
-                return (int?)value;
-            }
-            return null;
-        }
-    }
-}
diff --git a/src/Markup/Avalonia.Markup/Properties/AssemblyInfo.cs b/src/Markup/Avalonia.Markup/Properties/AssemblyInfo.cs
index 36ca2784d..afde09601 100644
--- a/src/Markup/Avalonia.Markup/Properties/AssemblyInfo.cs
+++ b/src/Markup/Avalonia.Markup/Properties/AssemblyInfo.cs
@@ -1,5 +1,8 @@
+using System.Runtime.CompilerServices;
+using Avalonia.Data;
 using Avalonia.Metadata;
 
 [assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia.Data")]
 [assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia.Markup.Data")]
 
+[assembly: TypeForwardedTo(typeof(CultureInfoIetfLanguageTagConverter))]
diff --git a/tests/Avalonia.Base.UnitTests/Animation/StyleAnimationTests.cs b/tests/Avalonia.Base.UnitTests/Animation/StyleAnimationTests.cs
new file mode 100644
index 000000000..e13b23a96
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/Animation/StyleAnimationTests.cs
@@ -0,0 +1,124 @@
+using System;
+using Avalonia.Animation;
+using Avalonia.Controls;
+using Avalonia.Data;
+using Avalonia.Styling;
+using Avalonia.UnitTests;
+using Xunit;
+
+namespace Avalonia.Base.UnitTests.Animation;
+using Animation = global::Avalonia.Animation.Animation;
+
+public class StyleAnimationTests
+{
+    [Fact]
+    public void Application_ControlTheme_Applies_Animation()
+    {
+        using var app = new AnimationTestApplication
+        {
+            Resources =
+            {
+                { typeof(Button), CreateControlTheme<Button>(CreateOpacityAnimation()) },
+            },
+        };
+
+        var target = new Button();
+        var root = CreateRoot(target, app);
+
+        app.Clock.Pulse(TimeSpan.Zero);
+        Assert.Equal(1, target.Opacity);
+        
+        app.Clock.Pulse(TimeSpan.FromSeconds(0.5));
+        Assert.Equal(0.5, target.Opacity);
+
+        app.Clock.Pulse(TimeSpan.FromSeconds(1));
+        Assert.Equal(0, target.Opacity);
+    }
+
+    [Fact]
+    public void Application_ControlTheme_Applies_Animation_With_Bound_KeyFrame_Values()
+    {
+        var fromBinding = new Binding("From");
+        var toBinding = new Binding("To");
+
+        using var app = new AnimationTestApplication
+        {
+            Resources =
+            {
+                { typeof(Button), CreateControlTheme<Button>(CreateOpacityAnimation(fromBinding, toBinding)) },
+            },
+        };
+
+        var target = new Button { DataContext = new KeyFrameValues(1.0, 0.0) };
+        var root = CreateRoot(target, app);
+
+        app.Clock.Pulse(TimeSpan.Zero);
+        Assert.Equal(1, target.Opacity);
+
+        app.Clock.Pulse(TimeSpan.FromSeconds(0.5));
+        Assert.Equal(0.5, target.Opacity);
+
+        app.Clock.Pulse(TimeSpan.FromSeconds(1));
+        Assert.Equal(0, target.Opacity);
+    }
+
+    private static ControlTheme CreateControlTheme<T>(Animation animation)
+    {
+        return new ControlTheme(typeof(T))
+        {
+            Animations = { animation }
+        };
+    }
+
+    private static object CreateRoot(Button child, Application app)
+    {
+        var root = new TestRoot{ StylingParent = app };
+        root.Child = child;
+        root.LayoutManager.ExecuteInitialLayoutPass();
+        return root;
+    }
+
+    private static Animation CreateOpacityAnimation()
+    {
+        return CreateOpacityAnimation(1.0, 0.0);
+    }
+
+    private static Animation CreateOpacityAnimation(object from, object to)
+    {
+        return new Animation
+        {
+            Duration = TimeSpan.FromSeconds(1),
+            FillMode = FillMode.Both,
+            Children =
+            {
+                new KeyFrame
+                {
+                    KeyTime = TimeSpan.FromSeconds(0),
+                    Setters = { new Setter(Button.OpacityProperty, from) }
+                },
+                new KeyFrame
+                {
+                    KeyTime = TimeSpan.FromSeconds(1),
+                    Setters = {new Setter(Button.OpacityProperty, to) }
+                },
+            }
+        };
+    }
+
+    private class AnimationTestApplication : Application, IDisposable
+    {
+        private readonly IDisposable _lifetime;
+
+        public AnimationTestApplication()
+        {
+            var services = new TestServices(globalClock: Clock);
+            _lifetime = UnitTestApplication.Start(services);
+        }
+
+        public MockGlobalClock Clock { get; } = new MockGlobalClock();
+
+        public void Dispose() => _lifetime.Dispose();
+    }
+
+    private record KeyFrameValues(double From, double To);
+}
diff --git a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Binding.cs b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Binding.cs
index e4080dd0a..71ce8eec5 100644
--- a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Binding.cs
+++ b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Binding.cs
@@ -462,7 +462,7 @@ namespace Avalonia.Base.UnitTests
             var target = new Class1();
             var source = new Subject<object>();
 
-            target.Bind(Class1.QuxProperty, new TestOneTimeBinding(source));
+            target.Bind(Class1.QuxProperty, source);
 
             source.OnNext(AvaloniaProperty.UnsetValue);
             Assert.Equal(5.6, target.GetValue(Class1.QuxProperty));
@@ -477,7 +477,7 @@ namespace Avalonia.Base.UnitTests
             var target = new Class1();
             var source = new Subject<object>();
 
-            target.Bind(Class1.QuxProperty, new TestOneTimeBinding(source));
+            target.Bind(Class1.QuxProperty, source);
 
             source.OnNext(new BindingNotification(new Exception(), BindingErrorType.Error));
             Assert.Equal(5.6, target.GetValue(Class1.QuxProperty));
@@ -853,103 +853,6 @@ namespace Avalonia.Base.UnitTests
             Assert.Equal("bar", target.GetValue(Class1.FooProperty));
         }
 
-        [Fact]
-        public void Bind_Logs_Binding_Error()
-        {
-            var target = new Class1();
-            var source = new Subject<BindingValue<double>>();
-            var called = false;
-            var expectedMessageTemplate = "Error in binding to {Target}.{Property}: {Message}";
-
-            LogCallback checkLogMessage = (level, area, src, mt, pv) =>
-            {
-                if (level == LogEventLevel.Warning &&
-                    area == LogArea.Binding &&
-                    mt == expectedMessageTemplate)
-                {
-                    called = true;
-                }
-            };
-
-            using (TestLogSink.Start(checkLogMessage))
-            {
-                target.Bind(Class1.QuxProperty, source);
-                source.OnNext(6.7);
-                source.OnNext(BindingValue<double>.BindingError(new InvalidOperationException("Foo")));
-
-                Assert.Equal(5.6, target.GetValue(Class1.QuxProperty));
-                Assert.True(called);
-            }
-        }
-
-        [Fact]
-        public void Untyped_LocalValue_Binding_Logs_Invalid_Value_Type()
-        {
-            var target = new Class1();
-            var source = new Subject<object?>();
-            var called = false;
-            var expectedMessageTemplate = "Error in binding to {Target}.{Property}: {Message}";
-            var message = "Unable to convert object 'foo' of type 'System.String' to type 'System.Double'.";
-
-            LogCallback checkLogMessage = (level, area, src, mt, pv) =>
-            {
-                if (level == LogEventLevel.Warning &&
-                    area == LogArea.Binding &&
-                    mt == expectedMessageTemplate &&
-                    src == target &&
-                    pv[0].GetType() == typeof(Class1) &&
-                    (AvaloniaProperty)pv[1] == Class1.QuxProperty &&
-                    (string)pv[2] == message)
-                {
-                    called = true;
-                }
-            };
-
-            using (TestLogSink.Start(checkLogMessage))
-            {
-                target.Bind(Class1.QuxProperty, source);
-                source.OnNext(1.2);
-                source.OnNext("foo");
-
-                Assert.Equal(5.6, target.GetValue(Class1.QuxProperty));
-                Assert.True(called);
-            }
-        }
-
-        [Fact]
-        public void Untyped_Style_Binding_Logs_Invalid_Value_Type()
-        {
-            var target = new Class1();
-            var source = new Subject<object?>();
-            var called = false;
-            var expectedMessageTemplate = "Error in binding to {Target}.{Property}: {Message}";
-            var expectedMessage = "Unable to convert object 'foo' of type 'System.String' to type 'System.Double'.";
-
-            LogCallback checkLogMessage = (level, area, src, mt, pv) =>
-            {
-                if (level == LogEventLevel.Warning &&
-                    area == LogArea.Binding &&
-                    mt == expectedMessageTemplate &&
-                    src == target &&
-                    pv[0].GetType() == typeof(Class1) &&
-                    (AvaloniaProperty)pv[1] == Class1.QuxProperty &&
-                    (string)pv[2] == expectedMessage)
-                {
-                    called = true;
-                }
-            };
-
-            using (TestLogSink.Start(checkLogMessage))
-            {
-                target.Bind(Class1.QuxProperty, source, BindingPriority.Style);
-                source.OnNext(1.2);
-                source.OnNext("foo");
-
-                Assert.Equal(5.6, target.GetValue(Class1.QuxProperty));
-                Assert.True(called);
-            }
-        }
-
         [Theory]
         [InlineData(BindingPriority.LocalValue)]
         [InlineData(BindingPriority.Style)]
diff --git a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Direct.cs b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Direct.cs
index ad8c2751c..a7f00fe94 100644
--- a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Direct.cs
+++ b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Direct.cs
@@ -489,37 +489,6 @@ namespace Avalonia.Base.UnitTests
             Assert.Equal("fallback", target.GetValue(Class1.FooProperty));
         }
 
-        [Fact]
-        public void Binding_To_Direct_Property_Logs_BindingError()
-        {
-            var target = new Class1();
-            var source = new Subject<BindingValue<string>>();
-            var called = false;
-
-            LogCallback checkLogMessage = (level, area, src, mt, pv) =>
-            {
-                if (level == LogEventLevel.Warning &&
-                    area == LogArea.Binding &&
-                    mt == "Error in binding to {Target}.{Property}: {Message}" &&
-                    pv.Length == 3 &&
-                    pv[0] is Class1 &&
-                    object.ReferenceEquals(pv[1], Class1.FooProperty) &&
-                    (string)pv[2] == "Binding Error Message")
-                {
-                    called = true;
-                }
-            };
-
-            using (TestLogSink.Start(checkLogMessage))
-            {
-                target.Bind(Class1.FooProperty, source);
-                source.OnNext("baz");
-                source.OnNext(BindingValue<string>.BindingError(new InvalidOperationException("Binding Error Message")));
-            }
-
-            Assert.True(called);
-        }
-
         [Fact]
         public void Bind_Executes_On_UIThread()
         {
diff --git a/tests/Avalonia.Base.UnitTests/AvaloniaPropertyTests.cs b/tests/Avalonia.Base.UnitTests/AvaloniaPropertyTests.cs
index d974351b1..d23151ca1 100644
--- a/tests/Avalonia.Base.UnitTests/AvaloniaPropertyTests.cs
+++ b/tests/Avalonia.Base.UnitTests/AvaloniaPropertyTests.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using Avalonia.Data;
+using Avalonia.Data.Core;
 using Avalonia.PropertyStore;
 using Xunit;
 
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.AttachedProperty.cs b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.AttachedProperty.cs
new file mode 100644
index 000000000..0271bb161
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.AttachedProperty.cs
@@ -0,0 +1,132 @@
+using System;
+using Avalonia.Data.Core;
+using Avalonia.Diagnostics;
+using Xunit;
+
+#nullable enable
+
+namespace Avalonia.Base.UnitTests.Data.Core;
+
+public partial class BindingExpressionTests
+{
+    [Fact]
+    public void Should_Get_Attached_Property_Value()
+    {
+        var data = new SourceControl { [AttachedProperties.AttachedStringProperty] = "foo" };
+        var target = CreateTargetWithSource(
+            data,
+            o => o[AttachedProperties.AttachedStringProperty],
+            targetProperty: TargetClass.StringProperty);
+
+        Assert.Equal("foo", target.String);
+    }
+
+    [Fact]
+    public void Should_Get_Chained_Attached_Property_Value()
+    {
+        var data = new SourceControl 
+        { 
+            Next = new() { [AttachedProperties.AttachedStringProperty] = "foo" }
+        };
+
+        var target = CreateTargetWithSource(
+            data,
+            o => o.Next![AttachedProperties.AttachedStringProperty],
+            targetProperty: TargetClass.StringProperty);
+
+        Assert.Equal("foo", target.String);
+    }
+
+    [Fact]
+    public void Should_Track_Simple_Attached_Value()
+    {
+        var data = new SourceControl { [AttachedProperties.AttachedStringProperty] = "foo" };
+        var target = CreateTargetWithSource(
+            data,
+            o => o[AttachedProperties.AttachedStringProperty],
+            targetProperty: TargetClass.StringProperty);
+
+        Assert.Equal("foo", target.String);
+
+        data.SetValue(AttachedProperties.AttachedStringProperty, "bar");
+
+        Assert.Equal("bar", target.String);
+    }
+
+    [Fact]
+    public void Should_Track_Chained_Attached_Value()
+    {
+        var data = new SourceControl
+        {
+            Next = new() { [AttachedProperties.AttachedStringProperty] = "foo" }
+        };
+
+        var target = CreateTargetWithSource(
+            data,
+            o => o.Next![AttachedProperties.AttachedStringProperty],
+            targetProperty: TargetClass.StringProperty);
+
+        Assert.Equal("foo", target.String);
+
+        data.Next!.SetValue(AttachedProperties.AttachedStringProperty, "bar");
+
+        Assert.Equal("bar", target.String);
+    }
+
+    [Fact]
+    public void Should_Unsubscribe_From_AttachedProperty_Source()
+    {
+        var data = new SourceControl { [AttachedProperties.AttachedStringProperty] = "foo" };
+        var (target, expression) = CreateTargetAndExpression<SourceControl, object?>(
+            o => o[AttachedProperties.AttachedStringProperty],
+            source: data,
+            targetProperty: TargetClass.StringProperty);
+
+        Assert.NotNull(((IAvaloniaObjectDebug)data).GetPropertyChangedSubscribers());
+        
+        expression.Dispose();
+
+        Assert.Null(((IAvaloniaObjectDebug)data).GetPropertyChangedSubscribers());
+    }
+
+    [Fact]
+    public void Should_Unsubscribe_From_Chained_Source()
+    {
+        var data = new SourceControl
+        {
+            Next = new() { [AttachedProperties.AttachedStringProperty] = "foo" }
+        };
+
+        var (target, expression) = CreateTargetAndExpression<SourceControl, object?>(
+            o => o.Next![AttachedProperties.AttachedStringProperty],
+            source: data,
+            targetProperty: TargetClass.StringProperty);
+
+        Assert.NotNull(((IAvaloniaObjectDebug)data.Next).GetPropertyChangedSubscribers());
+
+        expression.Dispose();
+
+        Assert.Null(((IAvaloniaObjectDebug)data.Next).GetPropertyChangedSubscribers());
+    }
+
+    [Fact]
+    public void Should_Not_Keep_Attached_Property_Source_Alive()
+    {
+        Func<(TargetClass, WeakReference<SourceControl>)> run = () =>
+        {
+            var source = new SourceControl();
+            var target = CreateTargetWithSource(
+                source,
+                o => o.Next![AttachedProperties.AttachedStringProperty],
+                targetProperty: TargetClass.StringProperty);
+            return (target, new WeakReference<SourceControl>(source));
+        };
+
+        var result = run();
+
+        GC.Collect();
+
+        Assert.False(result.Item2.TryGetTarget(out _));
+        GC.KeepAlive(result.Item1);
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.AvaloniaProperty.cs b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.AvaloniaProperty.cs
new file mode 100644
index 000000000..af39e4287
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.AvaloniaProperty.cs
@@ -0,0 +1,79 @@
+using System;
+using System.Collections.Generic;
+using Avalonia.Diagnostics;
+using Xunit;
+
+#nullable enable
+
+namespace Avalonia.Base.UnitTests.Data.Core;
+
+public partial class BindingExpressionTests
+{
+    [Fact]
+    public void Should_Get_Simple_AvaloniaProperty_Value()
+    {
+        var data = new SourceControl { StringValue = "foo" };
+        var target = CreateTargetWithSource(data, o => o.StringValue);
+
+        Assert.Equal("foo", target.String);
+    }
+
+    [Fact]
+    public void Should_Get_Simple_ClrProperty_Value()
+    {
+        var data = new SourceControl { ClrProperty = "foo" };
+        var target = CreateTargetWithSource(data, o => o.ClrProperty);
+
+        Assert.Equal("foo", target.String);
+    }
+
+    [Fact]
+    public void Should_Track_Simple_AvaloniaProperty_Value()
+    {
+        var data = new SourceControl { StringValue = "foo" };
+        var target = CreateTargetWithSource(data, o => o.StringValue);
+        var result = new List<object>();
+
+        Assert.Equal("foo", target.String);
+
+        data.StringValue = "bar";
+
+        Assert.Equal("bar", target.String);
+    }
+
+    [Fact]
+    public void Should_Unsubscribe_From_AvaloniaProperty_Source()
+    {
+        var data = new SourceControl { StringValue = "foo" };
+        var (target, expression) = CreateTargetAndExpression<SourceControl, object?>(
+            o => o.StringValue,
+            source: data,
+            targetProperty: TargetClass.StringProperty);
+
+        Assert.NotNull(((IAvaloniaObjectDebug)data).GetPropertyChangedSubscribers());
+
+        expression.Dispose();
+
+        Assert.Null(((IAvaloniaObjectDebug)data).GetPropertyChangedSubscribers());
+    }
+
+    [Fact]
+    public void Should_Not_Keep_AvaloniaProperty_Source_Alive()
+    {
+        Func<(TargetClass, WeakReference<SourceControl>)> run = () =>
+        {
+            var source = new SourceControl();
+            var target = CreateTargetWithSource(
+                source,
+                o => o.StringValue,
+                targetProperty: TargetClass.StringProperty);
+            return (target, new WeakReference<SourceControl>(source));
+        };
+
+        var result = run();
+
+        GC.Collect();
+
+        Assert.False(result.Item2.TryGetTarget(out _));
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.DataValidation.cs b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.DataValidation.cs
new file mode 100644
index 000000000..bedf24bd6
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.DataValidation.cs
@@ -0,0 +1,361 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using Avalonia.Data;
+using Avalonia.UnitTests;
+using Xunit;
+
+#nullable enable
+
+namespace Avalonia.Base.UnitTests.Data.Core;
+
+public partial class BindingExpressionTests
+{
+    [Fact]
+    public void Root_Null_Should_Update_Data_Validation()
+    {
+        var target = CreateTargetWithSource<ViewModel?, string?>(
+            null,
+            o => o!.StringValue,
+            enableDataValidation: true);
+
+        AssertBindingError(
+            target,
+            TargetClass.StringProperty,
+            new BindingChainException("Binding Source is null.", "StringValue", "(source)"),
+            BindingErrorType.Error);
+    }
+
+    [Fact]
+    public void Null_Value_In_Path_Should_Update_Data_Validation()
+    {
+        var data = new { Foo = default(ViewModel) };
+        var target = CreateTargetWithSource(
+            data,
+            o => o.Foo!.StringValue!.Length, 
+            enableDataValidation: true);
+
+        AssertBindingError(
+            target,
+            TargetClass.IntProperty,
+            new BindingChainException("Value is null.", "Foo.StringValue.Length", "Foo"),
+            BindingErrorType.Error);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Invalid_Double_String_Should_Update_Data_Validation()
+    {
+        var data = new ViewModel { StringValue = "foo" };
+        var target = CreateTargetWithSource(
+            data, 
+            o => o.StringValue, 
+            enableDataValidation: true,
+            targetProperty: TargetClass.DoubleProperty);
+
+        AssertBindingError(
+            target,
+            TargetClass.DoubleProperty,
+            new InvalidCastException("Could not convert 'foo' (System.String) to 'System.Double'."),
+            BindingErrorType.Error);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Invalid_Double_String_Should_Revert_To_FallbackValue()
+    {
+        var data = new ViewModel { StringValue = "foo" };
+        var target = CreateTargetWithSource(
+            data,
+            o => o.StringValue,
+            enableDataValidation: true,
+            fallbackValue: 42.0,
+            targetProperty: TargetClass.DoubleProperty);
+
+        Assert.Equal(42.0, target.Double);
+        AssertBindingError(
+            target,
+            TargetClass.DoubleProperty,
+            new InvalidCastException("Could not convert 'foo' (System.String) to 'System.Double'."),
+            BindingErrorType.Error);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Setter_Exception_Does_Not_Cause_DataValidationError_When_Data_Validation_Not_Enabled()
+    {
+        var data = new ExceptionViewModel { MustBePositive = 5 };
+
+        var target = CreateTargetWithSource(
+            data,
+            o => o.MustBePositive,
+            enableDataValidation: false,
+            mode: BindingMode.TwoWay);
+
+        target.Int = -5;
+
+        // TODO: Should this be 5?
+        Assert.Equal(-5, target.Int);
+
+        Assert.Equal(5, data.MustBePositive);
+        AssertNoError(target, TargetClass.IntProperty);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Setter_Exception_Updates_Data_Validation()
+    {
+        var data = new ExceptionViewModel { MustBePositive = 5 };
+
+        var target = CreateTargetWithSource(
+            data,
+            o => o.MustBePositive,
+            enableDataValidation: true,
+            mode: BindingMode.TwoWay);
+
+        target.Int = -5;
+
+        // TODO: Should this be 5?
+        Assert.Equal(-5, target.Int);
+
+        Assert.Equal(5, data.MustBePositive);
+        AssertBindingError(
+            target,
+            TargetClass.IntProperty,
+            new ArgumentOutOfRangeException("value"),
+            BindingErrorType.DataValidationError);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Indei_Validation_Does_Not_Subscribe_When_DataValidation_Not_Enabled()
+    {
+        var data = new IndeiViewModel { MustBePositive = 5 };
+        var target = CreateTargetWithSource(
+            data,
+            o => o.MustBePositive,
+            enableDataValidation: false,
+            mode: BindingMode.TwoWay);
+
+        Assert.Equal(0, data.ErrorsChangedSubscriptionCount);
+    }
+
+    [Fact]
+    public void Indei_Validation_Subscribes_And_Unsubscribes()
+    {
+        var data = new IndeiViewModel { MustBePositive = 5 };
+        var (target, expression) = CreateTargetAndExpression<IndeiViewModel, int>(
+            o => o.MustBePositive,
+            enableDataValidation: true,
+            mode: BindingMode.TwoWay,
+            source: data);
+
+        Assert.Equal(1, data.ErrorsChangedSubscriptionCount);
+
+        expression.Dispose();
+
+        Assert.Equal(0, data.ErrorsChangedSubscriptionCount);
+    }
+
+    [Fact]
+    public void Conversion_Errors_Update_Data_Validation_When_Writing_To_Source()
+    {
+        var data = new ViewModel { DoubleValue = 5.6 };
+        var target = CreateTargetWithSource(
+            data,
+            o => o.DoubleValue,
+            enableDataValidation: true,
+            mode: BindingMode.TwoWay,
+            targetProperty: TargetClass.TagProperty);
+
+        // Can write a double value.
+        target.Tag = 1.2;
+
+        Assert.Equal(1.2, data.DoubleValue);
+        AssertNoError(target, TargetClass.StringProperty);
+
+        // Can write a string value and it gets converted to double.
+        target.Tag = "3.4";
+
+        Assert.Equal(3.4, data.DoubleValue);
+        AssertNoError(target, TargetClass.StringProperty);
+
+        // An invalid string value should result in an error. Not sure why this is considered
+        // a data validation error rather than a binding error, but preserving semantics.
+        target.Tag = "bar";
+
+        Assert.Equal(3.4, data.DoubleValue);
+        AssertBindingError(
+            target,
+            TargetClass.TagProperty,
+            new InvalidCastException("Could not convert 'bar' (System.String) to System.Double."),
+            BindingErrorType.DataValidationError);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Indei_Validation_Updates_Data_Validation_When_Writing_To_Source()
+    {
+        var data = new IndeiViewModel();
+        var target = CreateTargetWithSource(
+            data,
+            o => o.MustBePositive,
+            enableDataValidation: true,
+            mode: BindingMode.TwoWay);
+
+        Assert.Equal(0, target.Int);
+        Assert.Equal(0, data.MustBePositive);
+        AssertNoError(target, TargetClass.IntProperty);
+
+        target.Int = 5;
+
+        Assert.Equal(5, target.Int);
+        Assert.Equal(5, data.MustBePositive);
+        AssertNoError(target, TargetClass.IntProperty);
+
+        target.Int = -5;
+
+        Assert.Equal(-5, target.Int);
+        Assert.Equal(-5, data.MustBePositive);
+        AssertBindingError(target, TargetClass.IntProperty, new DataValidationException("Must be positive"), BindingErrorType.DataValidationError);
+
+        target.Int = 5;
+
+        Assert.Equal(5, target.Int);
+        Assert.Equal(5, data.MustBePositive);
+        AssertNoError(target, TargetClass.IntProperty);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Does_Not_Subscribe_To_Indei_Of_Intermediate_Object_In_Chain()
+    {
+        var data = new IndeiContainerViewModel { Inner = new() };
+
+        var target = CreateTargetWithSource(
+            data,
+            o => o.Inner!.MustBePositive,
+            enableDataValidation: true,
+            mode: BindingMode.TwoWay);
+
+        // We may want to change this but I've never seen an example of data validation on an
+        // intermediate object in a chain so for the moment I'm not sure what the result of 
+        // validating such a thing should look like.
+        Assert.Equal(0, data.ErrorsChangedSubscriptionCount);
+        Assert.Equal(1, data.Inner.ErrorsChangedSubscriptionCount);
+    }
+
+    [Fact]
+    public void Updates_Data_Validation_For_Null_Value_In_Property_Chain()
+    {
+        var data = new IndeiContainerViewModel();
+        var target = CreateTargetWithSource(
+            data,
+            o => o.Inner!.MustBePositive,
+            enableDataValidation: true,
+            mode: BindingMode.TwoWay);
+
+        AssertBindingError(
+            target, 
+            TargetClass.IntProperty,
+            new BindingChainException("Value is null.", "Inner.MustBePositive", "Inner"),
+            BindingErrorType.Error);
+
+        GC.KeepAlive(data);
+    }
+
+    public class ExceptionViewModel : NotifyingBase
+    {
+        private int _mustBePositive;
+
+        public int MustBePositive
+        {
+            get { return _mustBePositive; }
+            set
+            {
+                if (value <= 0)
+                {
+                    throw new ArgumentOutOfRangeException(nameof(value));
+                }
+
+                _mustBePositive = value;
+                RaisePropertyChanged();
+            }
+        }
+    }
+
+    private class IndeiViewModel : IndeiBase
+    {
+        private int _mustBePositive;
+        private Dictionary<string, IList<string>> _errors = new Dictionary<string, IList<string>>();
+
+        public int MustBePositive
+        {
+            get { return _mustBePositive; }
+            set
+            {
+                _mustBePositive = value;
+                RaisePropertyChanged();
+
+                if (value >= 0)
+                {
+                    _errors.Remove(nameof(MustBePositive));
+                    RaiseErrorsChanged(nameof(MustBePositive));
+                }
+                else
+                {
+                    _errors[nameof(MustBePositive)] = new[] { "Must be positive" };
+                    RaiseErrorsChanged(nameof(MustBePositive));
+                }
+            }
+        }
+
+        public override bool HasErrors => _mustBePositive >= 0;
+
+        public override IEnumerable? GetErrors(string propertyName)
+        {
+            IList<string>? result;
+            _errors.TryGetValue(propertyName, out result);
+            return result;
+        }
+    }
+
+    private class IndeiContainerViewModel : IndeiBase
+    {
+        private IndeiViewModel? _inner;
+
+        public IndeiViewModel? Inner
+        {
+            get { return _inner; }
+            set { _inner = value; RaisePropertyChanged(); }
+        }
+
+        public override bool HasErrors => false;
+        public override IEnumerable? GetErrors(string propertyName) => null;
+    }
+
+    private static void AssertNoError(TargetClass target, AvaloniaProperty property)
+    {
+        Assert.False(target.BindingNotifications.TryGetValue(property, out var notification));
+    }
+
+    private static void AssertBindingError(
+        TargetClass target,
+        AvaloniaProperty property,
+        Exception expectedException,
+        BindingErrorType errorType)
+    {
+        Assert.True(target.BindingNotifications.TryGetValue(property, out var notification));
+        Assert.Equal(errorType, notification.ErrorType);
+        Assert.NotNull(notification.Error);
+        Assert.IsType(expectedException.GetType(), notification.Error);
+        Assert.Equal(expectedException.Message, notification.Error.Message);
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.GetValue.cs b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.GetValue.cs
new file mode 100644
index 000000000..8d7f56175
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.GetValue.cs
@@ -0,0 +1,144 @@
+using System;
+using Avalonia.Data;
+using Xunit;
+
+#nullable enable
+
+namespace Avalonia.Base.UnitTests.Data.Core;
+
+public abstract partial class BindingExpressionTests
+{
+    [Fact]
+    public void Should_Get_Source_Value()
+    {
+        var data = "foo";
+        var target = CreateTargetWithSource(data, o => o);
+
+        Assert.Equal("foo", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Convert_String_To_Double()
+    {
+        var data = new ViewModel { StringValue = $"{5.6}" };
+        var target = CreateTargetWithSource(
+            data, 
+            o => o.StringValue,
+            targetProperty: TargetClass.DoubleProperty);
+
+        Assert.Equal(5.6, target.Double);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Convert_Double_To_String()
+    {
+        var data = new ViewModel { DoubleValue = 5.6 };
+        var target = CreateTargetWithSource(
+            data,
+            o => o.DoubleValue,
+            targetProperty: TargetClass.StringProperty);
+
+        Assert.Equal($"{5.6}", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Use_FallbackValue_For_NonConvertible_Target_Value()
+    {
+        var data = new ViewModel { StringValue = "foo" };
+        var target = CreateTargetWithSource(
+            data,
+            o => o.StringValue,
+            fallbackValue: 42,
+            targetProperty: TargetClass.IntProperty);
+
+        Assert.Equal(42, target.Int);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Pass_ConverterParameter_To_Converter()
+    {
+        var data = new ViewModel { DoubleValue = 5.6 };
+        var converter = new PrefixConverter();
+        var target = CreateTargetWithSource(
+            data,
+            o => o.DoubleValue,         
+            converter: converter,
+            converterParameter: "foo",
+            targetProperty: TargetClass.StringProperty);
+
+        Assert.Equal("foo5.6", target.String);
+    }
+
+    [Fact]
+    public void TargetNullValue_Should_Be_Used_When_Source_String_Is_Null()
+    {
+        var data = new ViewModel { StringValue = "foo" };
+        var target = CreateTargetWithSource(
+            data, 
+            o => o.StringValue,
+            targetNullValue: "bar");
+
+        Assert.Equal("foo", target.String);
+
+        data.StringValue = null;
+        Assert.Equal("bar", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Can_Use_UpdateTarget_To_Update_From_Non_INPC_Data()
+    {
+        var data = new PodViewModel { StringValue = "foo" };
+        var (target, expression) = CreateTargetAndExpression<PodViewModel, string?>(
+            o => o.StringValue,
+            source: data);
+
+        Assert.Equal("foo", target.String);
+
+        data.StringValue = "bar";
+        Assert.Equal("foo", target.String);
+
+        expression.UpdateTarget();
+        Assert.Equal("bar", target.String);
+    }
+
+    [Fact]
+    public void Should_Use_Converter_For_RelativeSource_Self_Binding_With_No_Path()
+    {
+        var converter = new PrefixConverter();
+        var target = CreateTarget<TargetClass, TargetClass>(
+            o => o,
+            converter: converter,
+            converterParameter: "foo",
+            relativeSource: new RelativeSource(RelativeSourceMode.Self),
+            targetProperty: TargetClass.StringProperty);
+
+        Assert.Equal("fooTargetClass", target.String);
+    }
+
+    [Fact]
+    public void Should_Not_Pass_UnsetValue_To_Converter_Until_First_Value_Produced()
+    {
+        var data = new ViewModel { StringValue = "Bar" };
+        var converter = new PrefixConverter();
+        var target = CreateTarget<ViewModel, string?>(
+            o => o.StringValue,
+            converter: converter,
+            converterParameter: "foo");
+
+        Assert.Null(target.String);
+
+        target.DataContext = data;
+
+        Assert.Equal("fooBar", target.String);
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Indexer.cs b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Indexer.cs
new file mode 100644
index 000000000..ef64e546b
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Indexer.cs
@@ -0,0 +1,299 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using Avalonia.Collections;
+using Avalonia.Data;
+using Avalonia.Data.Core;
+using Avalonia.Threading;
+using Avalonia.UnitTests;
+using Xunit;
+
+#nullable enable
+
+namespace Avalonia.Base.UnitTests.Data.Core;
+
+public partial class BindingExpressionTests
+{
+    [Fact]
+    public void Should_Get_Array_Value()
+    {
+        var data = new { Foo = new[] { "foo", "bar" } };
+        var target = CreateTargetWithSource(data, o => o.Foo[1]);
+
+        Assert.Equal("bar", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Get_MultiDimensional_Array_Value()
+    {
+        var data = new { Foo = new[,] { { "foo", "bar" }, { "baz", "qux" } } };
+        var target = CreateTargetWithSource(data, o => o.Foo[1, 1]);
+
+        Assert.Equal("qux", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Get_Value_For_String_Indexer()
+    {
+        var data = new { Foo = new Dictionary<string, string> { { "foo", "bar" }, { "baz", "qux" } } };
+        var target = CreateTargetWithSource(data, o => o.Foo["foo"]);
+
+        Assert.Equal("bar", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Get_Value_For_Non_String_Indexer()
+    {
+        var data = new { Foo = new Dictionary<double, string> { { 1.0, "bar" }, { 2.0, "qux" } } };
+        var target = CreateTargetWithSource(data, o => o.Foo[1.0]);
+
+        Assert.Equal("bar", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Array_Out_Of_Bounds_Should_Return_UnsetValue()
+    {
+        var data = new { Foo = new[] { "foo", "bar" } };
+        var target = CreateTargetWithSource(data, o => o.Foo[2]);
+
+        Assert.False(target.IsSet(TargetClass.StringProperty));
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void List_Out_Of_Bounds_Should_Return_UnsetValue()
+    {
+        var data = new { Foo = new List<string> { "foo", "bar" } };
+        var target = CreateTargetWithSource(data, o => o.Foo[2]);
+
+        Assert.False(target.IsSet(TargetClass.StringProperty));
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Get_List_Value()
+    {
+        var data = new { Foo = new List<string> { "foo", "bar" } };
+        var target = CreateTargetWithSource(data, o => o.Foo[1]);
+
+        Assert.Equal("bar", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Track_INCC_Add()
+    {
+        var data = new { Foo = new AvaloniaList<string> { "foo", "bar" } };
+        var target = CreateTargetWithSource(data, o => o.Foo[2]);
+
+        Assert.False(target.IsSet(TargetClass.StringProperty));
+
+        data.Foo.Add("baz");
+
+        Assert.Equal("baz", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Track_INCC_Remove()
+    {
+        var data = new { Foo = new AvaloniaList<string> { "foo", "bar" } };
+        var target = CreateTargetWithSource(data, o => o.Foo[0]);
+
+        Assert.Equal("foo", target.String);
+
+        data.Foo.RemoveAt(0);
+
+        Assert.Equal("bar", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Track_INCC_Replace()
+    {
+        var data = new { Foo = new AvaloniaList<string> { "foo", "bar" } };
+        var target = CreateTargetWithSource(data, o => o.Foo[1]);
+
+        Assert.Equal("bar", target.String);
+
+        data.Foo[1] = "baz";
+
+        Assert.Equal("baz", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Track_INCC_Move()
+    {
+        // Using ObservableCollection here because AvaloniaList does not yet have a Move
+        // method, but even if it did we need to test with ObservableCollection as well
+        // as AvaloniaList as it implements PropertyChanged as an explicit interface event.
+        var data = new { Foo = new ObservableCollection<string> { "foo", "bar" } };
+        var target = CreateTargetWithSource(data, o => o.Foo[1]);
+
+        Assert.Equal("bar", target.String);
+
+        data.Foo.Move(0, 1);
+
+        Assert.Equal("foo", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Track_INCC_Reset()
+    {
+        var data = new { Foo = new AvaloniaList<string> { "foo", "bar" } };
+        var target = CreateTargetWithSource(data, o => o.Foo[1]);
+        var result = new List<object?>();
+
+        Assert.Equal("bar", target.String);
+
+        data.Foo.Clear();
+
+        Assert.Equal(null, target.String);
+    }
+
+    [Fact]
+    public void Should_Track_NonIntegerIndexer()
+    {
+        var data = new { Foo = new NonIntegerIndexer() };
+        data.Foo["foo"] = "bar";
+        data.Foo["baz"] = "qux";
+
+        var target = CreateTargetWithSource(data, o => o.Foo["foo"]);
+
+        Assert.Equal("bar", target.String);
+
+        data.Foo["foo"] = "bar2";
+
+        // Forces WeakEvent compact
+        Dispatcher.UIThread.RunJobs();
+
+        Assert.Equal("bar2", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_SetArrayIndex()
+    {
+        var data = new { Foo = new[] { "foo", "bar" } };
+        var target = CreateTargetWithSource(
+            data,
+            o => o.Foo[1],
+            mode: BindingMode.TwoWay);
+
+        target.String = "baz";
+
+        Assert.Equal("baz", data.Foo[1]);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Set_ExistingDictionaryEntry()
+    {
+        var data = new
+        {
+            Foo = new Dictionary<string, int>
+            {
+                {"foo", 1 }
+            }
+        };
+
+        var target = CreateTargetWithSource(
+            data, 
+            o => o.Foo["foo"],
+            mode: BindingMode.TwoWay);
+
+        target.Int = 4;
+
+        Assert.Equal(4, data.Foo["foo"]);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Add_NewDictionaryEntry()
+    {
+        var data = new
+        {
+            Foo = new Dictionary<string, int>
+            {
+                {"foo", 1 }
+            }
+        };
+
+        var target = CreateTargetWithSource(
+            data, 
+            o => o.Foo["bar"],
+            mode: BindingMode.TwoWay);
+
+        target.Int = 4;
+
+        Assert.Equal(4, data.Foo["bar"]);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Set_NonIntegerIndexer()
+    {
+        var data = new { Foo = new NonIntegerIndexer() };
+        data.Foo["foo"] = "bar";
+        data.Foo["baz"] = "qux";
+
+        var target = CreateTargetWithSource(
+            data, 
+            o => o.Foo["foo"],
+            mode: BindingMode.TwoWay);
+
+        target.String = "bar2";
+
+        Assert.Equal("bar2", data.Foo["foo"]);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Indexer_Only_Binding_Works()
+    {
+        var data = new[] { 1, 2, 3 };
+        var target = CreateTargetWithSource(data, o => o[1]);
+
+        Assert.Equal(data[1], target.Int);
+    }
+
+    private class NonIntegerIndexer : NotifyingBase
+    {
+        private readonly Dictionary<string, string> _storage = new Dictionary<string, string>();
+
+        public string this[string key]
+        {
+            get
+            {
+                return _storage[key];
+            }
+            set
+            {
+                _storage[key] = value;
+                RaisePropertyChanged(CommonPropertyNames.IndexerName);
+            }
+        }
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Mode.cs b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Mode.cs
new file mode 100644
index 000000000..3cbd5eae1
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Mode.cs
@@ -0,0 +1,70 @@
+using Avalonia.Data;
+using Xunit;
+
+#nullable enable
+
+namespace Avalonia.Base.UnitTests.Data.Core;
+
+public partial class BindingExpressionTests
+{
+    [Fact]
+    public void OneTime_Binding_Sets_Target_Only_Once()
+    {
+        var data = new ViewModel { StringValue = "foo" };
+        var target = CreateTargetWithSource(data, x => x.StringValue, mode: BindingMode.OneTime);
+
+        Assert.Equal("foo", target.String);
+
+        data.StringValue = "bar";
+        Assert.Equal("foo", target.String);
+    }
+
+    [Fact]
+    public void OneTime_Binding_Waits_For_DataContext()
+    {
+        var data = new ViewModel { StringValue = "foo" };
+        var target = CreateTarget<ViewModel, string?>(
+            x => x.StringValue,
+            mode: BindingMode.OneTime);
+
+        Assert.Null(target.String);
+    }
+
+    [Fact]
+    public void OneTime_Binding_Waits_For_DataContext_With_Matching_Property_Name()
+    {
+        var data1 = new { Baz = "baz" };
+        var data2 = new ViewModel { StringValue = "foo" };
+        var target = CreateTarget<ViewModel, string?>(
+            x => x.StringValue,
+            dataContext: data1,
+            mode: BindingMode.OneTime);
+
+        Assert.Null(target.String);
+
+        target.DataContext = data2;
+        Assert.Equal("foo", target.String);
+
+        data2.StringValue = "bar";
+        Assert.Equal("foo", target.String);
+    }
+
+    [Fact]
+    public void OneTime_Binding_Waits_For_DataContext_With_Matching_Property_Type()
+    {
+        var data1 = new { DoubleValue = new object() };
+        var data2 = new ViewModel { DoubleValue = 0.5 };
+        var target = CreateTarget<ViewModel, double>(
+            x => x.DoubleValue,
+            dataContext: data1,
+            mode: BindingMode.OneTime);
+
+        Assert.Equal(0, target.Double);
+
+        target.DataContext = data2;
+        Assert.Equal(0.5, target.Double);
+
+        data2.DoubleValue = 0.2;
+        Assert.Equal(0.5, target.Double);
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Negation.cs b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Negation.cs
new file mode 100644
index 000000000..468bb46aa
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Negation.cs
@@ -0,0 +1,107 @@
+using System;
+using Avalonia.Data;
+using Xunit;
+
+#nullable enable
+
+namespace Avalonia.Base.UnitTests.Data.Core
+{
+    public partial class BindingExpressionTests
+    {
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public void Should_Negate_Boolean_Value(bool value)
+        {
+            var data = new ViewModel { BoolValue = value };
+            var target = CreateTargetWithSource(data, o => !o.BoolValue);
+
+            //Assert.Equal(!value, target.Bool);
+
+            GC.KeepAlive(data);
+        }
+
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public void Should_Negate_Boolean_Value_In_Path(bool value)
+        {
+            var data = new ViewModel { Next = new() { BoolValue = value } };
+            var target = CreateTargetWithSource(data, o => !o.Next!.BoolValue);
+
+            Assert.Equal(!value, (bool)target.Bool);
+
+            GC.KeepAlive(data);
+        }
+
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public void Should_Double_Negate_Boolean_Value(bool value)
+        {
+            var data = new ViewModel { BoolValue = value };
+            var target = CreateTargetWithSource(data, o => !!o.BoolValue);
+
+            Assert.Equal(value, (bool)target.Bool);
+
+            GC.KeepAlive(data);
+        }
+
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public void Should_Double_Negate_Boolean_Value_In_Path(bool value)
+        {
+            var data = new ViewModel { Next = new() { BoolValue = value } };
+            var target = CreateTargetWithSource(data, o => !!o.Next!.BoolValue);
+
+            Assert.Equal(value, (bool)target.Bool);
+
+            GC.KeepAlive(data);
+        }
+
+        [Fact]
+        public void Can_Set_Negated_Value()
+        {
+            var data = new ViewModel { BoolValue = true };
+            var target = CreateTargetWithSource(data, o => !o.BoolValue, mode: BindingMode.TwoWay);
+
+            target.Bool = true;
+
+            Assert.False(data.BoolValue);
+        }
+
+        [Fact]
+        public void Can_Set_Negated_Value_In_Path()
+        {
+            var data = new ViewModel { Next = new() { BoolValue = true } };
+            var target = CreateTargetWithSource(data, o => !o.Next!.BoolValue, mode: BindingMode.TwoWay);
+
+            target.Bool = true;
+
+            Assert.False(data.Next.BoolValue);
+        }
+
+        [Fact]
+        public void Can_Set_Double_Negated_Value()
+        {
+            var data = new ViewModel { BoolValue = true };
+            var target = CreateTargetWithSource(data, o => !!o.BoolValue, mode: BindingMode.TwoWay);
+
+            target.Bool = false;
+
+            Assert.False(data.BoolValue);
+        }
+
+        [Fact]
+        public void Can_Set_Double_Negated_Value_In_Path()
+        {
+            var data = new ViewModel { Next = new() { BoolValue = true } };
+            var target = CreateTargetWithSource(data, o => !!o.Next!.BoolValue, mode: BindingMode.TwoWay);
+
+            target.Bool = false;
+
+            Assert.False(data.Next.BoolValue);
+        }
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Observable.cs b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Observable.cs
new file mode 100644
index 000000000..5665553aa
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Observable.cs
@@ -0,0 +1,89 @@
+using System;
+using System.Reactive.Subjects;
+using Avalonia.UnitTests;
+using Xunit;
+
+namespace Avalonia.Base.UnitTests.Data.Core;
+
+public partial class BindingExpressionTests
+{
+    [Fact]
+    public void Should_Not_Get_Observable_Value_Without_Streaming()
+    {
+        using var sync = UnitTestSynchronizationContext.Begin();
+        var source = new BehaviorSubject<string>("foo");
+        var data = new { Foo = source };
+        var target = CreateTargetWithSource(data, o => o.Foo);
+        
+        Assert.Same(source, target.Object);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Get_Simple_Observable_Value()
+    {
+        using var sync = UnitTestSynchronizationContext.Begin();
+        var source = new BehaviorSubject<string>("foo");
+        var data = new { Foo = source };
+        var target = CreateTargetWithSource(data, o => o.Foo.StreamBinding());
+
+        Assert.Equal("foo", target.String);
+
+        source.OnNext("bar");
+
+        Assert.Equal("bar", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Get_Property_Value_From_Observable()
+    {
+        using var sync = UnitTestSynchronizationContext.Begin();
+        var source = new BehaviorSubject<ViewModel>(new() { StringValue = "foo" });
+        var data = new ViewModel { NextObservable = source };
+        var target = CreateTargetWithSource(data, o => o.NextObservable.StreamBinding().StringValue);
+
+        Assert.Equal("foo", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Get_Simple_Observable_Value_With_DataValidation_Enabled()
+    {
+        using var sync = UnitTestSynchronizationContext.Begin();
+        var source = new BehaviorSubject<string>("foo");
+        var data = new { Foo = source };
+        var target = CreateTargetWithSource(
+            data,
+            o => o.Foo.StreamBinding(),
+            enableDataValidation: true);
+
+        Assert.Equal("foo", target.String);
+
+        source.OnNext("bar");
+
+        Assert.Equal("bar", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Work_With_Value_Type()
+    {
+        using var sync = UnitTestSynchronizationContext.Begin();
+        var source = new BehaviorSubject<int>(1);
+        var data = new { Foo = source };
+        var target = CreateTargetWithSource(data, o => o.Foo.StreamBinding());
+
+        Assert.Equal(1, target.Int);
+
+        source.OnNext(42);
+
+        Assert.Equal(42, target.Int);
+
+        GC.KeepAlive(data);
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Property.cs b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Property.cs
new file mode 100644
index 000000000..225b2be45
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Property.cs
@@ -0,0 +1,238 @@
+using System;
+using Avalonia.Controls;
+using Avalonia.Data;
+using Xunit;
+
+#nullable enable
+
+namespace Avalonia.Base.UnitTests.Data.Core
+{
+    public partial class BindingExpressionTests
+    {
+        [Fact]
+        public void Should_Get_Simple_Property_Value()
+        {
+            var data = new { Foo = "foo" };
+            var target = CreateTargetWithSource(data, o => o.Foo);
+
+            Assert.Equal("foo", target.String);
+
+            GC.KeepAlive(data);
+        }
+
+        [Fact]
+        public void Should_Get_Simple_Property_Value_Null()
+        {
+            var data = new { Foo = (string?)null };
+            var target = CreateTargetWithSource(data, o => o.Foo);
+
+            Assert.Null(target.String);
+
+            GC.KeepAlive(data);
+        }
+
+        [Fact]
+        public void Should_Get_Simple_Property_From_Base_Class()
+        {
+            var data = new DerivedViewModel { StringValue = "foo" };
+            var target = CreateTargetWithSource(data, o => o.StringValue);
+
+            Assert.Equal("foo", target.String);
+
+            GC.KeepAlive(data);
+        }
+
+        [Fact]
+        public void Should_Get_Simple_Property_Chain()
+        {
+            var data = new { Foo = new { Bar = new { Baz = "baz" } } };
+            var target = CreateTargetWithSource(data, o => o.Foo.Bar.Baz);
+
+            Assert.Equal("baz", target.String);
+
+            GC.KeepAlive(data);
+        }
+
+        [Fact]
+        public void Should_Track_Simple_Property_Value()
+        {
+            var data = new ViewModel { StringValue = "foo" };
+            var target = CreateTargetWithSource(data, o => o.StringValue);
+
+            Assert.Equal("foo", target.String);
+
+            data.StringValue = "bar";
+
+            Assert.Equal("bar", target.String);
+
+            GC.KeepAlive(data);
+        }
+
+        [Fact]
+        public void PropertyChangedEventArgs_With_Null_PropertyName_Should_Trigger_Update()
+        {
+            var data = new ViewModel { StringValue = "foo" };
+            var target = CreateTargetWithSource(data, o => o.StringValue);
+
+            Assert.Equal("foo", target.String);
+
+            data.SetStringValueWithoutRaising("bar");
+
+            Assert.Equal("foo", target.String);
+
+            data.RaisePropertyChanged(null);
+
+            Assert.Equal("bar", target.String);
+
+            GC.KeepAlive(data);
+        }
+
+        [Fact]
+        public void Should_Track_End_Of_Property_Chain_Changing()
+        {
+            var data = new ViewModel { Next = new() { StringValue = "bar" } };
+            var target = CreateTargetWithSource(data, o => o.Next!.StringValue);
+
+            Assert.Equal("bar", target.String);
+
+            data.Next.StringValue = "baz";
+
+            Assert.Equal("baz", target.String);
+
+            data.Next.StringValue = null;
+
+            Assert.Null(target.String);
+
+            GC.KeepAlive(data);
+        }
+
+        [Fact]
+        public void Should_Track_Property_Chain_Changing()
+        {
+            var data = new ViewModel { Next = new() { StringValue = "bar" } };
+            var target = CreateTargetWithSource(data, o => o.Next!.StringValue);
+            var old = data.Next;
+
+            Assert.Equal("bar", target.String);
+
+            data.Next = new() { StringValue = "baz" };
+
+            Assert.Equal("baz", target.String);
+
+            data.Next = new() { StringValue = null };
+
+            Assert.Null(target.String);
+
+            GC.KeepAlive(data);
+        }
+
+        [Fact]
+        public void Should_Track_Property_Chain_Breaking_With_Null_Then_Mending()
+        {
+            var data = new ViewModel
+            {
+                Next = new()
+                {
+                    Next = new()
+                    {
+                        StringValue = "bar"
+                    }
+                }
+            };
+
+            var target = CreateTargetWithSource(data, o => o.Next!.Next!.StringValue);
+
+            Assert.Equal("bar", target.String);
+
+            var old = data.Next;
+            data.Next = null;
+
+            Assert.Null(target.String);
+
+            data.Next = old;
+
+            Assert.Equal("bar", target.String);
+
+            GC.KeepAlive(data);
+        }
+
+        [Fact]
+        public void Should_Track_Property_Chain_Breaking_With_Missing_Member_Then_Mending()
+        {
+            var data = new ViewModel { ObjectValue = new ViewModel { StringValue = "bar" } };
+            var target = CreateTargetWithSource(data, o => (o.ObjectValue as ViewModel)!.StringValue);
+
+            Assert.Equal("bar", target.String);
+
+            var old = data.ObjectValue;
+            data.ObjectValue = new { MissingMember = "Yes" };
+
+            Assert.Null(target.String);
+
+            data.ObjectValue = old;
+
+            Assert.Equal("bar", target.String);
+
+            GC.KeepAlive(data);
+        }
+
+        [Fact]
+        public void Should_Not_Keep_Source_Alive()
+        {
+            Func<(TargetClass, WeakReference<ViewModel>)> run = () =>
+            {
+                var source = new ViewModel { StringValue = "foo" };
+                var target = CreateTargetWithSource(source, o => o.StringValue);
+                return (target, new(source));
+            };
+
+            var result = run();
+
+            // Mono trickery
+            GC.Collect(2);
+            GC.WaitForPendingFinalizers();
+            GC.WaitForPendingFinalizers();
+            GC.Collect(2);
+
+            Assert.False(result.Item2.TryGetTarget(out _));
+        }
+
+        [Fact]
+        public void Should_Not_Throw_Exception_On_Duplicate_Properties()
+        {
+            // Repro of https://github.com/AvaloniaUI/Avalonia/issues/4733.
+            var source = new DerivedViewModelWithDuplicateProperty { StringValue = "NewName" };
+            var target = CreateTargetWithSource(source, x => x.StringValue);
+
+            Assert.Equal("NewName", target.String);
+        }
+
+        [Fact]
+        public void Can_Convert_Int_To_Enum_Two_Way()
+        {
+            var data = new ViewModel { IntValue = 1 };
+            var target = CreateTargetWithSource(
+                data,
+                o => o.IntValue,
+                mode: BindingMode.TwoWay,
+                targetProperty: DockPanel.DockProperty);
+
+            Assert.Equal(Dock.Bottom, DockPanel.GetDock(target));
+
+            DockPanel.SetDock(target, Dock.Right);
+
+            Assert.Equal(2, data.IntValue);
+
+            GC.KeepAlive(data);
+        }
+
+        private class DerivedViewModel : ViewModel
+        {
+        }
+
+        private class DerivedViewModelWithDuplicateProperty : ViewModel
+        {
+            public new string? StringValue { get; set; }
+        }
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.SetValue.cs b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.SetValue.cs
new file mode 100644
index 000000000..04f697c92
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.SetValue.cs
@@ -0,0 +1,232 @@
+using System;
+using System.Globalization;
+using Avalonia.Controls;
+using Avalonia.Data;
+using Avalonia.Data.Converters;
+using Avalonia.UnitTests;
+using Xunit;
+
+#nullable enable
+
+namespace Avalonia.Base.UnitTests.Data.Core;
+
+public abstract partial class BindingExpressionTests
+{
+    [Fact]
+    public void Should_Write_Value_To_Source()
+    {
+        var data = new ViewModel { StringValue = "foo" };
+        var target = CreateTargetWithSource(data, o => o.StringValue, mode: BindingMode.TwoWay);
+
+        target.String = "bar";
+
+        Assert.Equal("bar", data.StringValue);
+    }
+
+    [Fact]
+    public void Should_Write_Value_To_Attached_Property_On_Source()
+    {
+        var data = new AvaloniaObject();
+        var target = CreateTargetWithSource(
+            data, 
+            o => o[DockPanel.DockProperty],
+            mode: BindingMode.TwoWay,
+            targetProperty: Control.TagProperty);
+
+        target.Tag = Dock.Right;
+
+        Assert.Equal(Dock.Right, data[DockPanel.DockProperty]);
+    }
+
+    [Fact]
+    public void Should_Write_Indexed_Value_To_Source()
+    {
+        var data = new { Foo = new[] { "foo" } };
+        var target = CreateTargetWithSource(data, o => o.Foo[0], mode: BindingMode.TwoWay);
+
+        target.String = "bar";
+
+        Assert.Equal("bar", data.Foo[0]);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Write_Value_To_Source_On_Simple_Property_Chain()
+    {
+        var data = new ViewModel { Next = new() { StringValue = "foo" } };
+        var target = CreateTargetWithSource(data, o => o.Next!.StringValue, mode: BindingMode.TwoWay);
+
+        target.String = "bar";
+
+        Assert.Equal("bar", data.Next!.StringValue);
+    }
+
+    [Fact]
+    public void Target_Value_Can_Be_Set_On_Broken_Chain()
+    {
+        var data = new ViewModel { Next = new() { StringValue = "foo" } };
+        var target = CreateTargetWithSource(data, o => o.Next!.StringValue, mode: BindingMode.TwoWay);
+
+        data.Next = null;
+        target.String = "bar";
+
+        Assert.Equal("bar", target.String);
+    }
+
+    [Fact]
+    public void Should_Use_Converter_When_Writing_To_Source()
+    {
+        var data = new ViewModel { StringValue = "foo" };
+        var target = CreateTargetWithSource(
+            data,
+            o => o.StringValue,
+            mode: BindingMode.TwoWay,
+            converter: new CaseConverter());
+
+        target.String = "BaR";
+        Assert.Equal("bar", data.StringValue);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void TwoWay_Binding_Should_Not_Write_Unchanged_Value_Back_To_Property_With_Converter()
+    {
+        var data = new Cat();
+        var target = CreateTargetWithSource(
+            data,
+            o => o.WhiskerCount,
+            converter: new CaseConverter(),
+            mode: BindingMode.TwoWay);
+
+        Assert.Equal(4, target.Int);
+        Assert.Equal(9, data.Lives);
+
+        data.WhiskerCount = 3;
+
+        Assert.Equal(3, target.Int);
+        Assert.Equal(8, data.Lives);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Setter_Should_Convert_Double_To_String()
+    {
+        var data = new ViewModel { StringValue = $"{5.6}" };
+        var target = CreateTargetWithSource(
+            data, 
+            o => o.StringValue, 
+            mode: BindingMode.TwoWay,
+            targetProperty: TargetClass.DoubleProperty);
+
+        target.Double = 6.7;
+
+        Assert.Equal($"{6.7}", data.StringValue);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Setter_Should_Convert_String_To_Double()
+    {
+        var data = new ViewModel { DoubleValue = 5.6 };
+        var target = CreateTargetWithSource(
+            data, 
+            o => o.DoubleValue,
+            mode: BindingMode.TwoWay,
+            targetProperty: TargetClass.StringProperty);
+
+        target.String = $"{6.7}";
+
+        Assert.Equal(6.7, data.DoubleValue);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Setting_Invalid_Double_String_Should_Not_Change_Target()
+    {
+        var data = new ViewModel { DoubleValue = 5.6 };
+        var target = CreateTargetWithSource(
+            data,
+            o => o.DoubleValue,
+            mode: BindingMode.TwoWay,
+            targetProperty: TargetClass.StringProperty);
+
+        target.String = "foo";
+
+        Assert.Equal(5.6, data.DoubleValue);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Setting_Invalid_Double_String_Should_Use_FallbackValue()
+    {
+        var data = new ViewModel { DoubleValue = 5.6 };
+        var target = CreateTargetWithSource(
+            data,
+            o => o.DoubleValue,
+            mode: BindingMode.TwoWay,
+            fallbackValue: 9.8,
+            targetProperty: TargetClass.StringProperty);
+
+        target.String = "foo";
+
+        Assert.Equal(9.8, data.DoubleValue);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Pass_ConverterParameter_To_Converter_ConvertBack()
+    {
+        var data = new ViewModel { StringValue = "Initial" };
+        var converter = new PrefixConverter();
+        var target = CreateTargetWithSource(
+            data,
+            o => o.StringValue,
+            converter: converter,
+            converterParameter: "foo",
+            mode: BindingMode.TwoWay);
+
+        target.String = "fooBar";
+
+        Assert.Equal("Bar", data.StringValue);
+    }
+
+    private class Cat : NotifyingBase
+    {
+        private int _whiskerCount = 4;
+
+        public int WhiskerCount
+        {
+            get => _whiskerCount;
+            set
+            {
+                _whiskerCount = value;
+                RaisePropertyChanged(nameof(WhiskerCount));
+                --Lives;
+            }
+        }
+
+        public int Lives { get; private set; } = 9;
+    }
+
+    private class CaseConverter : IValueConverter
+    {
+        public static readonly CaseConverter Instance = new();
+
+        public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+        {
+            return value?.ToString()?.ToUpper();
+        }
+
+        public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+        {
+            return value?.ToString()?.ToLower();
+        }
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Task.cs b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Task.cs
new file mode 100644
index 000000000..9cbc52207
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.Task.cs
@@ -0,0 +1,128 @@
+using System;
+using System.Threading.Tasks;
+using Avalonia.Data;
+using Avalonia.UnitTests;
+using Xunit;
+
+#nullable enable
+
+namespace Avalonia.Base.UnitTests.Data.Core;
+
+public partial class BindingExpressionTests
+{
+    [Fact]
+    public void Should_Not_Get_Task_Result_Without_StreamBinding()
+    {
+        using var sync = UnitTestSynchronizationContext.Begin();
+        var tcs = new TaskCompletionSource<string>();
+        var data = new { Foo = tcs.Task };
+        var target = CreateTargetWithSource(data, o => o.Foo);
+
+        Assert.Null(target.String);
+
+        tcs.SetResult("foo");
+        sync.ExecutePostedCallbacks();
+
+        Assert.Null(target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Get_Completed_Task_Value()
+    {
+        using var sync = UnitTestSynchronizationContext.Begin();
+        var data = new { Foo = Task.FromResult("foo") };
+        var target = CreateTargetWithSource(data, o => o.Foo.StreamBinding());
+
+        Assert.Equal("foo", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Get_Property_Value_From_Task()
+    {
+        using var sync = UnitTestSynchronizationContext.Begin();
+        var tcs = new TaskCompletionSource<ViewModel>();
+        var data = new ViewModel { NextTask = tcs.Task };
+        var target = CreateTargetWithSource(data, o => o.NextTask.StreamBinding().StringValue);
+
+        tcs.SetResult(new ViewModel { StringValue = "foo" });
+        sync.ExecutePostedCallbacks();
+
+        Assert.Equal("foo", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Update_Data_Validation_On_Task_Exception()
+    {
+        using var sync = UnitTestSynchronizationContext.Begin();
+        var tcs = new TaskCompletionSource<string>();
+        var data = new { Foo = tcs.Task };
+        var target = CreateTargetWithSource(
+            data,
+            o => o.Foo.StreamBinding(),
+            enableDataValidation: true);
+
+        tcs.SetException(new NotSupportedException());
+        sync.ExecutePostedCallbacks();
+
+        AssertBindingError(
+            target,
+            TargetClass.StringProperty,
+            new BindingChainException("Specified method is not supported.", "Foo^", "^"),
+            BindingErrorType.Error);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Update_Data_Validation_On_Faulted_Task()
+    {
+        using var sync = UnitTestSynchronizationContext.Begin();
+        var data = new { Foo = TaskFromException(new NotSupportedException()) };
+        var target = CreateTargetWithSource(
+            data,
+            o => o.Foo.StreamBinding(),
+            enableDataValidation: true);
+
+        AssertBindingError(
+            target,
+            TargetClass.StringProperty,
+            new BindingChainException("Specified method is not supported.", "Foo^", "^"),
+            BindingErrorType.Error);
+
+        GC.KeepAlive(data);
+    }
+
+    [Fact]
+    public void Should_Get_Simple_Task_Value_With_Data_DataValidation_Enabled()
+    {
+        using var sync = UnitTestSynchronizationContext.Begin();
+        var tcs = new TaskCompletionSource<string>();
+        var data = new { Foo = tcs.Task };
+        var target = CreateTargetWithSource(
+            data,
+            o => o.Foo.StreamBinding(),
+            enableDataValidation: true);
+
+        tcs.SetResult("foo");
+        sync.ExecutePostedCallbacks();
+
+        // What does it mean to have data validation on a Task? Without a use-case it's
+        // hard to know what to do here so for the moment the value is returned.
+        Assert.Equal("foo", target.String);
+
+        GC.KeepAlive(data);
+    }
+
+    private static Task<string> TaskFromException(Exception e)
+    {
+        var tcs = new TaskCompletionSource<string>();
+        tcs.SetException(e);
+        return tcs.Task;
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.UpdateSourceTrigger.cs b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.UpdateSourceTrigger.cs
new file mode 100644
index 000000000..b1e21467f
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.UpdateSourceTrigger.cs
@@ -0,0 +1,113 @@
+using Avalonia.Data;
+using Avalonia.UnitTests;
+using Xunit;
+
+namespace Avalonia.Base.UnitTests.Data.Core
+{
+    public partial class BindingExpressionTests
+    {
+        [Fact]
+        public void TwoWay_PropertyChanged_Should_Update_Source_On_Property_Changed()
+        {
+            var data = new ViewModel { StringValue = "foo" };
+            var target = CreateTargetWithSource(data, o => o.StringValue, mode: BindingMode.TwoWay);
+
+            Assert.Equal("foo", target.String);
+            Assert.Equal("foo", data.StringValue);
+
+            target.String = "bar";
+
+            Assert.Equal("bar", target.String);
+            Assert.Equal("bar", data.StringValue);
+        }
+
+        [Fact]
+        public void TwoWay_LostFocus_Should_Update_Source_On_Lost_Focus()
+        {
+            using var app = StartWithFocusSupport();
+            var data = new ViewModel { StringValue = "foo" };
+            var target = CreateTargetWithSource(
+                data,
+                o => o.StringValue,
+                mode: BindingMode.TwoWay,
+                updateSourceTrigger: UpdateSourceTrigger.LostFocus);
+            var root = new TestRoot(target) { Focusable = true };
+
+            target.Focus();
+
+            Assert.Equal("foo", target.String);
+            Assert.Equal("foo", data.StringValue);
+
+            target.String = "bar";
+
+            Assert.Equal("bar", target.String);
+            Assert.Equal("foo", data.StringValue);
+
+            root.Focus();
+
+            Assert.Equal("bar", target.String);
+            Assert.Equal("bar", data.StringValue);
+        }
+
+        [Fact]
+        public void OneWayToSource_LostFocus_Should_Update_Source_On_Lost_Focus()
+        {
+            using var app = StartWithFocusSupport();
+            var data = new ViewModel { StringValue = "foo" };
+            var target = CreateTargetWithSource(
+                data,
+                o => o.StringValue,
+                mode: BindingMode.OneWayToSource,
+                updateSourceTrigger: UpdateSourceTrigger.LostFocus);
+            var root = new TestRoot(target) { Focusable = true };
+
+            target.Focus();
+
+            Assert.Null(target.String);
+            Assert.Equal("foo", data.StringValue);
+
+            target.String = "bar";
+
+            Assert.Equal("bar", target.String);
+            Assert.Equal("foo", data.StringValue);
+
+            root.Focus();
+
+            Assert.Equal("bar", target.String);
+            Assert.Equal("bar", data.StringValue);
+        }
+
+        [Fact]
+        public void TwoWay_Explicit_Should_Update_Source_On_Call_To_UpdateSource()
+        {
+            using var app = StartWithFocusSupport();
+            var data = new ViewModel { StringValue = "foo" };
+            var (target, expression) = CreateTargetAndExpression<ViewModel, string?>(
+                o => o.StringValue,
+                mode: BindingMode.TwoWay,
+                source: data,
+                updateSourceTrigger: UpdateSourceTrigger.Explicit);
+            var root = new TestRoot(target) { Focusable = true };
+
+            target.Focus();
+
+            Assert.Equal("foo", target.String);
+            Assert.Equal("foo", data.StringValue);
+
+            target.String = "bar";
+
+            Assert.Equal("bar", target.String);
+            Assert.Equal("foo", data.StringValue);
+
+            root.Focus();
+
+            Assert.Equal("bar", target.String);
+            Assert.Equal("foo", data.StringValue);
+
+            expression.UpdateSource();
+
+            Assert.Equal("bar", target.String);
+            Assert.Equal("bar", data.StringValue);
+        }
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.cs b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.cs
index f56b188a2..6a83f3413 100644
--- a/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.cs
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/BindingExpressionTests.cs
@@ -1,381 +1,430 @@
 using System;
 using System.Collections.Generic;
 using System.Globalization;
-using System.Reactive.Linq;
+using System.Linq.Expressions;
 using System.Threading.Tasks;
+using Avalonia.Controls;
 using Avalonia.Data;
 using Avalonia.Data.Converters;
 using Avalonia.Data.Core;
+using Avalonia.Data.Core.ExpressionNodes;
+using Avalonia.Markup.Parsers;
 using Avalonia.UnitTests;
-using Moq;
-using Xunit;
+using Avalonia.Utilities;
 
-namespace Avalonia.Base.UnitTests.Data.Core
+#nullable enable
+
+namespace Avalonia.Base.UnitTests.Data.Core;
+
+[InvariantCulture]
+public abstract partial class BindingExpressionTests
 {
-    [InvariantCulture]
-    public class BindingExpressionTests
+    public class Reflection : BindingExpressionTests
     {
-        [Fact]
-        public async Task Should_Get_Simple_Property_Value()
+        private protected override (TargetClass, BindingExpression) CreateTargetCore<TIn, TOut>(
+            Expression<Func<TIn, TOut>> expression,
+            AvaloniaProperty targetProperty,
+            IValueConverter? converter,
+            object? converterParameter,
+            object? dataContext,
+            bool enableDataValidation,
+            Optional<object?> fallbackValue,
+            BindingMode mode,
+            RelativeSource? relativeSource,
+            Optional<TIn> source,
+            object? targetNullValue,
+            UpdateSourceTrigger updateSourceTrigger)
         {
-            var data = new Class1 { StringValue = "foo" };
-            var target = new BindingExpression(ExpressionObserver.Create(data, o => o.StringValue), typeof(string));
-            var result = await target.Take(1);
+            var target = new TargetClass { DataContext = dataContext };
+            var (path, resolver) = BindingPathFromExpressionBuilder.Build(expression);
+            var fallback = fallbackValue.HasValue ? fallbackValue.Value : AvaloniaProperty.UnsetValue;
+            List<ExpressionNode>? nodes = null;
 
-            Assert.Equal("foo", result);
+            if (relativeSource is not null && relativeSource.Mode is not RelativeSourceMode.Self)
+                throw new NotImplementedException();
 
-            GC.KeepAlive(data);
+            if (!string.IsNullOrEmpty(path))
+            {
+                var reader = new CharacterReader(path.AsSpan());
+                var (astNodes, sourceMode) = BindingExpressionGrammar.Parse(ref reader);
+                nodes = ExpressionNodeFactory.CreateFromAst(astNodes, resolver, null, out _);
+            }
+
+            if (!source.HasValue && relativeSource is null)
+            {
+                nodes ??= new();
+                nodes.Insert(0, new DataContextNode());
+            }
+
+            var bindingExpression = new BindingExpression(
+                source.HasValue ? source.Value : target,
+                nodes,
+                fallback,
+                converter: converter,
+                converterParameter: converterParameter,
+                enableDataValidation: enableDataValidation,
+                mode: mode,
+                targetNullValue: targetNullValue,
+                targetTypeConverter: TargetTypeConverter.GetReflectionConverter(),
+                updateSourceTrigger: updateSourceTrigger);
+
+            target.GetValueStore().AddBinding(targetProperty, bindingExpression);
+            return (target, bindingExpression);
+        }
+    }
+
+    public class Compiled : BindingExpressionTests
+    {
+        private protected override (TargetClass, BindingExpression) CreateTargetCore<TIn, TOut>(
+            Expression<Func<TIn, TOut>> expression,
+            AvaloniaProperty targetProperty,
+            IValueConverter? converter,
+            object? converterParameter,
+            object? dataContext,
+            bool enableDataValidation,
+            Optional<object?> fallbackValue,
+            BindingMode mode,
+            RelativeSource? relativeSource,
+            Optional<TIn> source,
+            object? targetNullValue,
+            UpdateSourceTrigger updateSourceTrigger)
+        {
+            var target = new TargetClass { DataContext = dataContext };
+            var nodes = new List<ExpressionNode>();
+            var fallback = fallbackValue.HasValue ? fallbackValue.Value : AvaloniaProperty.UnsetValue;
+            var path = CompiledBindingPathFromExpressionBuilder.Build(expression, enableDataValidation);
+
+            if (relativeSource is not null && relativeSource.Mode is not RelativeSourceMode.Self)
+                throw new NotImplementedException();
+
+            path.BuildExpression(nodes, out var _);
+
+            if (!source.HasValue && relativeSource is null)
+                nodes.Insert(0, new DataContextNode());
+
+            var bindingExpression = new BindingExpression(
+                source.HasValue ? source.Value : target,
+                nodes,
+                fallback,
+                converter: converter,
+                converterParameter: converterParameter,
+                enableDataValidation: enableDataValidation,
+                mode: mode,
+                targetNullValue: targetNullValue,
+                targetTypeConverter: TargetTypeConverter.GetReflectionConverter(),
+                updateSourceTrigger: updateSourceTrigger);
+            target.GetValueStore().AddBinding(targetProperty, bindingExpression);
+            return (target, bindingExpression);
+        }
+    }
+
+    protected TargetClass CreateTarget<TIn, TOut>(
+        Expression<Func<TIn, TOut>> expression,
+        AvaloniaProperty? targetProperty = null,
+        IValueConverter? converter = null,
+        object? converterParameter = null,
+        object? dataContext = null,
+        bool enableDataValidation = false,
+        Optional<object?> fallbackValue = default,
+        BindingMode mode = BindingMode.OneWay,
+        RelativeSource? relativeSource = null,
+        Optional<TIn> source = default,
+        object? targetNullValue = null)
+            where TIn : class?
+    {
+        var (target, _) = CreateTargetAndExpression(
+            expression,
+            targetProperty,
+            converter,
+            converterParameter,
+            dataContext,
+            enableDataValidation,
+            fallbackValue,
+            mode,
+            relativeSource,
+            source,
+            targetNullValue);
+        return target;
+    }
+
+    protected TargetClass CreateTargetWithSource<TIn, TOut>(
+        TIn source,
+        Expression<Func<TIn, TOut>> expression,
+        AvaloniaProperty? targetProperty = null,
+        IValueConverter? converter = null,
+        object? converterParameter = null,
+        bool enableDataValidation = false,
+        Optional<object?> fallbackValue = default,
+        BindingMode mode = BindingMode.OneWay,
+        RelativeSource? relativeSource = null,
+        object? targetNullValue = null,
+        UpdateSourceTrigger updateSourceTrigger = UpdateSourceTrigger.PropertyChanged)
+            where TIn : class?
+    {
+        var (target, _) = CreateTargetAndExpression(
+            expression,
+            targetProperty,
+            converter,
+            converterParameter,
+            null,
+            enableDataValidation,
+            fallbackValue,
+            mode,
+            relativeSource,
+            source,
+            targetNullValue,
+            updateSourceTrigger);
+        return target;
+    }
+
+    private protected (TargetClass, BindingExpression) CreateTargetAndExpression<TIn, TOut>(
+        Expression<Func<TIn, TOut>> expression,
+        AvaloniaProperty? targetProperty = null,
+        IValueConverter? converter = null,
+        object? converterParameter = null,
+        object? dataContext = null,
+        bool enableDataValidation = false,
+        Optional<object?> fallbackValue = default,
+        BindingMode mode = BindingMode.OneWay,
+        RelativeSource? relativeSource = null,
+        Optional<TIn> source = default,
+        object? targetNullValue = null,
+        UpdateSourceTrigger updateSourceTrigger = UpdateSourceTrigger.PropertyChanged)
+            where TIn : class?
+    {
+        targetProperty ??= typeof(TOut) switch
+        {
+            var t when t == typeof(bool) => TargetClass.BoolProperty,
+            var t when t == typeof(double) => TargetClass.DoubleProperty,
+            var t when t == typeof(int) => TargetClass.IntProperty,
+            var t when t == typeof(string) => TargetClass.StringProperty,
+            _ => TargetClass.ObjectProperty,
+        };
+
+        return CreateTargetCore(
+            expression,
+            targetProperty,
+            converter,
+            converterParameter,
+            dataContext,
+            enableDataValidation,
+            fallbackValue,
+            mode,
+            relativeSource,
+            source,
+            targetNullValue,
+            updateSourceTrigger);
+    }
+
+    private protected abstract (TargetClass, BindingExpression) CreateTargetCore<TIn, TOut>(
+        Expression<Func<TIn, TOut>> expression,
+        AvaloniaProperty targetProperty,
+        IValueConverter? converter,
+        object? converterParameter,
+        object? dataContext,
+        bool enableDataValidation,
+        Optional<object?> fallbackValue,
+        BindingMode mode,
+        RelativeSource? relativeSource,
+        Optional<TIn> source,
+        object? targetNullValue,
+        UpdateSourceTrigger updateSourceTrigger)
+            where TIn : class?;
+
+    private static IDisposable StartWithFocusSupport()
+    {
+        return UnitTestApplication.Start(TestServices.RealFocus);
+    }
+
+    protected class ViewModel : NotifyingBase
+    {
+        private bool _boolValue;
+        private double _doubleValue;
+        private int _intValue;
+        private object? _objectValue;
+        private string? _stringValue;
+        private ViewModel? _next;
+        private IObservable<ViewModel>? _nextObservable;
+        private Task<ViewModel>? _nextTask;
+
+        public bool BoolValue
+        {
+            get => _boolValue;
+            set { _boolValue = value; RaisePropertyChanged(); }
         }
 
-        [Fact]
-        public void Should_Set_Simple_Property_Value()
+        public int IntValue
         {
-            var data = new Class1 { StringValue = "foo" };
-            var target = new BindingExpression(ExpressionObserver.Create(data, o => o.StringValue), typeof(string));
-
-            target.OnNext("bar");
-
-            Assert.Equal("bar", data.StringValue);
-
-            GC.KeepAlive(data);
+            get => _intValue;
+            set { _intValue = value; RaisePropertyChanged(); }
         }
 
-        [Fact]
-        public void Should_Set_Indexed_Value()
+        public double DoubleValue
         {
-            var data = new { Foo = new[] { "foo" } };
-            var target = new BindingExpression(ExpressionObserver.Create(data, o => o.Foo[0]), typeof(string));
-
-            target.OnNext("bar");
-
-            Assert.Equal("bar", data.Foo[0]);
-
-            GC.KeepAlive(data);
+            get => _doubleValue;
+            set { _doubleValue = value; RaisePropertyChanged(); }
         }
 
-        [Fact]
-        public async Task Should_Convert_Get_String_To_Double()
+        public object? ObjectValue
         {
-            var data = new Class1 { StringValue = $"{5.6}" };
-            var target = new BindingExpression(ExpressionObserver.Create(data, o => o.StringValue), typeof(double));
-            var result = await target.Take(1);
-
-            Assert.Equal(5.6, result);
-
-            GC.KeepAlive(data);
+            get => _objectValue;
+            set { _objectValue = value; RaisePropertyChanged(); }
         }
 
-        [Fact]
-        public async Task Getting_Invalid_Double_String_Should_Return_BindingError()
+        public string? StringValue
         {
-            var data = new Class1 { StringValue = "foo" };
-            var target = new BindingExpression(ExpressionObserver.Create(data, o => o.StringValue), typeof(double));
-            var result = await target.Take(1);
-
-            Assert.IsType<BindingNotification>(result);
-
-            GC.KeepAlive(data);
+            get => _stringValue;
+            set { _stringValue = value; RaisePropertyChanged(); }
         }
 
-        [Fact]
-        public void Should_Convert_Set_String_To_Double()
+        public ViewModel? Next
         {
-            var data = new Class1 { StringValue = $"{5.6}" };
-            var target = new BindingExpression(ExpressionObserver.Create(data, o => o.StringValue), typeof(double));
-
-            target.OnNext(6.7);
-
-            Assert.Equal($"{6.7}", data.StringValue);
-
-            GC.KeepAlive(data);
+            get => _next;
+            set { _next = value; RaisePropertyChanged(); }
         }
 
-        [Fact]
-        public async Task Should_Convert_Get_Double_To_String()
+        public IObservable<ViewModel>? NextObservable
         {
-            var data = new Class1 { DoubleValue = 5.6 };
-            var target = new BindingExpression(ExpressionObserver.Create(data, o => o.DoubleValue), typeof(string));
-            var result = await target.Take(1);
-
-            Assert.Equal($"{5.6}", result);
-
-            GC.KeepAlive(data);
+            get => _nextObservable;
+            set { _nextObservable = value; RaisePropertyChanged(); }
         }
 
-        [Fact]
-        public void Should_Convert_Set_Double_To_String()
+        public Task<ViewModel> NextTask
         {
-            var data = new Class1 { DoubleValue = 5.6 };
-            var target = new BindingExpression(ExpressionObserver.Create(data, o => o.DoubleValue), typeof(string));
-
-            target.OnNext($"{6.7}");
-
-            Assert.Equal(6.7, data.DoubleValue);
-
-            GC.KeepAlive(data);
+            get => _nextTask!;
+            set { _nextTask = value; RaisePropertyChanged(); }
         }
 
-        [Fact]
-        public async Task Should_Return_BindingNotification_With_FallbackValue_For_NonConvertibe_Target_Value()
+        public void SetStringValueWithoutRaising(string value) => _stringValue = value;
+    }
+
+    protected class PodViewModel
+    {
+        public string? StringValue { get; set; }
+    }
+
+    protected class AttachedProperties
+    {
+        public static readonly AttachedProperty<string?> AttachedStringProperty =
+            AvaloniaProperty.RegisterAttached<AttachedProperties, AvaloniaObject, string?>("AttachedString");
+    }
+
+    protected class SourceControl : Control
+    {
+        public static readonly StyledProperty<SourceControl?> NextProperty =
+            AvaloniaProperty.Register<SourceControl, SourceControl?>("Next");
+        public static readonly StyledProperty<string?> StringValueProperty =
+            AvaloniaProperty.Register<SourceControl, string?>("StringValue");
+
+        public SourceControl? Next
         {
-            var data = new Class1 { StringValue = "foo" };
-            var target = new BindingExpression(
-                ExpressionObserver.Create(data, o => o.StringValue),
-                typeof(int),
-                42,
-                AvaloniaProperty.UnsetValue,
-                DefaultValueConverter.Instance,
-                CultureInfo.InvariantCulture);
-            var result = await target.Take(1);
-
-            Assert.Equal(
-                new BindingNotification(
-                    new InvalidCastException("'foo' is not a valid number."),
-                    BindingErrorType.Error,
-                    42),
-                result);
-
-            GC.KeepAlive(data);
+            get => GetValue(NextProperty);
+            set => SetValue(NextProperty, value);
         }
 
-        [Fact]
-        public async Task Should_Return_BindingNotification_With_FallbackValue_For_NonConvertibe_Target_Value_With_Data_Validation()
+        public string? StringValue
         {
-            var data = new Class1 { StringValue = "foo" };
-            var target = new BindingExpression(
-                ExpressionObserver.Create(data, o => o.StringValue, true),
-                typeof(int),
-                42,
-                AvaloniaProperty.UnsetValue,
-                DefaultValueConverter.Instance,
-                CultureInfo.InvariantCulture);
-            var result = await target.Take(1);
-
-            Assert.Equal(
-                new BindingNotification(
-                    new InvalidCastException("'foo' is not a valid number."),
-                    BindingErrorType.Error,
-                    42),
-                result);
-
-            GC.KeepAlive(data);
+            get => GetValue(StringValueProperty);
+            set => SetValue(StringValueProperty, value);
         }
 
-        [Fact]
-        public async Task Should_Return_BindingNotification_For_Invalid_FallbackValue()
+        public string? ClrProperty { get; set; }
+    }
+
+    protected class TargetClass : Control
+    {
+        public static readonly StyledProperty<bool> BoolProperty =
+            AvaloniaProperty.Register<TargetClass, bool>("Bool");
+        public static readonly StyledProperty<double> DoubleProperty =
+            AvaloniaProperty.Register<TargetClass, double>("Double");
+        public static readonly StyledProperty<int> IntProperty =
+            AvaloniaProperty.Register<TargetClass, int>("Int");
+        public static readonly StyledProperty<object?> ObjectProperty =
+            AvaloniaProperty.Register<TargetClass, object?>("Object");
+        public static readonly StyledProperty<string?> StringProperty =
+            AvaloniaProperty.Register<TargetClass, string?>("String");
+
+        static TargetClass()
         {
-            var data = new Class1 { StringValue = "foo" };
-            var target = new BindingExpression(
-                ExpressionObserver.Create(data, o => o.StringValue),
-                typeof(int),
-                "bar",
-                AvaloniaProperty.UnsetValue,
-                DefaultValueConverter.Instance,
-                CultureInfo.InvariantCulture);
-            var result = await target.Take(1);
-
-            Assert.Equal(
-                new BindingNotification(
-                    new AggregateException(
-                        new InvalidCastException("'foo' is not a valid number."),
-                        new InvalidCastException("Could not convert FallbackValue 'bar' to 'System.Int32'")),
-                    BindingErrorType.Error),
-                result);
-
-            GC.KeepAlive(data);
+            FocusableProperty.OverrideDefaultValue<TargetClass>(true);
         }
 
-        [Fact]
-        public async Task Should_Return_BindingNotification_For_Invalid_FallbackValue_With_Data_Validation()
+        public bool Bool
         {
-            var data = new Class1 { StringValue = "foo" };
-            var target = new BindingExpression(
-                ExpressionObserver.Create(data, o => o.StringValue, true),
-                typeof(int),
-                "bar",
-                AvaloniaProperty.UnsetValue,
-                DefaultValueConverter.Instance,
-                CultureInfo.InvariantCulture);
-            var result = await target.Take(1);
-
-            Assert.Equal(
-                new BindingNotification(
-                    new AggregateException(
-                        new InvalidCastException("'foo' is not a valid number."),
-                        new InvalidCastException("Could not convert FallbackValue 'bar' to 'System.Int32'")),
-                    BindingErrorType.Error),
-                result);
-
-            GC.KeepAlive(data);
+            get => GetValue(BoolProperty);
+            set => SetValue(BoolProperty, value);
         }
 
-        [Fact]
-        public void Setting_Invalid_Double_String_Should_Not_Change_Target()
+        public double Double
         {
-            var data = new Class1 { DoubleValue = 5.6 };
-            var target = new BindingExpression(ExpressionObserver.Create(data, o => o.DoubleValue), typeof(string));
-
-            target.OnNext("foo");
-
-            Assert.Equal(5.6, data.DoubleValue);
-
-            GC.KeepAlive(data);
+            get => GetValue(DoubleProperty);
+            set => SetValue(DoubleProperty, value);
         }
 
-        [Fact]
-        public void Setting_Invalid_Double_String_Should_Use_FallbackValue()
+        public int Int
         {
-            var data = new Class1 { DoubleValue = 5.6 };
-            var target = new BindingExpression(
-                ExpressionObserver.Create(data, o => o.DoubleValue),
-                typeof(string),
-                "9.8",
-                AvaloniaProperty.UnsetValue,
-                DefaultValueConverter.Instance,
-                CultureInfo.InvariantCulture);
-
-            target.OnNext("foo");
-
-            Assert.Equal(9.8, data.DoubleValue);
-
-            GC.KeepAlive(data);
+            get => GetValue(IntProperty);
+            set => SetValue(IntProperty, value);
         }
 
-        [Fact]
-        public void Should_Coerce_Setting_UnsetValue_Double_To_Default_Value()
+        public object? Object
         {
-            var data = new Class1 { DoubleValue = 5.6 };
-            var target = new BindingExpression(ExpressionObserver.Create(data, o => o.DoubleValue), typeof(string));
-
-            target.OnNext(AvaloniaProperty.UnsetValue);
-
-            Assert.Equal(0, data.DoubleValue);
-
-            GC.KeepAlive(data);
+            get => GetValue(ObjectProperty);
+            set => SetValue(ObjectProperty, value);
         }
 
-        [Fact]
-        public void Should_Pass_ConverterParameter_To_Convert()
+        public string? String
         {
-            var data = new Class1 { DoubleValue = 5.6 };
-            var converter = new Mock<IValueConverter>();
-
-            var target = new BindingExpression(
-                ExpressionObserver.Create(data, o => o.DoubleValue),
-                typeof(string),
-                converter.Object,
-                CultureInfo.CurrentCulture,
-                converterParameter: "foo");
-
-            target.Subscribe(_ => { });
-
-            converter.Verify(x => x.Convert(5.6, typeof(string), "foo", CultureInfo.CurrentCulture));
-
-            GC.KeepAlive(data);
+            get => GetValue(StringProperty);
+            set => SetValue(StringProperty, value);
         }
 
-        [Fact]
-        public void Should_Pass_ConverterParameter_To_ConvertBack()
+        public Dictionary<AvaloniaProperty, BindingNotification> BindingNotifications { get; } = new();
+
+        public override string ToString() => nameof(TargetClass);
+
+        protected override void UpdateDataValidation(AvaloniaProperty property, BindingValueType state, Exception? error)
         {
-            var data = new Class1 { DoubleValue = 5.6 };
-            var converter = new Mock<IValueConverter>();
-            var target = new BindingExpression(
-                ExpressionObserver.Create(data, o => o.DoubleValue),
-                typeof(string),
-                converter.Object,
-                CultureInfo.CurrentCulture,
-                converterParameter: "foo");
+            base.UpdateDataValidation(property, state, error);
 
-            target.OnNext("bar");
+            var type = state switch
+            {
+                BindingValueType b when b.HasFlag(BindingValueType.BindingError) => BindingErrorType.Error,
+                BindingValueType b when b.HasFlag(BindingValueType.DataValidationError) => BindingErrorType.DataValidationError,
+                _ => BindingErrorType.None,
+            };
 
-            converter.Verify(x => x.ConvertBack("bar", typeof(double), "foo", CultureInfo.CurrentCulture));
+            if (type == BindingErrorType.None || error is null)
+                BindingNotifications.Remove(property);
+            else
+                BindingNotifications[property] = new BindingNotification(error, type);
+        }
+    }
 
-            GC.KeepAlive(data);
+    protected class PrefixConverter : IValueConverter
+    {
+        public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+        {
+            if (targetType != typeof(string))
+                return value;
+
+            var result = value?.ToString() ?? string.Empty;
+            if (parameter is not null)
+                result = parameter.ToString() + result;
+            return result;
         }
 
-        [Fact]
-        public void Should_Handle_DataValidation()
+        public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
         {
-            var data = new Class1 { DoubleValue = 5.6 };
-            var converter = new Mock<IValueConverter>();
-            var target = new BindingExpression(ExpressionObserver.Create(data, o => o.DoubleValue, true), typeof(string));
-            var result = new List<object>();
+            if (targetType != typeof(string) || parameter?.ToString() is not string prefix)
+                return value;
 
-            target.Subscribe(x => result.Add(x));
-            target.OnNext(1.2);
-            target.OnNext($"{3.4}");
-            target.OnNext("bar");
-
-            Assert.Equal(
-                new[]
-                {
-                    new BindingNotification($"{5.6}"),
-                    new BindingNotification($"{1.2}"),
-                    new BindingNotification($"{3.4}"),
-                    new BindingNotification(
-                        new InvalidCastException("'bar' is not a valid number."),
-                        BindingErrorType.Error)
-                },
-                result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Second_Subscription_Should_Fire_Immediately()
-        {
-            var data = new Class1 { StringValue = "foo" };
-            var target = new BindingExpression(ExpressionObserver.Create(data, o => o.StringValue), typeof(string));
-            object result = null;
-
-            target.Subscribe();
-            target.Subscribe(x => result = x);
-
-            Assert.Equal("foo", result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Null_Value_Should_Use_TargetNullValue()
-        {
-            var data = new Class1 { StringValue = "foo" };
-
-            var target = new BindingExpression(
-                ExpressionObserver.Create(data, o => o.StringValue),
-                typeof(string),
-                AvaloniaProperty.UnsetValue,
-                "bar",
-                DefaultValueConverter.Instance,
-                CultureInfo.InvariantCulture);
-
-            object result = null;
-            target.Subscribe(x => result = x);
-
-            Assert.Equal("foo", result);
+            var s = value?.ToString() ?? string.Empty;
             
-            data.StringValue = null;
-            Assert.Equal("bar", result);
-
-            GC.KeepAlive(data);
-        }
-
-        private class Class1 : NotifyingBase
-        {
-            private string _stringValue;
-            private double _doubleValue;
-
-            public string StringValue
-            {
-                get { return _stringValue; }
-                set { _stringValue = value; RaisePropertyChanged(); }
-            }
-
-            public double DoubleValue
-            {
-                get { return _doubleValue; }
-                set { _doubleValue = value; RaisePropertyChanged(); }
-            }
+            if (s.StartsWith(prefix))
+                return s.Substring(prefix.Length);
+            else
+                return value;
         }
     }
 }
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/BindingPathFromExpressionBuilder.cs b/tests/Avalonia.Base.UnitTests/Data/Core/BindingPathFromExpressionBuilder.cs
new file mode 100644
index 000000000..c1dc10bf8
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/BindingPathFromExpressionBuilder.cs
@@ -0,0 +1,257 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Linq.Expressions;
+using System.Reflection;
+using System.Text;
+using Avalonia.Data.Core;
+
+#nullable enable
+
+namespace Avalonia.Base.UnitTests.Data.Core;
+
+internal class BindingPathFromExpressionBuilder : ExpressionVisitor
+{
+    private static readonly PropertyInfo AvaloniaObjectIndexer;
+    private static readonly string IndexerGetterName = "get_Item";
+    private const string MultiDimensionalArrayGetterMethodName = "Get";
+    private readonly LambdaExpression _rootExpression;
+    private readonly StringBuilder _path = new();
+    private Expression? _head;
+    private int _negationCount;
+    private TypeResolver? _resolver;
+
+    public BindingPathFromExpressionBuilder(LambdaExpression expression)
+    {
+        _rootExpression = expression;
+    }
+
+    static BindingPathFromExpressionBuilder()
+    {
+        AvaloniaObjectIndexer = typeof(AvaloniaObject).GetProperty("Item", new[] { typeof(AvaloniaProperty) })!;
+    }
+
+    public static (string, Func<string?, string, Type>?) Build<TIn, TOut>(Expression<Func<TIn, TOut>> expression)
+    {
+        var visitor = new BindingPathFromExpressionBuilder(expression);
+        visitor.Visit(expression);
+        visitor._path.Insert(0, new string('!', visitor._negationCount));
+
+        Func<string?, string, Type>? resolver = null;
+
+        if (visitor._resolver is not null)
+            resolver = visitor._resolver.Resolve;
+
+        return (visitor._path.ToString(), resolver);
+    }
+
+    protected override Expression VisitBinary(BinaryExpression node)
+    {
+        // Indexers require more work since the compiler doesn't generate IndexExpressions:
+        // they weren't in System.Linq.Expressions v1 and so must be generated manually.
+        if (node.NodeType == ExpressionType.ArrayIndex)
+            return Visit(Expression.MakeIndex(node.Left, null, new[] { node.Right }));
+
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitIndex(IndexExpression node)
+    {
+        if (node.Indexer == AvaloniaObjectIndexer)
+        {
+            var property = GetValue<AvaloniaProperty>(node.Arguments[0]);
+            var name = property.Name;
+
+            if (property.IsAttached)
+            {
+                _resolver ??= new();
+                _resolver.Add(property.OwnerType.Name, property.OwnerType);
+                name = $"({property.OwnerType.Name}.{property.Name})";
+            }
+
+            return Add(node.Object, node, name, ".");
+        }
+        else
+        {
+            var indexes = string.Join(',', node.Arguments.Select(GetValue<object>));
+            return Add(node.Object, node, $"[{indexes}]");
+        }
+    }
+
+    protected override Expression VisitMember(MemberExpression node)
+    {
+        if (node.Member.MemberType != MemberTypes.Property)
+            throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+
+        var property = (PropertyInfo)node.Member;
+        return Add(node.Expression, node, property.Name, ".");
+    }
+
+    protected override Expression VisitMethodCall(MethodCallExpression node)
+    {
+        var method = node.Method;
+
+        if (method.Name == IndexerGetterName && node.Object is not null)
+        {
+            var property = TryGetPropertyFromMethod(method);
+            return Visit(Expression.MakeIndex(node.Object, property, node.Arguments));
+        }
+        else if (method.Name == MultiDimensionalArrayGetterMethodName &&
+                 node.Object is not null)
+        {
+            var indexes = string.Join(',', node.Arguments.Select(GetValue<int>));
+            return Add(node.Object, node, $"[{indexes}]");
+        }
+        else if (method.Name.StartsWith(StreamBindingExtensions.StreamBindingName) &&
+                 method.DeclaringType == typeof(StreamBindingExtensions) &&
+                 method.GetGenericArguments() is [Type genericArg])
+        {
+            var instance = node.Method.IsStatic ? node.Arguments[0] : node.Object;
+            return Add(instance, node, "^");
+        }
+
+        throw new ExpressionParseException(0, $"Invalid method call in binding expression: '{node.Method.DeclaringType}.{node.Method.Name}'.");
+    }
+
+    protected override Expression VisitParameter(ParameterExpression node)
+    {
+        if (node == _rootExpression.Parameters[0] && _head is null)
+            _head = node;
+        return base.VisitParameter(node);
+    }
+
+    protected override Expression VisitUnary(UnaryExpression node)
+    {
+        if (node.NodeType == ExpressionType.Not && node.Type == typeof(bool))
+        {
+            ++_negationCount;
+            return _head = base.VisitUnary(node);
+        }
+        else if (node.NodeType == ExpressionType.Convert)
+        {
+            if (node.Operand.Type.IsAssignableFrom(node.Type))
+            {
+                // Ignore inheritance casts 
+                return _head = base.VisitUnary(node);
+            }
+        }
+        else if (node.NodeType == ExpressionType.TypeAs)
+        {
+            // Ignore as operator.
+            return _head = base.VisitUnary(node);
+        }
+
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitBlock(BlockExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override CatchBlock VisitCatchBlock(CatchBlock node)
+    {
+        throw new ExpressionParseException(0, $"Catch blocks are not allowed in binding expressions.");
+    }
+
+    protected override Expression VisitConditional(ConditionalExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitDynamic(DynamicExpression node)
+    {
+        throw new ExpressionParseException(0, $"Dynamic expressions are not allowed in binding expressions.");
+    }
+
+    protected override ElementInit VisitElementInit(ElementInit node)
+    {
+        throw new ExpressionParseException(0, $"Element init expressions are not valid in a binding expression.");
+    }
+
+    protected override Expression VisitGoto(GotoExpression node)
+    {
+        throw new ExpressionParseException(0, $"Goto expressions not supported in binding expressions.");
+    }
+
+    protected override Expression VisitInvocation(InvocationExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitLabel(LabelExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitListInit(ListInitExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitLoop(LoopExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override MemberAssignment VisitMemberAssignment(MemberAssignment node)
+    {
+        throw new ExpressionParseException(0, $"Member assignments not supported in binding expressions.");
+    }
+
+    protected override Expression VisitSwitch(SwitchExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitTry(TryExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitTypeBinary(TypeBinaryExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    private Expression Add(Expression? instance, Expression expression, string pathSegment, string? separator = null)
+    {
+        var visited = Visit(instance);
+
+        if (visited != _head)
+            throw new ExpressionParseException(
+                0,
+                $"Unable to parse '{expression}': expected an instance of '{_head}' but got '{visited}'.");
+
+        if (_path.Length > 0 && !string.IsNullOrEmpty(separator))
+            _path.Append(separator);
+
+        _path.Append(pathSegment);
+        return _head = expression;
+    }
+
+    private static T GetValue<T>(Expression expr)
+    {
+        if (expr is ConstantExpression constant)
+            return (T)constant.Value!;
+        return Expression.Lambda<Func<T>>(expr).Compile(preferInterpretation: true)();
+    }
+
+    private static PropertyInfo? TryGetPropertyFromMethod(MethodInfo method)
+    {
+        var type = method.DeclaringType;
+        return type?.GetRuntimeProperties().FirstOrDefault(prop => prop.GetMethod == method);
+    }
+
+    private class TypeResolver
+    {
+        private Dictionary<string, Type> _registered = new();
+        public void Add(string name, Type type) => _registered.Add(name, type);
+        public Type Resolve(string? ns, string name)
+        {
+            if (_registered.TryGetValue(name, out var type))
+                return type;
+            throw new Exception($"Unable to resolve type '{name}'.");
+        }
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/CompiledBindingPathFromExpressionBuilder.cs b/tests/Avalonia.Base.UnitTests/Data/Core/CompiledBindingPathFromExpressionBuilder.cs
new file mode 100644
index 000000000..0662fd94b
--- /dev/null
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/CompiledBindingPathFromExpressionBuilder.cs
@@ -0,0 +1,314 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+using System.Linq.Expressions;
+using System.Reflection;
+using System.Threading.Tasks;
+using Avalonia.Data.Core;
+using Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings;
+
+#nullable enable
+
+namespace Avalonia.Base.UnitTests.Data.Core;
+
+internal class CompiledBindingPathFromExpressionBuilder : ExpressionVisitor
+{
+    private static readonly PropertyInfo AvaloniaObjectIndexer;
+    private static readonly MethodInfo CreateDelegateMethod;
+    private static readonly string IndexerGetterName = "get_Item";
+    private const string MultiDimensionalArrayGetterMethodName = "Get";
+    private readonly bool _enableDataValidation;
+    private readonly LambdaExpression _rootExpression;
+    private readonly CompiledBindingPathBuilder _builder = new();
+    private Expression? _head;
+
+    public CompiledBindingPathFromExpressionBuilder(LambdaExpression expression, bool enableDataValidation)
+    {
+        _rootExpression = expression;
+        _enableDataValidation = enableDataValidation;
+    }
+
+    static CompiledBindingPathFromExpressionBuilder()
+    {
+        AvaloniaObjectIndexer = typeof(AvaloniaObject).GetProperty("Item", new[] { typeof(AvaloniaProperty) })!;
+        CreateDelegateMethod = typeof(MethodInfo).GetMethod("CreateDelegate", new[] { typeof(Type), typeof(object) })!;
+    }
+
+    public static CompiledBindingPath Build<TIn, TOut>(Expression<Func<TIn, TOut>> expression, bool enableDataValidation)
+    {
+        var visitor = new CompiledBindingPathFromExpressionBuilder(expression, enableDataValidation);
+        visitor.Visit(expression);
+        return visitor._builder.Build();
+    }
+
+    protected override Expression VisitBinary(BinaryExpression node)
+    {
+        // Indexers require more work since the compiler doesn't generate IndexExpressions:
+        // they weren't in System.Linq.Expressions v1 and so must be generated manually.
+        if (node.NodeType == ExpressionType.ArrayIndex)
+            return Visit(Expression.MakeIndex(node.Left, null, new[] { node.Right }));
+
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitIndex(IndexExpression node)
+    {
+        if (node.Indexer == AvaloniaObjectIndexer)
+        {
+            var property = GetValue<AvaloniaProperty>(node.Arguments[0]);
+            return Add(node.Object, node, x => x.Property(property, PropertyInfoAccessorFactory.CreateAvaloniaPropertyAccessor));
+        }
+        else if (node.Object?.Type.IsArray == true)
+        {
+            var indexes = node.Arguments.Select(GetValue<int>).ToArray();
+            return Add(node.Object, node, x => x.ArrayElement(indexes, node.Type));
+        }
+        else if (node.Indexer?.GetMethod is not null && 
+            node.Arguments.Count == 1 &&
+            node.Arguments[0].Type == typeof(int))
+        {
+            var getMethod = node.Indexer.GetMethod;
+            var setMethod = node.Indexer.SetMethod;
+            var index = GetValue<int>(node.Arguments[0]);
+            var info = new ClrPropertyInfo(
+                CommonPropertyNames.IndexerName,
+                x => getMethod.Invoke(x, new object[] { index }),
+                setMethod is not null ? (o, v) => setMethod.Invoke(o, new[] { v }) : null,
+                getMethod.ReturnType);
+            return Add(node.Object, node, x => x.Property(
+                info, 
+                (x, i) => PropertyInfoAccessorFactory.CreateIndexerPropertyAccessor(x, i, index)));
+        }
+        else if (node.Indexer?.GetMethod is not null)
+        {
+            var getMethod = node.Indexer.GetMethod;
+            var setMethod = node.Indexer?.SetMethod;
+            var indexes = node.Arguments.Select(GetValue<object>).ToArray();
+            var info = new ClrPropertyInfo(
+                CommonPropertyNames.IndexerName,
+                x => getMethod.Invoke(x, indexes),
+                setMethod is not null ? (o, v) => setMethod.Invoke(o, indexes.Append(v).ToArray()) : null,
+                getMethod.ReturnType);
+            return Add(node.Object, node, x => x.Property(
+                info,
+                PropertyInfoAccessorFactory.CreateInpcPropertyAccessor));
+        }
+
+        throw new ExpressionParseException(0, $"Invalid indexer in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitMember(MemberExpression node)
+    {
+        if (node.Member.MemberType != MemberTypes.Property)
+            throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+
+        if (typeof(AvaloniaObject).IsAssignableFrom(node.Expression?.Type) &&
+            AvaloniaPropertyRegistry.Instance.FindRegistered(node.Expression.Type, node.Member.Name) is { } avaloniaProperty)
+        {
+            return Add(
+                node.Expression, 
+                node, 
+                x => x.Property(avaloniaProperty, PropertyInfoAccessorFactory.CreateAvaloniaPropertyAccessor));
+        }
+        else
+        {
+            var property = (PropertyInfo)node.Member;
+            var info = new ClrPropertyInfo(
+                property.Name,
+                CreateGetter(property),
+                CreateSetter(property),
+                property.PropertyType);
+            return Add(node.Expression, node, x => x.Property(info, PropertyInfoAccessorFactory.CreateInpcPropertyAccessor));
+        }
+    }
+
+    protected override Expression VisitMethodCall(MethodCallExpression node)
+    {
+        var method = node.Method;
+
+        if (method.Name == IndexerGetterName && node.Object is not null)
+        {
+            var property = TryGetPropertyFromMethod(method);
+            return Visit(Expression.MakeIndex(node.Object, property, node.Arguments));
+        }
+        else if (method.Name == MultiDimensionalArrayGetterMethodName &&
+                 node.Object is not null)
+        {
+            var indexes = node.Arguments.Select(GetValue<int>).ToArray();
+            return Add(node.Object, node, x => x.ArrayElement(indexes, node.Type));
+        }
+        else if (method.Name.StartsWith(StreamBindingExtensions.StreamBindingName) &&
+                 method.DeclaringType == typeof(StreamBindingExtensions) &&
+                 method.GetGenericArguments() is [Type genericArg])
+        {
+            var instance = node.Method.IsStatic ? node.Arguments[0] : node.Object;
+
+            if (typeof(Task<>).MakeGenericType(genericArg).IsAssignableFrom(instance?.Type))
+            {
+                var builderMethod = typeof(CompiledBindingPathBuilder)
+                    .GetMethod(nameof(CompiledBindingPathBuilder.StreamTask))!
+                    .MakeGenericMethod(genericArg);
+                return Add(instance, node, x => builderMethod.Invoke(x, null));
+            }
+            else if (typeof(IObservable<>).MakeGenericType(genericArg).IsAssignableFrom(instance?.Type))
+            {
+                var builderMethod = typeof(CompiledBindingPathBuilder)
+                    .GetMethod(nameof(CompiledBindingPathBuilder.StreamObservable))!
+                    .MakeGenericMethod(genericArg);
+                return Add(instance, node, x => builderMethod.Invoke(x, null));
+            }
+        }
+
+        throw new ExpressionParseException(0, $"Invalid method call in binding expression: '{node.Method.DeclaringType}.{node.Method.Name}'.");
+    }
+
+    protected override Expression VisitParameter(ParameterExpression node)
+    {
+        if (node == _rootExpression.Parameters[0] && _head is null)
+            _head = node;
+        return base.VisitParameter(node);
+    }
+
+    protected override Expression VisitUnary(UnaryExpression node)
+    {
+        if (node.NodeType == ExpressionType.Not && node.Type == typeof(bool))
+        {
+            return Add(node.Operand, node, x => x.Not());
+        }
+        else if (node.NodeType == ExpressionType.Convert)
+        {
+            if (node.Operand.Type.IsAssignableFrom(node.Type))
+            {
+                // Ignore inheritance casts 
+                return _head = base.VisitUnary(node);
+            }
+        }
+        else if (node.NodeType == ExpressionType.TypeAs)
+        {
+            // Ignore as operator.
+            return _head = base.VisitUnary(node);
+        }
+
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitBlock(BlockExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override CatchBlock VisitCatchBlock(CatchBlock node)
+    {
+        throw new ExpressionParseException(0, $"Catch blocks are not allowed in binding expressions.");
+    }
+
+    protected override Expression VisitConditional(ConditionalExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitDynamic(DynamicExpression node)
+    {
+        throw new ExpressionParseException(0, $"Dynamic expressions are not allowed in binding expressions.");
+    }
+
+    protected override ElementInit VisitElementInit(ElementInit node)
+    {
+        throw new ExpressionParseException(0, $"Element init expressions are not valid in a binding expression.");
+    }
+
+    protected override Expression VisitGoto(GotoExpression node)
+    {
+        throw new ExpressionParseException(0, $"Goto expressions not supported in binding expressions.");
+    }
+
+    protected override Expression VisitInvocation(InvocationExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitLabel(LabelExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitListInit(ListInitExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitLoop(LoopExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override MemberAssignment VisitMemberAssignment(MemberAssignment node)
+    {
+        throw new ExpressionParseException(0, $"Member assignments not supported in binding expressions.");
+    }
+
+    protected override Expression VisitSwitch(SwitchExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitTry(TryExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    protected override Expression VisitTypeBinary(TypeBinaryExpression node)
+    {
+        throw new ExpressionParseException(0, $"Invalid expression type in binding expression: {node.NodeType}.");
+    }
+
+    private Expression Add(Expression? instance, Expression expression, Action<CompiledBindingPathBuilder> build)
+    {
+        var visited = Visit(instance);
+        if (visited != _head)
+            throw new ExpressionParseException(
+                0,
+                $"Unable to parse '{expression}': expected an instance of '{_head}' but got '{visited}'.");
+        build(_builder);
+        return _head = expression;
+    }
+
+    private static Func<object, object>? CreateGetter(PropertyInfo info)
+    {
+        if (info.GetMethod == null)
+            return null;
+        var target = Expression.Parameter(typeof(object), "target");
+        return Expression.Lambda<Func<object, object>>(
+                Expression.Convert(Expression.Call(Expression.Convert(target, info.DeclaringType!), info.GetMethod),
+                    typeof(object)),
+                target)
+            .Compile();
+    }
+
+    private static Action<object, object?>? CreateSetter(PropertyInfo info)
+    {
+        if (info.SetMethod == null)
+            return null;
+        var target = Expression.Parameter(typeof(object), "target");
+        var value = Expression.Parameter(typeof(object), "value");
+        return Expression.Lambda<Action<object, object?>>(
+                Expression.Call(Expression.Convert(target, info.DeclaringType!), info.SetMethod,
+                    Expression.Convert(value, info.SetMethod.GetParameters()[0].ParameterType)),
+                target, value)
+            .Compile();
+    }
+
+    private static T GetValue<T>(Expression expr)
+    {
+        if (expr is ConstantExpression constant)
+            return (T)constant.Value!;
+        return Expression.Lambda<Func<T>>(expr).Compile(preferInterpretation: true)();
+    }
+
+    private static PropertyInfo? TryGetPropertyFromMethod(MethodInfo method)
+    {
+        var type = method.DeclaringType;
+        return type?.GetRuntimeProperties().FirstOrDefault(prop => prop.GetMethod == method);
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_AttachedProperty.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_AttachedProperty.cs
deleted file mode 100644
index c04e726a8..000000000
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_AttachedProperty.cs
+++ /dev/null
@@ -1,125 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Reactive.Linq;
-using System.Threading.Tasks;
-using Avalonia.Diagnostics;
-using Avalonia.Data.Core;
-using Xunit;
-
-namespace Avalonia.Base.UnitTests.Data.Core
-{
-    public class ExpressionObserverTests_AttachedProperty
-    {
-
-        [Fact]
-        public async Task Should_Get_Attached_Property_Value()
-        {
-            var data = new Class1();
-            var target = ExpressionObserver.Create(data, o => o[Owner.FooProperty]);
-            var result = await target.Take(1);
-
-            Assert.Equal("foo", result);
-
-            Assert.Null(((IAvaloniaObjectDebug)data).GetPropertyChangedSubscribers());
-        }
-
-        [Fact]
-        public async Task Should_Get_Chained_Attached_Property_Value()
-        {
-            var data = new Class1
-            {
-                Next = new Class1
-                {
-                    [Owner.FooProperty] = "bar",
-                }
-            };
-
-            var target = ExpressionObserver.Create(data, o => o.Next[Owner.FooProperty]);
-            var result = await target.Take(1);
-
-            Assert.Equal("bar", result);
-
-            Assert.Null(((IAvaloniaObjectDebug)data).GetPropertyChangedSubscribers());
-        }
-
-        [Fact]
-        public void Should_Track_Simple_Attached_Value()
-        {
-            var data = new Class1();
-            var target = ExpressionObserver.Create(data, o => o[Owner.FooProperty]);
-            var result = new List<object>();
-
-            var sub = target.Subscribe(x => result.Add(x));
-            data.SetValue(Owner.FooProperty, "bar");
-
-            Assert.Equal(new[] { "foo", "bar" }, result);
-
-            sub.Dispose();
-
-            Assert.Null(((IAvaloniaObjectDebug)data).GetPropertyChangedSubscribers());
-        }
-
-        [Fact]
-        public void Should_Track_Chained_Attached_Value()
-        {
-            var data = new Class1
-            {
-                Next = new Class1
-                {
-                    [Owner.FooProperty] = "foo",
-                }
-            };
-
-            var target = ExpressionObserver.Create(data, o => o.Next[Owner.FooProperty]);
-            var result = new List<object>();
-
-            var sub = target.Subscribe(x => result.Add(x));
-            data.Next.SetValue(Owner.FooProperty, "bar");
-
-            Assert.Equal(new[] { "foo", "bar" }, result);
-
-            sub.Dispose();
-
-            Assert.Null(((IAvaloniaObjectDebug)data).GetPropertyChangedSubscribers());
-        }
-
-        [Fact]
-        public void Should_Not_Keep_Source_Alive()
-        {
-            Func<Tuple<ExpressionObserver, WeakReference>> run = () =>
-            {
-                var source = new Class1();
-                var target = ExpressionObserver.Create(source, o => o.Next[Owner.FooProperty]);
-                return Tuple.Create(target, new WeakReference(source));
-            };
-
-            var result = run();
-            result.Item1.Subscribe(x => { });
-
-            GC.Collect();
-
-            Assert.Null(result.Item2.Target);
-        }
-
-        private static class Owner
-        {
-            public static readonly AttachedProperty<string> FooProperty =
-                AvaloniaProperty.RegisterAttached<Class1, string>(
-                    "Foo", 
-                    typeof(Owner), 
-                    defaultValue: "foo");
-        }
-
-        private class Class1 : AvaloniaObject
-        {
-            public static readonly StyledProperty<Class1> NextProperty =
-                AvaloniaProperty.Register<Class1, Class1>(nameof(Next));
-
-            public Class1 Next
-            {
-                get { return GetValue(NextProperty); }
-                set { SetValue(NextProperty, value); }
-            }
-        }
-    }
-}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_AvaloniaProperty.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_AvaloniaProperty.cs
deleted file mode 100644
index 650e5d60e..000000000
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_AvaloniaProperty.cs
+++ /dev/null
@@ -1,86 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Reactive.Linq;
-using System.Threading.Tasks;
-using Avalonia.Diagnostics;
-using Avalonia.Data.Core;
-using Xunit;
-using Avalonia.Markup.Parsers;
-
-namespace Avalonia.Base.UnitTests.Data.Core
-{
-    public class ExpressionObserverTests_AvaloniaProperty
-    {
-        public ExpressionObserverTests_AvaloniaProperty()
-        {
-            var foo = Class1.FooProperty;
-        }
-
-        [Fact]
-        public async Task Should_Get_Simple_Property_Value()
-        {
-            var data = new Class1();
-            var target = ExpressionObserver.Create(data, o => o.Foo);
-            var result = await target.Take(1);
-
-            Assert.Equal("foo", result);
-
-            Assert.Null(((IAvaloniaObjectDebug)data).GetPropertyChangedSubscribers());
-        }
-
-        [Fact]
-        public async Task Should_Get_Simple_ClrProperty_Value()
-        {
-            var data = new Class1();
-            var target = ExpressionObserver.Create(data, o => o.ClrProperty);
-            var result = await target.Take(1);
-
-            Assert.Equal("clr-property", result);
-        }
-
-        [Fact]
-        public void Should_Track_Simple_Property_Value()
-        {
-            var data = new Class1();
-            var target = ExpressionObserver.Create(data, o => o.Foo);
-            var result = new List<object>();
-
-            var sub = target.Subscribe(x => result.Add(x));
-            data.SetValue(Class1.FooProperty, "bar");
-
-            Assert.Equal(new[] { "foo", "bar" }, result);
-
-            sub.Dispose();
-
-            Assert.Null(((IAvaloniaObjectDebug)data).GetPropertyChangedSubscribers());
-        }
-
-        [Fact]
-        public void Should_Not_Keep_Source_Alive()
-        {
-            Func<Tuple<ExpressionObserver, WeakReference>> run = () =>
-            {
-                var source = new Class1();
-                var target = ExpressionObserver.Create(source, o => o.Foo);
-                return Tuple.Create(target, new WeakReference(source));
-            };
-
-            var result = run();
-            result.Item1.Subscribe(x => { });
-
-            GC.Collect();
-
-            Assert.Null(result.Item2.Target);
-        }
-
-        private class Class1 : AvaloniaObject
-        {
-            public static readonly StyledProperty<string> FooProperty =
-                AvaloniaProperty.Register<Class1, string>("Foo", defaultValue: "foo");
-
-            public string Foo { get => GetValue(FooProperty); set => SetValue(FooProperty, value); }
-
-            public string ClrProperty { get; } = "clr-property";
-        }
-    }
-}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_DataValidation.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_DataValidation.cs
deleted file mode 100644
index d1417ea76..000000000
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_DataValidation.cs
+++ /dev/null
@@ -1,227 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using Avalonia.Data;
-using Avalonia.Data.Core;
-using Avalonia.Threading;
-using Avalonia.UnitTests;
-using Xunit;
-
-namespace Avalonia.Base.UnitTests.Data.Core
-{
-    [InvariantCulture]
-    public class ExpressionObserverTests_DataValidation
-    {
-        ////[Fact]
-        ////public void Doesnt_Send_DataValidationError_When_DataValidatation_Not_Enabled()
-        ////{
-        ////    var data = new ExceptionTest { MustBePositive = 5 };
-        ////    var observer = ExpressionObserver.Create(data, o => o.MustBePositive, false);
-        ////    var validationMessageFound = false;
-
-        ////    observer.OfType<BindingNotification>()
-        ////        .Where(x => x.ErrorType == BindingErrorType.DataValidationError)
-        ////        .Subscribe(_ => validationMessageFound = true);
-        ////    observer.SetValue(-5);
-
-        ////    Assert.False(validationMessageFound);
-
-        ////    GC.KeepAlive(data);
-        ////}
-
-        ////[Fact]
-        ////public void Exception_Validation_Sends_DataValidationError()
-        ////{
-        ////    var data = new ExceptionTest { MustBePositive = 5 };
-        ////    var observer = ExpressionObserver.Create(data, o => o.MustBePositive, true);
-        ////    var validationMessageFound = false;
-
-        ////    observer.OfType<BindingNotification>()
-        ////        .Where(x => x.ErrorType == BindingErrorType.DataValidationError)
-        ////        .Subscribe(_ => validationMessageFound = true);
-        ////    observer.SetValue(-5);
-
-        ////    Assert.True(validationMessageFound);
-
-        ////    GC.KeepAlive(data);
-        ////}
-
-        [Fact]
-        public void Indei_Validation_Does_Not_Subscribe_When_DataValidation_Not_Enabled()
-        {
-            var data = new IndeiTest { MustBePositive = 5 };
-            var observer = ExpressionObserver.Create(data, o => o.MustBePositive, false);
-
-            observer.Subscribe(_ => { });
-
-            Assert.Equal(0, data.ErrorsChangedSubscriptionCount);
-        }
-
-        [Fact]
-        public void Enabled_Indei_Validation_Subscribes()
-        {
-            var data = new IndeiTest { MustBePositive = 5 };
-            var observer = ExpressionObserver.Create(data, o => o.MustBePositive, true);
-            var sub = observer.Subscribe(_ => { });
-
-            Assert.Equal(1, data.ErrorsChangedSubscriptionCount);
-            sub.Dispose();
-            // Forces WeakEvent compact
-            Dispatcher.UIThread.RunJobs();
-            Assert.Equal(0, data.ErrorsChangedSubscriptionCount);
-        }
-
-        [Fact]
-        public void Validation_Plugins_Send_Correct_Notifications()
-        {
-            var data = new IndeiTest();
-            var observer = ExpressionObserver.Create(data, o => o.MustBePositive, true);
-            var result = new List<object>();
-            
-            var errmsg = string.Empty;
-            try { typeof(IndeiTest).GetProperty(nameof(IndeiTest.MustBePositive)).SetValue(data, "foo"); }
-            catch(Exception e) { errmsg = e.Message; }
-
-            observer.Subscribe(x => result.Add(x));
-            observer.SetValue(5);
-            observer.SetValue(-5);
-            observer.SetValue("foo");
-            observer.SetValue(5);
-
-            Assert.Equal(new[]
-            {
-                new BindingNotification(0),
-
-                // Value is notified twice as ErrorsChanged is always called by IndeiTest.
-                new BindingNotification(5),
-                new BindingNotification(5),
-
-                // Value is first signalled without an error as validation hasn't been updated.
-                new BindingNotification(-5),
-                new BindingNotification(new DataValidationException("Must be positive"), BindingErrorType.DataValidationError, -5),
-
-                // Exception is thrown by trying to set value to "foo".
-                new BindingNotification(
-                    new ArgumentException(errmsg),
-                    BindingErrorType.DataValidationError),
-
-                // Value is set then validation is updated.
-                new BindingNotification(new DataValidationException("Must be positive"), BindingErrorType.DataValidationError, 5),
-                new BindingNotification(5),
-            }, result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Doesnt_Subscribe_To_Indei_Of_Intermediate_Object_In_Chain()
-        {
-            var data = new Container
-            {
-                Inner = new IndeiTest()
-            };
-
-            var observer = ExpressionObserver.Create(data, o => o.Inner.MustBePositive, true);
-
-            observer.Subscribe(_ => { });
-
-            // We may want to change this but I've never seen an example of data validation on an
-            // intermediate object in a chain so for the moment I'm not sure what the result of 
-            // validating such a thing should look like.
-            Assert.Equal(0, data.ErrorsChangedSubscriptionCount);
-            Assert.Equal(1, data.Inner.ErrorsChangedSubscriptionCount);
-        }
-
-        [Fact]
-        public void Sends_Correct_Notifications_With_Property_Chain()
-        {
-            var container = new Container();
-
-            var observer = ExpressionObserver.Create(container, o => o.Inner.MustBePositive, true);
-
-            var result = new List<object>();
-
-            observer.Subscribe(x => result.Add(x));
-
-            Assert.Equal(new[]
-            {
-                new BindingNotification(
-                    new MarkupBindingChainException("Null value", "o => o.Inner.MustBePositive", "Inner"),
-                    BindingErrorType.Error,
-                    AvaloniaProperty.UnsetValue),
-            }, result);
-
-            GC.KeepAlive(container);
-        }
-
-        public class ExceptionTest : NotifyingBase
-        {
-            private int _mustBePositive;
-
-            public int MustBePositive
-            {
-                get { return _mustBePositive; }
-                set
-                {
-                    if (value <= 0)
-                    {
-                        throw new ArgumentOutOfRangeException(nameof(value));
-                    }
-
-                    _mustBePositive = value;
-                    RaisePropertyChanged();
-                }
-            }
-        }
-
-        private class IndeiTest : IndeiBase
-        {
-            private int _mustBePositive;
-            private Dictionary<string, IList<string>> _errors = new Dictionary<string, IList<string>>();
-
-            public int MustBePositive
-            {
-                get { return _mustBePositive; }
-                set
-                {
-                    _mustBePositive = value;
-                    RaisePropertyChanged();
-
-                    if (value >= 0)
-                    {
-                        _errors.Remove(nameof(MustBePositive));
-                        RaiseErrorsChanged(nameof(MustBePositive));
-                    }
-                    else
-                    {
-                        _errors[nameof(MustBePositive)] = new[] { "Must be positive" };
-                        RaiseErrorsChanged(nameof(MustBePositive));
-                    }
-                }
-            }
-
-            public override bool HasErrors => _mustBePositive >= 0;
-
-            public override IEnumerable GetErrors(string propertyName)
-            {
-                IList<string> result;
-                _errors.TryGetValue(propertyName, out result);
-                return result;
-            }
-        }
-
-        private class Container : IndeiBase
-        {
-            private IndeiTest _inner;
-
-            public IndeiTest Inner
-            {
-                get { return _inner; }
-                set { _inner = value; RaisePropertyChanged(); }
-            }
-
-            public override bool HasErrors => false;
-            public override IEnumerable GetErrors(string propertyName) => null;
-        }
-    }
-}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_ExpressionTree.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_ExpressionTree.cs
deleted file mode 100644
index 6cd757331..000000000
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_ExpressionTree.cs
+++ /dev/null
@@ -1,224 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Reactive.Linq;
-using System.Text;
-using System.Threading.Tasks;
-using Avalonia.Data.Core;
-using Avalonia.UnitTests;
-using Xunit;
-
-namespace Avalonia.Base.UnitTests.Data.Core
-{
-    public class ExpressionObserverTests_ExpressionTree
-    {
-        [Fact]
-        public async Task IdentityExpression_Creates_IdentityObserver()
-        {
-            var target = new object();
-
-            var observer = ExpressionObserver.Create(target, o => o);
-
-            Assert.Equal(target, await observer.Take(1));
-            GC.KeepAlive(target);
-        }
-
-        [Fact]
-        public async Task Property_Access_Expression_Observes_Property()
-        {
-            var target = new Class1();
-
-            var observer = ExpressionObserver.Create(target, o => o.Foo);
-
-            Assert.Null(await observer.Take(1));
-
-            using (observer.Subscribe(_ => {}))
-            {
-                target.Foo = "Test"; 
-            }
-
-            Assert.Equal("Test", await observer.Take(1));
-
-            GC.KeepAlive(target);
-        }
-
-        [Fact]
-        public void Property_Access_Expression_Can_Set_Property()
-        {
-            var data = new Class1();
-            var target = ExpressionObserver.Create(data, o => o.Foo);
-
-            using (target.Subscribe(_ => { }))
-            {
-                Assert.True(target.SetValue("baz"));
-            }
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public async Task Indexer_Accessor_Can_Read_Value()
-        {
-            var data = new[] { 1, 2, 3, 4 };
-
-            var target = ExpressionObserver.Create(data, o => o[0]);
-
-            Assert.Equal(data[0], await target.Take(1));
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public async Task Indexer_List_Accessor_Can_Read_Value()
-        {
-            var data = new List<int> { 1, 2, 3, 4 };
-
-            var target = ExpressionObserver.Create(data, o => o[0]);
-
-            Assert.Equal(data[0], await target.Take(1));
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public async Task Indexer_Accessor_Can_Read_Complex_Index()
-        {
-            var data = new Dictionary<object, object>();
-
-            var key = new object();
-
-            data.Add(key, new object());
-
-            var target = ExpressionObserver.Create(data, o => o[key]);
-
-            Assert.Equal(data[key], await target.Take(1));
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Indexer_Can_Set_Value()
-        {
-            var data = new[] { 1, 2, 3, 4 };
-
-            var target = ExpressionObserver.Create(data, o => o[0]);
-
-            using (target.Subscribe(_ => { }))
-            {
-                Assert.True(target.SetValue(2));
-            }
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public async Task Inheritance_Casts_Should_Be_Ignored()
-        {
-            NotifyingBase test = new Class1 { Foo = "Test" };
-
-            var target = ExpressionObserver.Create(test, o => ((Class1)o).Foo);
-
-            Assert.Equal("Test", await target.Take(1));
-
-            GC.KeepAlive(test);
-        }
-
-        [Fact]
-        public void Convert_Casts_Should_Error()
-        {
-            var test = 1;
-
-            Assert.Throws<ExpressionParseException>(() => ExpressionObserver.Create(test, o => (double)o));
-        }
-
-        [Fact]
-        public async Task As_Operator_Should_Be_Ignored()
-        {
-            NotifyingBase test = new Class1 { Foo = "Test" };
-
-            var target = ExpressionObserver.Create(test, o => (o as Class1).Foo);
-
-            Assert.Equal("Test", await target.Take(1));
-
-            GC.KeepAlive(test);
-        }
-
-        [Fact]
-        public async Task Avalonia_Property_Indexer_Reads_Avalonia_Property_Value()
-        {
-            var test = new Class2();
-
-            var target = ExpressionObserver.Create(test, o => o[Class2.FooProperty]);
-
-            Assert.Equal("foo", await target.Take(1));
-
-            GC.KeepAlive(test);
-        }
-
-        [Fact]
-        public async Task Complex_Expression_Correctly_Parsed()
-        {
-            var test = new Class1 { Foo = "Test" };
-
-            var target = ExpressionObserver.Create(test, o => o.Foo.Length);
-
-            Assert.Equal(test.Foo.Length, await target.Take(1));
-
-            GC.KeepAlive(test);
-        }
-
-        [Fact]
-        public void Should_Get_Completed_Task_Value()
-        {
-            using (var sync = UnitTestSynchronizationContext.Begin())
-            {
-                var data = new { Foo = Task.FromResult("foo") };
-                var target = ExpressionObserver.Create(data, o => o.Foo.StreamBinding());
-                var result = new List<object>();
-
-                var sub = target.Subscribe(x => result.Add(x));
-
-                Assert.Equal(new[] { "foo" }, result);
-
-                GC.KeepAlive(data);
-            }
-        }
-
-        [Fact]
-        public async Task Should_Create_Method_Binding()
-        {
-            var data = new Class3();
-            var target = ExpressionObserver.Create(data, o => (Action)o.Method);
-            var value = await target.Take(1);
-
-            Assert.IsAssignableFrom<Delegate>(value);
-            GC.KeepAlive(data);
-        }
-
-        private class Class1 : NotifyingBase
-        {
-            private string _foo;
-
-            public string Foo
-            {
-                get { return _foo; }
-                set
-                {
-                    _foo = value;
-                    RaisePropertyChanged(nameof(Foo));
-                }
-            }
-        }
-
-
-        private class Class2 : AvaloniaObject
-        {
-            public static readonly StyledProperty<string> FooProperty =
-                AvaloniaProperty.Register<Class2, string>("Foo", defaultValue: "foo");
-
-            public string ClrProperty { get; } = "clr-property";
-        }
-
-        private class Class3
-        {
-            public void Method() { }
-        }
-    }
-}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Indexer.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Indexer.cs
deleted file mode 100644
index 20a4cb6d9..000000000
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Indexer.cs
+++ /dev/null
@@ -1,333 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Collections.ObjectModel;
-using System.Reactive.Linq;
-using System.Threading.Tasks;
-using Avalonia.Collections;
-using Avalonia.Diagnostics;
-using Avalonia.Data.Core;
-using Avalonia.UnitTests;
-using Xunit;
-using Avalonia.Markup.Parsers;
-using Avalonia.Threading;
-
-namespace Avalonia.Base.UnitTests.Data.Core
-{
-    public class ExpressionObserverTests_Indexer
-    {
-        [Fact]
-        public async Task Should_Get_Array_Value()
-        {
-            var data = new { Foo = new [] { "foo", "bar" } };
-            var target = ExpressionObserver.Create(data, x => x.Foo[1]);
-            var result = await target.Take(1);
-
-            Assert.Equal("bar", result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public async Task Should_Get_MultiDimensional_Array_Value()
-        {
-            var data = new { Foo = new[,] { { "foo", "bar" }, { "baz", "qux" } } };
-            var target = ExpressionObserver.Create(data, o => o.Foo[1, 1]);
-            var result = await target.Take(1);
-
-            Assert.Equal("qux", result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public async Task Should_Get_Value_For_String_Indexer()
-        {
-            var data = new { Foo = new Dictionary<string, string> { { "foo", "bar" }, { "baz", "qux" } } };
-            var target = ExpressionObserver.Create(data, o => o.Foo["foo"]);
-            var result = await target.Take(1);
-
-            Assert.Equal("bar", result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public async Task Should_Get_Value_For_Non_String_Indexer()
-        {
-            var data = new { Foo = new Dictionary<double, string> { { 1.0, "bar" }, { 2.0, "qux" } } };
-            var target = ExpressionObserver.Create(data, o => o.Foo[1.0]);
-            var result = await target.Take(1);
-
-            Assert.Equal("bar", result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public async Task Array_Out_Of_Bounds_Should_Return_UnsetValue()
-        {
-            var data = new { Foo = new[] { "foo", "bar" } };
-            var target = ExpressionObserver.Create(data, o => o.Foo[2]);
-            var result = await target.Take(1);
-
-            Assert.Equal(AvaloniaProperty.UnsetValue, result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public async Task List_Out_Of_Bounds_Should_Return_UnsetValue()
-        {
-            var data = new { Foo = new List<string> { "foo", "bar" } };
-            var target = ExpressionObserver.Create(data, o => o.Foo[2]);
-            var result = await target.Take(1);
-
-            Assert.Equal(AvaloniaProperty.UnsetValue, result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public async Task Should_Get_List_Value()
-        {
-            var data = new { Foo = new List<string> { "foo", "bar" } };
-            var target = ExpressionObserver.Create(data, o => o.Foo[1]);
-            var result = await target.Take(1);
-
-            Assert.Equal("bar", result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Track_INCC_Add()
-        {
-            var data = new { Foo = new AvaloniaList<string> { "foo", "bar" } };
-            var target = ExpressionObserver.Create(data, o => o.Foo[2]);
-            var result = new List<object>();
-
-            using (var sub = target.Subscribe(x => result.Add(x)))
-            {
-                data.Foo.Add("baz");
-            }
-
-            // Forces WeakEvent compact
-            Dispatcher.UIThread.RunJobs();
-            
-            Assert.Equal(new[] { AvaloniaProperty.UnsetValue, "baz" }, result);
-            Assert.Null(((INotifyCollectionChangedDebug)data.Foo).GetCollectionChangedSubscribers());
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Track_INCC_Remove()
-        {
-            var data = new { Foo = new AvaloniaList<string> { "foo", "bar" } };
-            var target = ExpressionObserver.Create(data, o => o.Foo[0]);
-            var result = new List<object>();
-
-            using (var sub = target.Subscribe(x => result.Add(x)))
-            {
-                data.Foo.RemoveAt(0);
-            }
-            // Forces WeakEvent compact
-            Dispatcher.UIThread.RunJobs();
-
-            Assert.Equal(new[] { "foo", "bar" }, result);
-            Assert.Null(((INotifyCollectionChangedDebug)data.Foo).GetCollectionChangedSubscribers());
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Track_INCC_Replace()
-        {
-            var data = new { Foo = new AvaloniaList<string> { "foo", "bar" } };
-            var target = ExpressionObserver.Create(data, o => o.Foo[1]);
-            var result = new List<object>();
-
-            using (var sub = target.Subscribe(x => result.Add(x)))
-            {
-                data.Foo[1] = "baz";
-            }
-            
-            // Forces WeakEvent compact
-            Dispatcher.UIThread.RunJobs();
-
-            Assert.Equal(new[] { "bar", "baz" }, result);
-            Assert.Null(((INotifyCollectionChangedDebug)data.Foo).GetCollectionChangedSubscribers());
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Track_INCC_Move()
-        {
-            // Using ObservableCollection here because AvaloniaList does not yet have a Move
-            // method, but even if it did we need to test with ObservableCollection as well
-            // as AvaloniaList as it implements PropertyChanged as an explicit interface event.
-            var data = new { Foo = new ObservableCollection<string> { "foo", "bar" } };
-            var target = ExpressionObserver.Create(data, o => o.Foo[1]);
-            var result = new List<object>();
-
-            var sub = target.Subscribe(x => result.Add(x));
-            data.Foo.Move(0, 1);
-
-            Assert.Equal(new[] { "bar", "foo" }, result);
-
-            GC.KeepAlive(sub);
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Track_INCC_Reset()
-        {
-            var data = new { Foo = new AvaloniaList<string> { "foo", "bar" } };
-            var target = ExpressionObserver.Create(data, o => o.Foo[1]);
-            var result = new List<object>();
-
-            var sub = target.Subscribe(x => result.Add(x));
-            data.Foo.Clear();
-
-            Assert.Equal(new[] { "bar", AvaloniaProperty.UnsetValue }, result);
-
-            GC.KeepAlive(sub);
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Track_NonIntegerIndexer()
-        {
-            var data = new { Foo = new NonIntegerIndexer() };
-            data.Foo["foo"] = "bar";
-            data.Foo["baz"] = "qux";
-
-            var target = ExpressionObserver.Create(data, o => o.Foo["foo"]);
-            var result = new List<object>();
-
-            using (var sub = target.Subscribe(x => result.Add(x)))
-            {
-                data.Foo["foo"] = "bar2";
-            }
-
-            // Forces WeakEvent compact
-            Dispatcher.UIThread.RunJobs();
-            
-            var expected = new[] { "bar", "bar2" };
-            Assert.Equal(expected, result);
-            Assert.Equal(0, data.Foo.PropertyChangedSubscriptionCount);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_SetArrayIndex()
-        {
-            var data = new { Foo = new[] { "foo", "bar" } };
-            var target = ExpressionObserver.Create(data, o => o.Foo[1]);
-
-            using (target.Subscribe(_ => { }))
-            {
-                Assert.True(target.SetValue("baz"));
-            }
-
-            Assert.Equal("baz", data.Foo[1]);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Set_ExistingDictionaryEntry()
-        {
-            var data = new
-            {
-                Foo = new Dictionary<string, int>
-                {
-                    {"foo", 1 }
-                }
-            };
-
-            var target = ExpressionObserver.Create(data, o => o.Foo["foo"]);
-            using (target.Subscribe(_ => { }))
-            {
-                Assert.True(target.SetValue(4));
-            }
-
-            Assert.Equal(4, data.Foo["foo"]);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Add_NewDictionaryEntry()
-        {
-            var data = new
-            {
-                Foo = new Dictionary<string, int>
-                {
-                    {"foo", 1 }
-                }
-            };
-
-            var target = ExpressionObserver.Create(data, o => o.Foo["bar"]);
-            using (target.Subscribe(_ => { }))
-            {
-                Assert.True(target.SetValue(4));
-            }
-
-            Assert.Equal(4, data.Foo["bar"]);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Set_NonIntegerIndexer()
-        {
-            var data = new { Foo = new NonIntegerIndexer() };
-            data.Foo["foo"] = "bar";
-            data.Foo["baz"] = "qux";
-
-            var target = ExpressionObserver.Create(data, o => o.Foo["foo"]);
-
-            using (target.Subscribe(_ => { }))
-            {
-                Assert.True(target.SetValue("bar2"));
-            }
-            
-            Assert.Equal("bar2", data.Foo["foo"]);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public async Task Indexer_Only_Binding_Works()
-        {
-            var data = new[] { 1, 2, 3 };
-
-            var target = ExpressionObserver.Create(data, o => o[1]);
-
-            var value = await target.Take(1);
-
-            Assert.Equal(data[1], value);
-        }
-
-        private class NonIntegerIndexer : NotifyingBase
-        {
-            private readonly Dictionary<string, string> _storage = new Dictionary<string, string>();
-
-            public string this[string key]
-            {
-                get
-                {
-                    return _storage[key];
-                }
-                set
-                {
-                    _storage[key] = value;
-                    RaisePropertyChanged(CommonPropertyNames.IndexerName);
-                }
-            }
-        }
-    }
-}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Lifetime.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Lifetime.cs
deleted file mode 100644
index 612f3ff80..000000000
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Lifetime.cs
+++ /dev/null
@@ -1,112 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Reactive;
-using System.Reactive.Linq;
-using System.Reactive.Subjects;
-using Microsoft.Reactive.Testing;
-using Avalonia.Data.Core;
-using Xunit;
-using Avalonia.Markup.Parsers;
-
-namespace Avalonia.Base.UnitTests.Data.Core
-{
-    public class ExpressionObserverTests_Lifetime
-    {
-        [Fact]
-        public void Should_Complete_When_Source_Observable_Completes()
-        {
-            var source = new BehaviorSubject<object>(1);
-            var target = ExpressionObserver.Create<object, object>(source, o => o);
-            var completed = false;
-
-            target.Subscribe(_ => { }, () => completed = true);
-            source.OnCompleted();
-
-            Assert.True(completed);
-        }
-
-        [Fact]
-        public void Should_Complete_When_Source_Observable_Errors()
-        {
-            var source = new BehaviorSubject<object>(1);
-            var target = ExpressionObserver.Create<object, object>(source, o => o);
-            var completed = false;
-
-            target.Subscribe(_ => { }, () => completed = true);
-            source.OnError(new Exception());
-
-            Assert.True(completed);
-        }
-
-        [Fact]
-        public void Should_Complete_When_Update_Observable_Completes()
-        {
-            var update = new Subject<ValueTuple>();
-            var target = ExpressionObserver.Create(() => 1, o => o, update);
-            var completed = false;
-
-            target.Subscribe(_ => { }, () => completed = true);
-            update.OnCompleted();
-
-            Assert.True(completed);
-        }
-
-        [Fact]
-        public void Should_Complete_When_Update_Observable_Errors()
-        {
-            var update = new Subject<ValueTuple>();
-            var target = ExpressionObserver.Create(() => 1, o => o, update);
-            var completed = false;
-
-            target.Subscribe(_ => { }, () => completed = true);
-            update.OnError(new Exception());
-
-            Assert.True(completed);
-        }
-
-        [Fact]
-        public void Should_Unsubscribe_From_Source_Observable()
-        {
-            var scheduler = new TestScheduler();
-            var source = scheduler.CreateColdObservable(
-                OnNext(1, new { Foo = "foo" }));
-            var target = ExpressionObserver.Create(source, o => o.Foo);
-            var result = new List<object>();
-
-            using (target.Subscribe(x => result.Add(x)))
-            using (target.Subscribe(_ => { }))
-            {
-                scheduler.Start();
-            }
-
-            Assert.Equal(new[] { "foo" }, result);
-            Assert.All(source.Subscriptions, x => Assert.NotEqual(Subscription.Infinite, x.Unsubscribe));
-        }
-
-        [Fact]
-        public void Should_Unsubscribe_From_Update_Observable()
-        {
-            var scheduler = new TestScheduler();
-            var update = scheduler.CreateColdObservable<ValueTuple>();
-            var data = new { Foo = "foo" };
-            var target = ExpressionObserver.Create(() => data, o => o.Foo, update);
-            var result = new List<object>();
-
-            using (target.Subscribe(x => result.Add(x)))
-            using (target.Subscribe(_ => { }))
-            {
-                scheduler.Start();
-            }
-
-            Assert.Equal(new[] { "foo" }, result);
-            Assert.All(update.Subscriptions, x => Assert.NotEqual(Subscription.Infinite, x.Unsubscribe));
-
-            GC.KeepAlive(data);
-        }
-
-        private static Recorded<Notification<T>> OnNext<T>(long time, T value)
-        {
-            return new Recorded<Notification<T>>(time, Notification.CreateOnNext<T>(value));
-        }
-    }
-}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Negation.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Negation.cs
deleted file mode 100644
index 2f6707058..000000000
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Negation.cs
+++ /dev/null
@@ -1,42 +0,0 @@
-using System;
-using System.Reactive.Linq;
-using System.Threading.Tasks;
-using Avalonia.Data;
-using Avalonia.Data.Core;
-using Avalonia.Markup.Parsers;
-using Xunit;
-
-namespace Avalonia.Base.UnitTests.Data.Core
-{
-    public class ExpressionObserverTests_Negation
-    {
-        [Fact]
-        public async Task Should_Negate_Boolean_Value()
-        {
-            var data = new { Foo = true };
-            var target = ExpressionObserver.Create(data, o => !o.Foo);
-            var result = await target.Take(1);
-
-            Assert.False((bool)result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Can_SetValue_For_Valid_Value()
-        {
-            var data = new Test { Foo = true };
-            var target = ExpressionObserver.Create(data, o => !o.Foo);
-            target.Subscribe(_ => { });
-
-            Assert.True(target.SetValue(true));
-
-            Assert.False(data.Foo);
-        }
-
-        private class Test
-        {
-            public bool Foo { get; set; }
-        }
-    }
-}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Observable.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Observable.cs
deleted file mode 100644
index 4f88d2de7..000000000
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Observable.cs
+++ /dev/null
@@ -1,199 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Reactive.Linq;
-using System.Reactive.Subjects;
-using Avalonia.Data;
-using Avalonia.Data.Core;
-using Avalonia.Markup.Parsers;
-using Avalonia.Threading;
-using Avalonia.UnitTests;
-using Xunit;
-
-namespace Avalonia.Base.UnitTests.Data.Core
-{
-    public class ExpressionObserverTests_Observable
-    {
-        [Fact]
-        public void Should_Not_Get_Observable_Value_Without_Streaming()
-        {
-            using (var sync = UnitTestSynchronizationContext.Begin())
-            {
-                var source = new BehaviorSubject<string>("foo");
-                var data = new { Foo = source };
-                var target = ExpressionObserver.Create(data, o => o.Foo);
-                var result = new List<object>();
-
-                var sub = target.Subscribe(x => result.Add(x));
-                source.OnNext("bar");
-                sync.ExecutePostedCallbacks();
-
-                Assert.Equal(new[] { source }, result);
-
-                GC.KeepAlive(data);
-            }
-        }
-
-        [Fact]
-        public void Should_Get_Simple_Observable_Value()
-        {
-            using (var sync = UnitTestSynchronizationContext.Begin())
-            {
-                var source = new BehaviorSubject<string>("foo");
-                var data = new { Foo = source };
-                var target = ExpressionObserver.Create(data, o => o.Foo.StreamBinding());
-                var result = new List<object>();
-
-                var sub = target.Subscribe(x => result.Add(x));
-                source.OnNext("bar");
-                sync.ExecutePostedCallbacks();
-
-                Assert.Equal(new[] { "foo", "bar" }, result);
-
-                GC.KeepAlive(data);
-            }
-        }
-
-        [Fact]
-        public void Should_Get_Property_Value_From_Observable()
-        {
-            using (var sync = UnitTestSynchronizationContext.Begin())
-            {
-                var data = new Class1();
-                var target = ExpressionObserver.Create(data, o => o.Next.StreamBinding().Foo);
-                var result = new List<object>();
-
-                var sub = target.Subscribe(x => result.Add(x));
-                data.Next.OnNext(new Class2("foo"));
-                sync.ExecutePostedCallbacks();
-
-                Assert.Equal(new[] { "foo" }, result);
-
-                sub.Dispose();
-                // Forces WeakEvent compact
-                Dispatcher.UIThread.RunJobs();
-                Assert.Equal(0, data.PropertyChangedSubscriptionCount);
-
-                GC.KeepAlive(data);
-            }
-        }
-
-        [Fact]
-        public void Should_Get_Simple_Observable_Value_With_DataValidation_Enabled()
-        {
-            using (var sync = UnitTestSynchronizationContext.Begin())
-            {
-                var source = new BehaviorSubject<string>("foo");
-                var data = new { Foo = source };
-                var target = ExpressionObserver.Create(data, o => o.Foo.StreamBinding(), true);
-                var result = new List<object>();
-
-                var sub = target.Subscribe(x => result.Add(x));
-                source.OnNext("bar");
-                sync.ExecutePostedCallbacks();
-
-                // What does it mean to have data validation on an observable? Without a use-case
-                // it's hard to know what to do here so for the moment the value is returned.
-                Assert.Equal(new[] { "foo", "bar" }, result);
-
-                GC.KeepAlive(data);
-            }
-        }
-
-        [Fact]
-        public void Should_Get_Property_Value_From_Observable_With_DataValidation_Enabled()
-        {
-            using (var sync = UnitTestSynchronizationContext.Begin())
-            {
-                var data1 = new Class1();
-                var data2 = new Class2("foo");
-                var target = ExpressionObserver.Create(data1, o => o.Next.StreamBinding().Foo, true);
-                var result = new List<object>();
-
-                var sub = target.Subscribe(x => result.Add(x));
-                data1.Next.OnNext(data2);
-                sync.ExecutePostedCallbacks();
-                
-                // Forces WeakEvent compact
-                Dispatcher.UIThread.RunJobs();
-                Assert.Equal(new[] { new BindingNotification("foo") }, result);
-
-                sub.Dispose();
-                
-                // Forces WeakEvent compact
-                Dispatcher.UIThread.RunJobs();
-                
-                Assert.Equal(0, data1.PropertyChangedSubscriptionCount);
-
-                GC.KeepAlive(data1);
-                GC.KeepAlive(data2);
-            }
-        }
-
-        [Fact]
-        public void Should_Return_BindingNotification_If_Stream_Operator_Applied_To_Not_Supported_Type()
-        {
-            using (var sync = UnitTestSynchronizationContext.Begin())
-            {
-                var data = new NotStreamable();
-                var target = ExpressionObserver.Create(data, o => o.StreamBinding());
-                var result = new List<object>();
-
-                var sub = target.Subscribe(x => result.Add(x));
-                sync.ExecutePostedCallbacks();
-
-                Assert.Equal(
-                    new[]
-                    {
-                        new BindingNotification(
-                            new MarkupBindingChainException("Stream operator applied to unsupported type", "o => o.StreamBinding()", "^"),
-                            BindingErrorType.Error)
-                    },
-                    result);
-
-                sub.Dispose();
-
-                GC.KeepAlive(data);
-            }
-        }
-
-        [Fact]
-        public void Should_Work_With_Value_Type()
-        {
-            using (var sync = UnitTestSynchronizationContext.Begin())
-            {
-                var source = new BehaviorSubject<int>(1);
-                var data = new { Foo = source };
-                var target = ExpressionObserver.Create(data, o => o.Foo.StreamBinding());
-                var result = new List<int>();
-
-                var sub = target.Subscribe(x => result.Add((int)x));
-                source.OnNext(42);
-                sync.ExecutePostedCallbacks();
-
-                Assert.Equal(new[] { 1, 42 }, result);
-
-                GC.KeepAlive(data);
-            }
-        }
-
-        private class Class1 : NotifyingBase
-        {
-            public Subject<Class2> Next { get; } = new Subject<Class2>();
-        }
-
-        private class Class2 : NotifyingBase
-        {
-            public Class2(string foo)
-            {
-                Foo = foo;
-            }
-
-            public string Foo { get; }
-        }
-
-        private class NotStreamable
-        {
-            public object StreamBinding() { throw new InvalidOperationException(); }
-        }
-    }
-}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Property.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Property.cs
deleted file mode 100644
index 22d5645f7..000000000
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Property.cs
+++ /dev/null
@@ -1,738 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Reactive;
-using System.Reactive.Linq;
-using System.Reactive.Subjects;
-using System.Threading.Tasks;
-using Avalonia.Data;
-using Avalonia.Data.Core;
-using Avalonia.Threading;
-using Avalonia.UnitTests;
-using Microsoft.Reactive.Testing;
-using Xunit;
-
-namespace Avalonia.Base.UnitTests.Data.Core
-{
-    public class ExpressionObserverTests_Property
-    {
-        [Fact]
-        public async Task Should_Get_Simple_Property_Value()
-        {
-            var data = new { Foo = "foo" };
-            var target = ExpressionObserver.Create(data, o => o.Foo);
-            var result = await target.Take(1);
-
-            Assert.Equal("foo", result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Get_Simple_Property_Value_Type()
-        {
-            var data = new { Foo = "foo" };
-            var target = ExpressionObserver.Create(data, o => o.Foo);
-
-            target.Subscribe(_ => { });
-
-            Assert.Equal(typeof(string), target.ResultType);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public async Task Should_Get_Simple_Property_Value_Null()
-        {
-            var data = new { Foo = (string)null };
-            var target = ExpressionObserver.Create(data, o => o.Foo);
-            var result = await target.Take(1);
-
-            Assert.Null(result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public async Task Should_Get_Simple_Property_From_Base_Class()
-        {
-            var data = new Class3 { Foo = "foo" };
-            var target = ExpressionObserver.Create(data, o => o.Foo);
-            var result = await target.Take(1);
-
-            Assert.Equal("foo", result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public async Task Should_Return_BindingNotification_Error_For_Root_Null()
-        {
-            var target = ExpressionObserver.Create(default(Class3), o => o.Foo);
-            var result = await target.Take(1);
-
-            Assert.Equal(
-                new BindingNotification(
-                        new MarkupBindingChainException("Null value", "o => o.Foo", string.Empty),
-                        BindingErrorType.Error,
-                        AvaloniaProperty.UnsetValue),
-                result);
-        }
-
-        [Fact]
-        public async Task Should_Return_BindingNotification_Error_For_Root_UnsetValue()
-        {
-            var target = ExpressionObserver.Create(AvaloniaProperty.UnsetValue, o => (o as Class3).Foo);
-            var result = await target.Take(1);
-
-            Assert.Equal(
-                new BindingNotification(
-                        new MarkupBindingChainException("Null value", "o => (o As Class3).Foo", string.Empty),
-                        BindingErrorType.Error,
-                        AvaloniaProperty.UnsetValue),
-                result);
-        }
-
-        [Fact]
-        public async Task Should_Return_BindingNotification_Error_For_Observable_Root_Null()
-        {
-            var target = ExpressionObserver.Create(Observable.Return(default(Class3)), o => o.Foo);
-            var result = await target.Take(1);
-
-            Assert.Equal(
-                new BindingNotification(
-                        new MarkupBindingChainException("Null value", "o => o.Foo", string.Empty),
-                        BindingErrorType.Error,
-                        AvaloniaProperty.UnsetValue),
-                result);
-        }
-
-        [Fact]
-        public async void Should_Return_BindingNotification_Error_For_Observable_Root_UnsetValue()
-        {
-            var target = ExpressionObserver.Create<object, string>(Observable.Return(AvaloniaProperty.UnsetValue), o => (o as Class3).Foo);
-            var result = await target.Take(1);
-
-            Assert.Equal(
-                new BindingNotification(
-                        new MarkupBindingChainException("Null value", "o => (o As Class3).Foo", string.Empty),
-                        BindingErrorType.Error,
-                        AvaloniaProperty.UnsetValue),
-                result);
-            
-        }
-
-        [Fact]
-        public async Task Should_Get_Simple_Property_Chain()
-        {
-            var data = new { Foo = new { Bar = new { Baz = "baz" } } };
-            var target = ExpressionObserver.Create(data, o => o.Foo.Bar.Baz);
-            var result = await target.Take(1);
-
-            Assert.Equal("baz", result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Get_Simple_Property_Chain_Type()
-        {
-            var data = new { Foo = new { Bar = new { Baz = "baz" } } };
-            var target = ExpressionObserver.Create(data, o => o.Foo.Bar.Baz);
-
-            target.Subscribe(_ => { });
-
-            Assert.Equal(typeof(string), target.ResultType);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Return_BindingNotification_Error_For_Chain_With_Null_Value()
-        {
-            var data = new { Foo = default(Class1) };
-            var target = ExpressionObserver.Create(data, o => o.Foo.Foo.Length);
-            var result = new List<object>();
-
-            target.Subscribe(x => result.Add(x));
-
-            Assert.Equal(
-                new[]
-                {
-                    new BindingNotification(
-                        new MarkupBindingChainException("Null value", "o => o.Foo.Foo.Length", "Foo"),
-                        BindingErrorType.Error,
-                        AvaloniaProperty.UnsetValue),
-                },
-                result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Track_Simple_Property_Value()
-        {
-            var data = new Class1 { Foo = "foo" };
-            var target = ExpressionObserver.Create(data, o => o.Foo);
-            var result = new List<object>();
-
-            var sub = target.Subscribe(x => result.Add(x));
-            data.Foo = "bar";
-
-            Assert.Equal(new[] { "foo", "bar" }, result);
-
-            sub.Dispose();
-
-            // Forces WeakEvent compact
-            Dispatcher.UIThread.RunJobs();
-            
-            Assert.Equal(0, data.PropertyChangedSubscriptionCount);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Trigger_PropertyChanged_On_Null_Or_Empty_String()
-        {
-            var data = new Class1 { Bar = "foo" };
-            var target = ExpressionObserver.Create(data, o => o.Bar);
-            var result = new List<object>();
-
-            var sub = target.Subscribe(x => result.Add(x));
-
-            Assert.Equal(new[] { "foo" }, result);
-
-            data.Bar = "bar";
-
-            Assert.Equal(new[] { "foo" }, result);
-
-            data.RaisePropertyChanged(string.Empty);
-
-            Assert.Equal(new[] { "foo", "bar" }, result);
-
-            data.RaisePropertyChanged(null);
-
-            Assert.Equal(new[] { "foo", "bar", "bar" }, result);
-            
-            sub.Dispose();
-            
-            // Forces WeakEvent compact
-            Dispatcher.UIThread.RunJobs();
-
-            Assert.Equal(0, data.PropertyChangedSubscriptionCount);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Track_End_Of_Property_Chain_Changing()
-        {
-            var data = new Class1 { Next = new Class2 { Bar = "bar" } };
-            var target = ExpressionObserver.Create(data, o => (o.Next as Class2).Bar);
-            var result = new List<object>();
-
-            var sub = target.Subscribe(x => result.Add(x));
-            ((Class2)data.Next).Bar = "baz";
-            ((Class2)data.Next).Bar = null;
-
-            Assert.Equal(new[] { "bar", "baz", null }, result);
-
-            sub.Dispose();
-            // Forces WeakEvent compact
-            Dispatcher.UIThread.RunJobs();
-            
-            Assert.Equal(0, data.PropertyChangedSubscriptionCount);
-            Assert.Equal(0, data.Next.PropertyChangedSubscriptionCount);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Track_Property_Chain_Changing()
-        {
-            var data = new Class1 { Next = new Class2 { Bar = "bar" } };
-            var target = ExpressionObserver.Create(data, o => (o.Next as Class2).Bar);
-            var result = new List<object>();
-
-            var sub = target.Subscribe(x => result.Add(x));
-            var old = data.Next;
-            data.Next = new Class2 { Bar = "baz" };
-            data.Next = new Class2 { Bar = null };
-
-            Assert.Equal(new[] { "bar", "baz", null }, result);
-
-            sub.Dispose();
-            
-            // Forces WeakEvent compact
-            Dispatcher.UIThread.RunJobs();
-
-            Assert.Equal(0, data.PropertyChangedSubscriptionCount);
-            Assert.Equal(0, data.Next.PropertyChangedSubscriptionCount);
-            Assert.Equal(0, old.PropertyChangedSubscriptionCount);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Track_Property_Chain_Breaking_With_Null_Then_Mending()
-        {
-            var data = new Class1
-            {
-                Next = new Class2
-                {
-                    Next = new Class2
-                    {
-                        Bar = "bar"
-                    }
-                }
-            };
-
-            var target = ExpressionObserver.Create(data, o => ((o.Next as Class2).Next as Class2).Bar);
-            var result = new List<object>();
-
-            var sub = target.Subscribe(x => result.Add(x));
-            var old = data.Next;
-            data.Next = new Class2 { Bar = "baz" };
-            data.Next = old;
-
-            Assert.Equal(
-                new object[]
-                {
-                    "bar",
-                    new BindingNotification(
-                        new MarkupBindingChainException("Null value", "o => ((o.Next As Class2).Next As Class2).Bar", "Next.Next"),
-                        BindingErrorType.Error,
-                        AvaloniaProperty.UnsetValue),
-                    "bar"
-                },
-                result);
-
-            sub.Dispose();
-
-            // Forces WeakEvent compact
-            Dispatcher.UIThread.RunJobs();
-            
-            Assert.Equal(0, data.PropertyChangedSubscriptionCount);
-            Assert.Equal(0, data.Next.PropertyChangedSubscriptionCount);
-            Assert.Equal(0, old.PropertyChangedSubscriptionCount);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Track_Property_Chain_Breaking_With_Missing_Member_Then_Mending()
-        {
-            var data = new Class1 { Next = new Class2 { Bar = "bar" } };
-            var target = ExpressionObserver.Create(data, o => (o.Next as Class2).Bar);
-            var result = new List<object>();
-
-            var sub = target.Subscribe(x => result.Add(x));
-            var old = data.Next;
-            var breaking = new WithoutBar();
-            data.Next = breaking;
-            data.Next = new Class2 { Bar = "baz" };
-
-            Assert.Equal(
-                new object[]
-                {
-                    "bar",
-                    new BindingNotification(
-                        new MissingMemberException("Could not find a matching property accessor for 'Bar' on 'Avalonia.Base.UnitTests.Data.Core.ExpressionObserverTests_Property+WithoutBar'"),
-                        BindingErrorType.Error),
-                    "baz",
-                },
-                result);
-
-            sub.Dispose();
-            
-            // Forces WeakEvent compact
-            Dispatcher.UIThread.RunJobs();
-
-            Assert.Equal(0, data.PropertyChangedSubscriptionCount);
-            Assert.Equal(0, data.Next.PropertyChangedSubscriptionCount);
-            Assert.Equal(0, breaking.PropertyChangedSubscriptionCount);
-            Assert.Equal(0, old.PropertyChangedSubscriptionCount);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Empty_Expression_Should_Track_Root()
-        {
-            var data = new Class1 { Foo = "foo" };
-            var update = new Subject<ValueTuple>();
-            var target = ExpressionObserver.Create(() => data.Foo, o => o, update);
-            var result = new List<object>();
-
-            target.Subscribe(x => result.Add(x));
-
-            data.Foo = "bar";
-            update.OnNext(default);
-
-            Assert.Equal(new[] { "foo", "bar" }, result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Should_Track_Property_Value_From_Observable_Root()
-        {
-            var scheduler = new TestScheduler();
-            var source = scheduler.CreateColdObservable(
-                OnNext(1, new Class1 { Foo = "foo" }),
-                OnNext(2, new Class1 { Foo = "bar" }));
-            var target = ExpressionObserver.Create(source, o => o.Foo);
-            var result = new List<object>();
-
-            using (target.Subscribe(x => result.Add(x)))
-            {
-                scheduler.Start();
-            }
-
-            Assert.Equal(new[] { "foo", "bar" }, result);
-            Assert.All(source.Subscriptions, x => Assert.NotEqual(Subscription.Infinite, x.Unsubscribe));
-        }
-
-        [Fact]
-        public void Subscribing_Multiple_Times_Should_Return_Values_To_All()
-        {
-            var data = new Class1 { Foo = "foo" };
-            var target = ExpressionObserver.Create(data, o => o.Foo);
-            var result1 = new List<object>();
-            var result2 = new List<object>();
-            var result3 = new List<object>();
-
-            target.Subscribe(x => result1.Add(x));
-            target.Subscribe(x => result2.Add(x));
-
-            data.Foo = "bar";
-
-            target.Subscribe(x => result3.Add(x));
-
-            Assert.Equal(new[] { "foo", "bar" }, result1);
-            Assert.Equal(new[] { "foo", "bar" }, result2);
-            Assert.Equal(new[] { "bar" }, result3);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Subscribing_Multiple_Times_Should_Only_Add_PropertyChanged_Handlers_Once()
-        {
-            var data = new Class1 { Foo = "foo" };
-            var target = ExpressionObserver.Create(data, o => o.Foo);
-
-            var sub1 = target.Subscribe(x => { });
-            var sub2 = target.Subscribe(x => { });
-
-            Assert.Equal(1, data.PropertyChangedSubscriptionCount);
-
-            sub1.Dispose();
-            sub2.Dispose();
-
-            // Forces WeakEvent compact
-            Dispatcher.UIThread.RunJobs();
-            
-            Assert.Equal(0, data.PropertyChangedSubscriptionCount);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void SetValue_Should_Set_Simple_Property_Value()
-        {
-            var data = new Class1 { Foo = "foo" };
-            var target = ExpressionObserver.Create(data, o => o.Foo);
-
-            using (target.Subscribe(_ => { }))
-            {
-                Assert.True(target.SetValue("bar"));
-            }
-
-            Assert.Equal("bar", data.Foo);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void SetValue_Should_Set_Property_At_The_End_Of_Chain()
-        {
-            var data = new Class1 { Next = new Class2 { Bar = "bar" } };
-            var target = ExpressionObserver.Create(data, o => (o.Next as Class2).Bar);
-
-            using (target.Subscribe(_ => { }))
-            {
-                Assert.True(target.SetValue("baz"));
-            }
-
-            Assert.Equal("baz", ((Class2)data.Next).Bar);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void SetValue_Should_Return_False_For_Missing_Property()
-        {
-            var data = new Class1 { Next = new WithoutBar() };
-            var target = ExpressionObserver.Create(data, o => (o.Next as Class2).Bar);
-
-            using (target.Subscribe(_ => { }))
-            {
-                Assert.False(target.SetValue("baz"));
-            }
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void SetValue_Should_Notify_New_Value_With_Inpc()
-        {
-            var data = new Class1();
-            var target = ExpressionObserver.Create(data, o => o.Foo);
-            var result = new List<object>();
-
-            target.Subscribe(x => result.Add(x));
-            target.SetValue("bar");
-
-            Assert.Equal(new[] { null, "bar" }, result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void SetValue_Should_Notify_New_Value_Without_Inpc()
-        {
-            var data = new Class1();
-            var target = ExpressionObserver.Create(data, o => o.Bar);
-            var result = new List<object>();
-
-            target.Subscribe(x => result.Add(x));
-            target.SetValue("bar");
-
-            Assert.Equal(new[] { null, "bar" }, result);
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void SetValue_Should_Return_False_For_Missing_Object()
-        {
-            var data = new Class1();
-            var target = ExpressionObserver.Create(data, o => (o.Next as Class2).Bar);
-
-            using (target.Subscribe(_ => { }))
-            {
-                Assert.False(target.SetValue("baz"));
-            }
-
-            GC.KeepAlive(data);
-        }
-
-        [Fact]
-        public void Can_Replace_Root()
-        {
-            var first = new Class1 { Foo = "foo" };
-            var second = new Class1 { Foo = "bar" };
-            var root = first;
-            var update = new Subject<ValueTuple>();
-            var target = ExpressionObserver.Create(() => root, o => o.Foo, update);
-            var result = new List<object>();
-            var sub = target.Subscribe(x => result.Add(x));
-
-            root = second;
-            update.OnNext(default);
-            root = null;
-            update.OnNext(default);
-
-            Assert.Equal(
-                new object[]
-                {
-                    "foo",
-                    "bar",
-                    new BindingNotification(
-                        new MarkupBindingChainException("Null value", "o => o.Foo", string.Empty),
-                        BindingErrorType.Error,
-                        AvaloniaProperty.UnsetValue)
-                },
-                result);
-
-            // Forces WeakEvent compact
-            Dispatcher.UIThread.RunJobs();
-            Assert.Equal(0, first.PropertyChangedSubscriptionCount);
-            Assert.Equal(0, second.PropertyChangedSubscriptionCount);
-
-            GC.KeepAlive(first);
-            GC.KeepAlive(second);
-        }
-
-        [Fact]
-        public void Should_Not_Keep_Source_Alive()
-        {
-            Func<Tuple<ExpressionObserver, WeakReference>> run = () =>
-            {
-                var source = new Class1 { Foo = "foo" };
-                var target = ExpressionObserver.Create(source, o => o.Foo);
-                return Tuple.Create(target, new WeakReference(source));
-            };
-
-            var result = run();
-            result.Item1.Subscribe(x => { });
-
-            // Mono trickery
-            GC.Collect(2);
-            GC.WaitForPendingFinalizers();
-            GC.WaitForPendingFinalizers();
-            GC.Collect(2);
-            
-
-            Assert.Null(result.Item2.Target);
-        }
-
-        [Fact]
-        public void Should_Not_Throw_Exception_On_Unsubscribe_When_Already_Unsubscribed()
-        {
-            var source = new Class1 { Foo = "foo" };
-            var target = new PropertyAccessorNode("Foo", false);
-            Assert.NotNull(target);
-            target.Target = new WeakReference<object>(source);
-            target.Subscribe(_ => { });
-            target.Unsubscribe();
-            target.Unsubscribe();
-            Assert.True(true);
-        }
-
-        [Fact]
-        public void Should_Not_Throw_Exception_When_Enabling_Data_Validation_On_Missing_Member()
-        {
-            var source = new Class1();
-            var target = new PropertyAccessorNode("NotFound", true);
-
-            target.Target = new WeakReference<object>(source);
-
-            var result = new List<object>();
-
-            target.Subscribe(x => result.Add(x));
-
-            Assert.Equal(
-                new object[]
-                {
-                    new BindingNotification(
-                        new MissingMemberException("Could not find a matching property accessor for 'NotFound' on 'Avalonia.Base.UnitTests.Data.Core.ExpressionObserverTests_Property+Class1'"),
-                        BindingErrorType.Error),
-                },
-                result);
-        }
-
-        [Fact]
-        public void Should_Not_Throw_Exception_On_Duplicate_Properties()
-        {
-            // Repro of https://github.com/AvaloniaUI/Avalonia/issues/4733.
-            var source = new MyViewModel();
-            var target = new PropertyAccessorNode("Name", false);
-            
-            target.Target = new WeakReference<object>(source);
-            
-            var result = new List<object>();
-            
-            target.Subscribe(x => result.Add(x));
-        }
-
-        [Fact]
-        public void RootGetter_Is_Reevaluated_On_Subscribe()
-        {
-            var data = "foo";
-            var target = new ExpressionObserver(() => data, new EmptyExpressionNode(), new Subject<ValueTuple>(), null);
-            var result = new List<object>();
-            var sub = target.Subscribe(x => result.Add(x));
-
-            Assert.Equal(new object[] { "foo" }, result);
-
-            sub.Dispose();
-            data = "bar";
-
-            target.Subscribe(x => result.Add(x));
-
-            Assert.Equal(new object[] { "foo", "bar" }, result);
-        }
-
-        public class MyViewModelBase { public object Name => "Name"; }
-        
-        public class MyViewModel : MyViewModelBase { public new string Name => "NewName"; }
-
-        private interface INext
-        {
-            int PropertyChangedSubscriptionCount { get; }
-        }
-
-        private class Class1 : NotifyingBase
-        {
-            private string _foo;
-            private INext _next;
-
-            public string Foo
-            {
-                get { return _foo; }
-                set
-                {
-                    _foo = value;
-                    RaisePropertyChanged(nameof(Foo));
-                }
-            }
-
-            private string _bar;
-            public string Bar
-            {
-                get { return _bar; }
-                set { _bar = value; }
-            }
-
-            public INext Next
-            {
-                get { return _next; }
-                set
-                {
-                    _next = value;
-                    RaisePropertyChanged(nameof(Next));
-                }
-            }
-        }
-
-        private class Class2 : NotifyingBase, INext
-        {
-            private string _bar;
-            private INext _next;
-
-            public string Bar
-            {
-                get { return _bar; }
-                set
-                {
-                    _bar = value;
-                    RaisePropertyChanged(nameof(Bar));
-                }
-            }
-
-            public INext Next
-            {
-                get { return _next; }
-                set
-                {
-                    _next = value;
-                    RaisePropertyChanged(nameof(Next));
-                }
-            }
-        }
-
-        private class Class3 : Class1
-        {
-        }
-
-        private class WithoutBar : NotifyingBase, INext
-        {
-        }
-
-        private static Recorded<Notification<T>> OnNext<T>(long time, T value)
-        {
-            return new Recorded<Notification<T>>(time, Notification.CreateOnNext<T>(value));
-        }
-    }
-}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_SetValue.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_SetValue.cs
deleted file mode 100644
index b1cc42488..000000000
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_SetValue.cs
+++ /dev/null
@@ -1,111 +0,0 @@
-using System;
-using System.Reactive.Linq;
-using System.Reactive.Subjects;
-using Avalonia.Data.Core;
-using Avalonia.Markup.Parsers;
-using Avalonia.UnitTests;
-using Xunit;
-
-namespace Avalonia.Base.UnitTests.Data.Core
-{
-    public class ExpressionObserverTests_SetValue
-    {
-        [Fact]
-        public void Should_Set_Simple_Property_Value()
-        {
-            var data = new { Foo = "foo" };
-            var target = ExpressionObserver.Create(data, o => o.Foo);
-
-            using (target.Subscribe(_ => { }))
-            {
-                target.SetValue("bar");
-            }
-
-            Assert.Equal("foo", data.Foo);
-        }
-
-        [Fact]
-        public void Should_Set_Value_On_Simple_Property_Chain()
-        {
-            var data = new Class1 { Foo = new Class2 { Bar = "bar" } };
-            var target = ExpressionObserver.Create(data, o => o.Foo.Bar);
-
-
-            using (target.Subscribe(_ => { }))
-            {
-                target.SetValue("foo");
-            }
-
-            Assert.Equal("foo", data.Foo.Bar);
-        }
-
-        [Fact]
-        public void Should_Not_Try_To_Set_Value_On_Broken_Chain()
-        {
-            var data = new Class1 { Foo = new Class2 { Bar = "bar" } };
-            var target = ExpressionObserver.Create(data, o => o.Foo.Bar);
-
-            // Ensure the ExpressionObserver's subscriptions are kept active.
-            using (target.OfType<string>().Subscribe(x => { }))
-            {
-                data.Foo = null;
-                Assert.False(target.SetValue("foo"));
-            }
-
-        }
-
-        /// <summary>
-        /// Test for #831 - Bound properties are incorrectly updated when changing tab items.
-        /// </summary>
-        /// <remarks>
-        /// There was a bug whereby pushing a null as the ExpressionObserver root didn't update
-        /// the leaf node, cauing a subsequent SetValue to update an object that should have become
-        /// unbound.
-        /// </remarks>
-        [Fact]
-        public void Pushing_Null_To_RootObservable_Updates_Leaf_Node()
-        {
-            var data = new Class1 { Foo = new Class2 { Bar = "bar" } };
-            var rootObservable = new BehaviorSubject<Class1>(data);
-            var target = ExpressionObserver.Create(rootObservable, o => o.Foo.Bar);
-
-            using (target.Subscribe(_ => { }))
-            {
-                rootObservable.OnNext(null);
-                target.SetValue("baz");
-                Assert.Equal("bar", data.Foo.Bar);
-            }
-
-        }
-
-        private class Class1 : NotifyingBase
-        {
-            private Class2 _foo;
-
-            public Class2 Foo
-            {
-                get { return _foo; }
-                set
-                {
-                    _foo = value;
-                    RaisePropertyChanged(nameof(Foo));
-                }
-            }
-        }
-
-        private class Class2 : NotifyingBase
-        {
-            private string _bar;
-
-            public string Bar
-            {
-                get { return _bar; }
-                set
-                {
-                    _bar = value;
-                    RaisePropertyChanged(nameof(Bar));
-                }
-            }
-        }
-    }
-}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Task.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Task.cs
deleted file mode 100644
index cf70a617b..000000000
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Task.cs
+++ /dev/null
@@ -1,173 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Reactive.Linq;
-using System.Threading.Tasks;
-using Avalonia.Data;
-using Avalonia.Data.Core;
-using Avalonia.Markup.Parsers;
-using Avalonia.UnitTests;
-using Xunit;
-
-namespace Avalonia.Base.UnitTests.Data.Core
-{
-    public class ExpressionObserverTests_Task
-    {
-        [Fact]
-        public void Should_Not_Get_Task_Result_Without_StreamBinding()
-        {
-            using (var sync = UnitTestSynchronizationContext.Begin())
-            {
-                var tcs = new TaskCompletionSource<string>();
-                var data = new { Foo = tcs.Task };
-                var target = ExpressionObserver.Create(data, o => o.Foo);
-                var result = new List<object>();
-
-                var sub = target.Subscribe(x => result.Add(x));
-                tcs.SetResult("foo");
-                sync.ExecutePostedCallbacks();
-
-                Assert.Single(result);
-                Assert.IsType<Task<string>>(result[0]);
-
-                GC.KeepAlive(data);
-            }
-        }
-
-        [Fact]
-        public void Should_Get_Completed_Task_Value()
-        {
-            using (var sync = UnitTestSynchronizationContext.Begin())
-            {
-                var data = new { Foo = Task.FromResult("foo") };
-                var target = ExpressionObserver.Create(data, o => o.Foo.StreamBinding());
-                var result = new List<object>();
-
-                var sub = target.Subscribe(x => result.Add(x));
-
-                Assert.Equal(new[] { "foo" }, result);
-
-                GC.KeepAlive(data);
-            }
-        }
-
-        [Fact]
-        public void Should_Get_Property_Value_From_Task()
-        {
-            using (var sync = UnitTestSynchronizationContext.Begin())
-            {
-                var tcs = new TaskCompletionSource<Class2>();
-                var data = new Class1(tcs.Task);
-                var target = ExpressionObserver.Create(data, o => o.Next.StreamBinding().Foo);
-                var result = new List<object>();
-
-                var sub = target.Subscribe(x => result.Add(x));
-                tcs.SetResult(new Class2("foo"));
-                sync.ExecutePostedCallbacks();
-
-                Assert.Equal(new[] { "foo" }, result);
-
-                GC.KeepAlive(data);
-            }
-        }
-
-        [Fact]
-        public void Should_Return_BindingNotification_Error_On_Task_Exception()
-        {
-            using (var sync = UnitTestSynchronizationContext.Begin())
-            {
-                var tcs = new TaskCompletionSource<string>();
-                var data = new { Foo = tcs.Task };
-                var target = ExpressionObserver.Create(data, o => o.Foo.StreamBinding());
-                var result = new List<object>();
-
-                var sub = target.Subscribe(x => result.Add(x));
-                tcs.SetException(new NotSupportedException());
-                sync.ExecutePostedCallbacks();
-
-                Assert.Equal(
-                    new[] 
-                    {
-                        new BindingNotification(
-                            new AggregateException(new NotSupportedException()),
-                            BindingErrorType.Error)
-                    }, 
-                    result);
-
-                GC.KeepAlive(data);
-            }
-        }
-
-        [Fact]
-        public void Should_Return_BindingNotification_Error_For_Faulted_Task()
-        {
-            using (var sync = UnitTestSynchronizationContext.Begin())
-            {
-                var data = new { Foo = TaskFromException(new NotSupportedException()) };
-                var target = ExpressionObserver.Create(data, o => o.Foo.StreamBinding());
-                var result = new List<object>();
-
-                var sub = target.Subscribe(x => result.Add(x));
-
-                Assert.Equal(
-                    new[]
-                    {
-                        new BindingNotification(
-                            new AggregateException(new NotSupportedException()),
-                            BindingErrorType.Error)
-                    },
-                    result);
-
-                GC.KeepAlive(data);
-            }
-        }
-
-        [Fact]
-        public void Should_Get_Simple_Task_Value_With_Data_DataValidation_Enabled()
-        {
-            using (var sync = UnitTestSynchronizationContext.Begin())
-            {
-                var tcs = new TaskCompletionSource<string>();
-                var data = new { Foo = tcs.Task };
-                var target = ExpressionObserver.Create(data, o => o.Foo.StreamBinding(), true);
-                var result = new List<object>();
-
-                var sub = target.Subscribe(x => result.Add(x));
-                tcs.SetResult("foo");
-                sync.ExecutePostedCallbacks();
-
-                // What does it mean to have data validation on a Task? Without a use-case it's
-                // hard to know what to do here so for the moment the value is returned.
-                Assert.Equal(new [] { "foo" }, result);
-
-                GC.KeepAlive(data);
-            }
-        }
-
-        private static Task TaskFromException(Exception e)
-        {
-            var tcs = new TaskCompletionSource<object>();
-            tcs.SetException(e);
-            return tcs.Task;
-        }
-
-        private class Class1 : NotifyingBase
-        {
-            public Class1(Task<Class2> next)
-            {
-                Next = next;
-            }
-
-            public Task<Class2> Next { get; }
-        }
-
-        private class Class2 : NotifyingBase
-        {
-            public Class2(string foo)
-            {
-                Foo = foo;
-            }
-
-            public string Foo { get; }
-        }
-    }
-}
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/Plugins/ExceptionValidationPluginTests.cs b/tests/Avalonia.Base.UnitTests/Data/Core/Plugins/ExceptionValidationPluginTests.cs
index 5e7de08fc..73bb9ba2f 100644
--- a/tests/Avalonia.Base.UnitTests/Data/Core/Plugins/ExceptionValidationPluginTests.cs
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/Plugins/ExceptionValidationPluginTests.cs
@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Linq;
 using Avalonia.Data;
 using Avalonia.Data.Core.Plugins;
 using Avalonia.UnitTests;
diff --git a/tests/Avalonia.Base.UnitTests/PropertyStore/ValueStoreTests_Frames.cs b/tests/Avalonia.Base.UnitTests/PropertyStore/ValueStoreTests_Frames.cs
index 3a307447a..8b5430247 100644
--- a/tests/Avalonia.Base.UnitTests/PropertyStore/ValueStoreTests_Frames.cs
+++ b/tests/Avalonia.Base.UnitTests/PropertyStore/ValueStoreTests_Frames.cs
@@ -99,7 +99,23 @@ namespace Avalonia.Base.UnitTests.PropertyStore
         }
 
         [Fact]
-        public void Completing_Binding_Removes_ImmediateValueFrame()
+        public void Disposing_Binding_Removes_ImmediateValueFrame()
+        {
+            var target = new Class1();
+            var source = new Binding { Priority = BindingPriority.Style };
+            var expression = target.Bind(Class1.FooProperty, source);
+
+            var valueStore = target.GetValueStore();
+            Assert.Equal(1, valueStore.Frames.Count);
+            Assert.IsType<ImmediateValueFrame>(valueStore.Frames[0]);
+
+            expression.Dispose();
+
+            Assert.Equal(0, valueStore.Frames.Count);
+        }
+
+        [Fact]
+        public void Completing_Observable_Removes_ImmediateValueFrame()
         {
             var target = new Class1();
             var source = new BehaviorSubject<BindingValue<string>>("foo");
diff --git a/tests/Avalonia.Base.UnitTests/Styling/SetterTests.cs b/tests/Avalonia.Base.UnitTests/Styling/SetterTests.cs
index f064841c8..0551fa5bc 100644
--- a/tests/Avalonia.Base.UnitTests/Styling/SetterTests.cs
+++ b/tests/Avalonia.Base.UnitTests/Styling/SetterTests.cs
@@ -6,7 +6,6 @@ using Avalonia.Controls.Templates;
 using Avalonia.Data;
 using Avalonia.Data.Converters;
 using Avalonia.Media;
-using Avalonia.PropertyStore;
 using Avalonia.Styling;
 using Avalonia.UnitTests;
 using Moq;
@@ -31,9 +30,7 @@ namespace Avalonia.Base.UnitTests.Styling
         {
             var control = new TextBlock();
             var subject = new BehaviorSubject<object>("foo");
-            var descriptor = InstancedBinding.OneWay(subject);
-            var binding = Mock.Of<IBinding>(x => x.Initiate(control, TextBlock.TagProperty, null, false) == descriptor);
-            var style = Mock.Of<IStyle>();
+            var binding = subject.ToBinding();
             var setter = new Setter(TextBlock.TagProperty, binding);
 
             Apply(setter, control);
@@ -46,9 +43,7 @@ namespace Avalonia.Base.UnitTests.Styling
         {
             var control = new TextBlock();
             var subject = new BehaviorSubject<object>(AvaloniaProperty.UnsetValue);
-            var descriptor = InstancedBinding.OneWay(subject);
-            var binding = Mock.Of<IBinding>(x => x.Initiate(control, TextBlock.TagProperty, null, false) == descriptor);
-            var style = Mock.Of<IStyle>();
+            var binding = subject.ToBinding();
             var setter = new Setter(TextBlock.TagProperty, binding);
 
             Apply(setter, control);
diff --git a/tests/Avalonia.Base.UnitTests/Styling/StyleTests.cs b/tests/Avalonia.Base.UnitTests/Styling/StyleTests.cs
index b44078cae..2ed9ab4e4 100644
--- a/tests/Avalonia.Base.UnitTests/Styling/StyleTests.cs
+++ b/tests/Avalonia.Base.UnitTests/Styling/StyleTests.cs
@@ -54,6 +54,29 @@ namespace Avalonia.Base.UnitTests.Styling
             Assert.Equal("foodefault", target.Foo);
         }
 
+        [Fact]
+        public void Style_With_Class_Selector_Should_Update_And_Restore_Value_With_TemplateBinding()
+        {
+            Style style = new Style(x => x.OfType<Class1>().Class("foo"))
+            {
+                Setters =
+                {
+                    new Setter(Class1.FooProperty, "Foo"),
+                },
+            };
+
+            var templatedParent = new Class1 { Foo = "unset-foo" };
+            var target = new Class1 { TemplatedParent = templatedParent };
+            target.Bind(Class1.FooProperty, new TemplateBinding(Class1.FooProperty), BindingPriority.Template);
+
+            StyleHelpers.TryAttach(style, target);
+            Assert.Equal("unset-foo", target.Foo);
+            target.Classes.Add("foo");
+            Assert.Equal("Foo", target.Foo);
+            target.Classes.Remove("foo");
+            Assert.Equal("unset-foo", target.Foo);
+        }
+
         [Fact]
         public void Style_With_No_Selector_Should_Apply_To_Containing_Control()
         {
diff --git a/tests/Avalonia.Base.UnitTests/VisualTests.cs b/tests/Avalonia.Base.UnitTests/VisualTests.cs
index be0ea41a7..aaf6b9992 100644
--- a/tests/Avalonia.Base.UnitTests/VisualTests.cs
+++ b/tests/Avalonia.Base.UnitTests/VisualTests.cs
@@ -254,55 +254,6 @@ namespace Avalonia.Base.UnitTests
             Assert.Null(tr);
         }
 
-        [Fact]
-        public void Should_Not_Log_Binding_Error_When_Not_Attached_To_Logical_Tree()
-        {
-            var target = new Decorator { DataContext = "foo" };
-            var called = false;
-
-            LogCallback checkLogMessage = (level, area, src, mt, pv) =>
-            {
-                if (level >= Avalonia.Logging.LogEventLevel.Warning)
-                {
-                    called = true;
-                }
-            };
-
-            using (TestLogSink.Start(checkLogMessage))
-            {
-                target.Bind(Decorator.TagProperty, new Binding("Foo"));
-            }
-
-            Assert.False(called);
-        }
-
-        [Fact]
-        public void Should_Log_Binding_Error_When_Attached_To_Logical_Tree()
-        {
-            var target = new Decorator();
-            var root = new TestRoot { Child = target, DataContext = "foo" };
-            var called = 0;
-
-            LogCallback checkLogMessage = (level, area, src, mt, pv) =>
-            {
-                if (level >= Avalonia.Logging.LogEventLevel.Warning)
-                {
-                    Assert.Equal("Error in binding to {Target}.{Property}: {Message}", mt);
-                    Assert.Same(target, pv[0]);
-                    Assert.Equal(Decorator.TagProperty, pv[1]);
-                    Assert.Equal("Could not find a matching property accessor for 'Foo' on 'foo'", pv[2]);
-                    ++called;
-                }
-            };
-
-            using (TestLogSink.Start(checkLogMessage))
-            {
-                target.Bind(Decorator.TagProperty, new Binding("Foo"));
-            }
-
-            Assert.Equal(1, called);
-        }
-
         [Fact]
         public void Changing_ZIndex_Should_InvalidateVisual()
         {
diff --git a/tests/Avalonia.Benchmarks/Data/Binding_Setup.cs b/tests/Avalonia.Benchmarks/Data/Binding_Setup.cs
new file mode 100644
index 000000000..84f5bec10
--- /dev/null
+++ b/tests/Avalonia.Benchmarks/Data/Binding_Setup.cs
@@ -0,0 +1,58 @@
+using Avalonia.Controls;
+using Avalonia.Data;
+using BenchmarkDotNet.Attributes;
+
+namespace Avalonia.Benchmarks.Data;
+
+[MemoryDiagnoser]
+public class Binding_Setup
+{
+    private TestData _data = new();
+    private TestControl _target = new();
+
+    public Binding_Setup()
+    {
+        _target.DataContext = _data;
+    }
+
+    [Benchmark]
+    public void Setup_DataContext_Property_Binding_OneWay()
+    {
+        var target = _target;
+        var binding = new Binding(nameof(_data.IntValue));
+
+        for (var i = 0; i < 100; ++i)
+        {
+            using var d = target.Bind(TestControl.IntValueProperty, binding);
+        }
+    }
+
+    [Benchmark]
+    public void Setup_DataContext_Property_Binding_TwoWay()
+    {
+        var target = _target;
+        var binding = new Binding(nameof(_data.IntValue), mode: BindingMode.TwoWay);
+
+        for (var i = 0; i < 100; ++i)
+        {
+            using var d = target.Bind(TestControl.IntValueProperty, binding);
+        }
+    }
+
+    private class TestControl : Control
+    {
+        public static readonly StyledProperty<int> IntValueProperty =
+            AvaloniaProperty.Register<TestControl, int>(nameof(IntValue));
+
+        public int IntValue
+        {
+            get => GetValue(IntValueProperty);
+            set => SetValue(IntValueProperty, value);
+        }
+    }
+
+    private class TestData
+    {
+        public int IntValue { get; set; }
+    }
+}
diff --git a/tests/Avalonia.Benchmarks/Data/Binding_Values.cs b/tests/Avalonia.Benchmarks/Data/Binding_Values.cs
new file mode 100644
index 000000000..7cf30eee4
--- /dev/null
+++ b/tests/Avalonia.Benchmarks/Data/Binding_Values.cs
@@ -0,0 +1,65 @@
+using Avalonia.Controls;
+using Avalonia.Data;
+using BenchmarkDotNet.Attributes;
+
+namespace Avalonia.Benchmarks.Data;
+
+[MemoryDiagnoser]
+public class Binding_Values
+{
+    private TestData _data = new();
+    private TestControl _target = new();
+
+    public Binding_Values()
+    {
+        _target.DataContext = _data;
+    }
+
+    [Benchmark]
+    public void Produce_DataContext_Property_Binding_Value_OneWay()
+    {
+        _data.IntValue = -1;
+
+        var target = _target;
+        var binding = new Binding(nameof(_data.IntValue));
+        using var d = target.Bind(TestControl.IntValueProperty, binding);
+
+        for (var i = 0; i < 100; ++i)
+        {
+            _data.IntValue = i;
+        }
+    }
+
+    [Benchmark]
+    public void Produce_DataContext_Property_Binding_Value_TwoWay()
+    {
+        _data.IntValue = -1;
+
+        var target = _target;
+        var binding = new Binding(nameof(_data.IntValue), mode: BindingMode.TwoWay);
+        using var d = target.Bind(TestControl.IntValueProperty, binding);
+
+        for (var i = 0; i < 100; ++i)
+        {
+            _data.IntValue = i * 2;
+            target.IntValue = (i * 2) + 1;
+        }
+    }
+
+    private class TestControl : Control
+    {
+        public static readonly StyledProperty<int> IntValueProperty =
+            AvaloniaProperty.Register<TestControl, int>(nameof(IntValue));
+
+        public int IntValue
+        {
+            get => GetValue(IntValueProperty);
+            set => SetValue(IntValueProperty, value);
+        }
+    }
+
+    private class TestData
+    {
+        public int IntValue { get; set; }
+    }
+}
diff --git a/tests/Avalonia.Benchmarks/Data/BindingsBenchmark.cs b/tests/Avalonia.Benchmarks/Data/BindingsBenchmark.cs
deleted file mode 100644
index a320f0706..000000000
--- a/tests/Avalonia.Benchmarks/Data/BindingsBenchmark.cs
+++ /dev/null
@@ -1,59 +0,0 @@
-using Avalonia.Data;
-using BenchmarkDotNet.Attributes;
-
-namespace Avalonia.Benchmarks.Data
-{
-    [MemoryDiagnoser, InProcess]
-    public class BindingsBenchmark
-    {
-        [Benchmark]
-        public void TwoWayBinding_Via_Binding()
-        {
-            var instance = new TestClass();
-
-            var binding = new Binding(nameof(TestClass.BoundValue), BindingMode.TwoWay)
-            {
-                Source = instance
-            };
-
-            instance.Bind(TestClass.IntValueProperty, binding);
-        }
-
-        [Benchmark]
-        public void UpdateTwoWayBinding_Via_Binding()
-        {
-            var instance = new TestClass();
-
-            var binding = new Binding(nameof(TestClass.BoundValue), BindingMode.TwoWay)
-            {
-                Source = instance
-            };
-
-            instance.Bind(TestClass.IntValueProperty, binding);
-            for (int i = 0; i < 60; i++)
-            {
-                instance.IntValue = i;
-            }
-        }
-        private class TestClass : AvaloniaObject
-        {
-            public static readonly StyledProperty<int> IntValueProperty =
-                AvaloniaProperty.Register<TestClass, int>(nameof(IntValue));
-
-            public static readonly StyledProperty<int> BoundValueProperty =
-                AvaloniaProperty.Register<TestClass, int>(nameof(BoundValue));
-
-            public int IntValue
-            {
-                get => GetValue(IntValueProperty);
-                set => SetValue(IntValueProperty, value);
-            }
-
-            public int BoundValue
-            {
-                get => GetValue(BoundValueProperty);
-                set => SetValue(BoundValueProperty, value);
-            }
-        }
-    }
-}
diff --git a/tests/Avalonia.Benchmarks/Data/PropertyAccessorBenchmarks.cs b/tests/Avalonia.Benchmarks/Data/PropertyAccessorBenchmarks.cs
index 6c5e0d3b5..87b8dd652 100644
--- a/tests/Avalonia.Benchmarks/Data/PropertyAccessorBenchmarks.cs
+++ b/tests/Avalonia.Benchmarks/Data/PropertyAccessorBenchmarks.cs
@@ -8,7 +8,7 @@ namespace Avalonia.Benchmarks.Data
     public class PropertyAccessorBenchmarks
     {
         private readonly InpcPropertyAccessorPlugin _inpcPlugin = new InpcPropertyAccessorPlugin();
-        private readonly MethodAccessorPlugin _methodPlugin = new MethodAccessorPlugin();
+        private readonly ReflectionMethodAccessorPlugin _methodPlugin = new ReflectionMethodAccessorPlugin();
         private readonly AccessorTestObject _targetStrongRef = new AccessorTestObject();
         private readonly WeakReference<object> _targetWeakRef;
 
diff --git a/tests/Avalonia.Benchmarks/Data/PropertyAccessorPluginBenchmarks.cs b/tests/Avalonia.Benchmarks/Data/PropertyAccessorPluginBenchmarks.cs
index 75e3269e3..6a6792d5b 100644
--- a/tests/Avalonia.Benchmarks/Data/PropertyAccessorPluginBenchmarks.cs
+++ b/tests/Avalonia.Benchmarks/Data/PropertyAccessorPluginBenchmarks.cs
@@ -17,7 +17,7 @@ namespace Avalonia.Benchmarks.Data
             _oldPlugins = new List<IPropertyAccessorPlugin>
             {
                 new AvaloniaPropertyAccessorPlugin(),
-                new MethodAccessorPlugin(),
+                new ReflectionMethodAccessorPlugin(),
                 new InpcPropertyAccessorPlugin()
             };
 
@@ -25,7 +25,7 @@ namespace Avalonia.Benchmarks.Data
             {
                 new AvaloniaPropertyAccessorPlugin(),
                 new InpcPropertyAccessorPlugin(),
-                new MethodAccessorPlugin()
+                new ReflectionMethodAccessorPlugin()
             };
         }
 
diff --git a/tests/Avalonia.Benchmarks/Data/TemplateBinding_Setup.cs b/tests/Avalonia.Benchmarks/Data/TemplateBinding_Setup.cs
new file mode 100644
index 000000000..eee61fbb5
--- /dev/null
+++ b/tests/Avalonia.Benchmarks/Data/TemplateBinding_Setup.cs
@@ -0,0 +1,46 @@
+using Avalonia.Controls;
+using Avalonia.Data;
+using BenchmarkDotNet.Attributes;
+
+namespace Avalonia.Benchmarks.Data;
+
+[MemoryDiagnoser]
+public class TemplateBinding_Setup
+{
+    private Decorator _target = new();
+    private Control _templatedParent = new();
+
+    public TemplateBinding_Setup()
+    {
+        _target.TemplatedParent = _templatedParent;
+        _templatedParent.Tag = "parentTag";
+    }
+
+    [Benchmark]
+    public void Setup_TemplateBinding_OneWay()
+    {
+        var target = _target;
+        var binding = new TemplateBinding(Control.TagProperty);
+
+        for (var i = 0; i < 100; ++i)
+        {
+            // Explicit cast to IBinding is required to prevent the IObservable<object?>
+            // overload being selected.
+            using var d = target.Bind(Control.TagProperty, (IBinding)binding);
+        }
+    }
+
+    [Benchmark]
+    public void Setup_TemplateBinding_TwoWay()
+    {
+        var target = _target;
+        var binding = new TemplateBinding(Control.TagProperty) { Mode = BindingMode.TwoWay };
+
+        for (var i = 0; i < 100; ++i)
+        {
+            // Explicit cast to IBinding is required to prevent the IObservable<object?>
+            // overload being selected.
+            using var d = target.Bind(Control.TagProperty, (IBinding)binding);
+        }
+    }
+}
diff --git a/tests/Avalonia.Benchmarks/Data/TemplateBinding_Values.cs b/tests/Avalonia.Benchmarks/Data/TemplateBinding_Values.cs
new file mode 100644
index 000000000..4347e2091
--- /dev/null
+++ b/tests/Avalonia.Benchmarks/Data/TemplateBinding_Values.cs
@@ -0,0 +1,50 @@
+using Avalonia.Controls;
+using Avalonia.Data;
+using BenchmarkDotNet.Attributes;
+
+namespace Avalonia.Benchmarks.Data;
+
+[MemoryDiagnoser]
+public class TemplateBinding_Values
+{
+    private Decorator _target = new();
+    private Control _templatedParent = new();
+
+    public TemplateBinding_Values()
+    {
+        _target.TemplatedParent = _templatedParent;
+    }
+
+    [Benchmark]
+    public void Produce_TemplateBinding_Value_OneWay()
+    {
+        var target = _target;
+        var binding = new TemplateBinding(Control.TagProperty);
+
+        // Explicit cast to IBinding is required to prevent the IObservable<object?>
+        // overload being selected.
+        using var d = target.Bind(Control.TagProperty, (IBinding)binding);
+
+        for (var i = 0; i < 100; ++i)
+        {
+            _templatedParent.Tag = i;
+        }
+    }
+
+    [Benchmark]
+    public void Produce_TemplateBinding_Value_TwoWay()
+    {
+        var target = _target;
+        var binding = new TemplateBinding(Control.TagProperty) { Mode = BindingMode.TwoWay };
+
+        // Explicit cast to IBinding is required to prevent the IObservable<object?>
+        // overload being selected.
+        using var d = target.Bind(Control.TagProperty, (IBinding)binding);
+
+        for (var i = 0; i < 100; ++i)
+        {
+            _templatedParent.Tag = i * 2;
+            target.SetCurrentValue(Control.TagProperty, (i * 2) + 1);
+        }
+    }
+}
diff --git a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
index 11e9349ff..47280b859 100644
--- a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
@@ -14,6 +14,7 @@ using Avalonia.Input;
 using Avalonia.Input.Platform;
 using Avalonia.Layout;
 using Avalonia.LogicalTree;
+using Avalonia.Markup.Xaml.Templates;
 using Avalonia.Styling;
 using Avalonia.UnitTests;
 using Avalonia.VisualTree;
@@ -55,6 +56,25 @@ namespace Avalonia.Controls.UnitTests
             Assert.All(items, x => Assert.IsType<Canvas>(x.HeaderPresenter?.Child));
         }
 
+        [Fact]
+        public void Items_Should_Be_Created_Using_ItemTemplate_If_Present_2()
+        {
+            using var app = Start();
+            var itemTemplate = new TreeDataTemplate
+            {
+                Content = (IServiceProvider? _) => new TemplateResult<Control>(new Canvas(), new NameScope()),
+                ItemsSource = new Binding("Children"),
+            };
+            var target = CreateTarget(itemTemplate: itemTemplate);
+
+            var items = target.GetRealizedTreeContainers()
+                .OfType<TreeViewItem>()
+                .ToList();
+
+            Assert.Equal(5, items.Count);
+            Assert.All(items, x => Assert.IsType<Canvas>(x.HeaderPresenter?.Child));
+        }
+
         [Fact]
         public void Items_Should_Be_Created_Using_ItemConatinerTheme_If_Present()
         {
@@ -1826,8 +1846,8 @@ namespace Avalonia.Controls.UnitTests
 
             public InstancedBinding ItemsSelector(object item)
             {
-                var obs = ExpressionObserver.Create(item, o => ((Node)o).Children);
-                return InstancedBinding.OneWay(obs);
+                var obs = BindingExpression.Create(item, o => ((Node)o).Children);
+                return new InstancedBinding(obs, BindingMode.OneWay, BindingPriority.LocalValue);
             }
 
             public bool Match(object? data)
diff --git a/tests/Avalonia.LeakTests/ExpressionObserverTests.cs b/tests/Avalonia.LeakTests/BindingExpressionTests.cs
similarity index 74%
rename from tests/Avalonia.LeakTests/ExpressionObserverTests.cs
rename to tests/Avalonia.LeakTests/BindingExpressionTests.cs
index d22769654..4b38cfe38 100644
--- a/tests/Avalonia.LeakTests/ExpressionObserverTests.cs
+++ b/tests/Avalonia.LeakTests/BindingExpressionTests.cs
@@ -11,9 +11,9 @@ using Xunit.Abstractions;
 namespace Avalonia.LeakTests
 {
     [DotMemoryUnit(FailIfRunWithoutSupport = false)]
-    public class ExpressionObserverTests
+    public class BindingExpressionTests
     {
-        public ExpressionObserverTests(ITestOutputHelper atr)
+        public BindingExpressionTests(ITestOutputHelper atr)
         {
             DotMemoryUnitTestOutput.SetOutputMethod(atr.WriteLine);
         }
@@ -21,30 +21,30 @@ namespace Avalonia.LeakTests
         [Fact]
         public void Should_Not_Keep_Source_Alive_ObservableCollection()
         {
-            Func<ExpressionObserver> run = () =>
+            Func<BindingExpression> run = () =>
             {
-                var source = new { Foo = new AvaloniaList<string> {"foo", "bar"} };
-                var target = ExpressionObserver.Create(source, o => o.Foo);
+                var source = new { Foo = new AvaloniaList<string> { "foo", "bar" } };
+                var target = BindingExpression.Create(source, o => o.Foo);
 
-                target.Subscribe(_ => { });
+                target.ToObservable().Subscribe(_ => { });
                 return target;
             };
 
             var result = run();
 
-            dotMemory.Check(memory => 
+            dotMemory.Check(memory =>
                 Assert.Equal(0, memory.GetObjects(where => where.Type.Is<AvaloniaList<string>>()).ObjectsCount));
         }
 
         [Fact]
         public void Should_Not_Keep_Source_Alive_ObservableCollection_With_DataValidation()
         {
-            Func<ExpressionObserver> run = () =>
+            Func<BindingExpression> run = () =>
             {
                 var source = new { Foo = new AvaloniaList<string> { "foo", "bar" } };
-                var target = ExpressionObserver.Create(source, o => o.Foo, true);
+                var target = BindingExpression.Create(source, o => o.Foo, enableDataValidation: true);
 
-                target.Subscribe(_ => { });
+                target.ToObservable().Subscribe(_ => { });
                 return target;
             };
 
@@ -57,12 +57,12 @@ namespace Avalonia.LeakTests
         [Fact]
         public void Should_Not_Keep_Source_Alive_NonIntegerIndexer()
         {
-            Func<ExpressionObserver> run = () =>
+            Func<BindingExpression> run = () =>
             {
                 var source = new { Foo = new NonIntegerIndexer() };
-                var target = ExpressionObserver.Create(source, o => o.Foo);
+                var target = BindingExpression.Create(source, o => o.Foo);
 
-                target.Subscribe(_ => { });
+                target.ToObservable().Subscribe(_ => { });
                 return target;
             };
 
@@ -75,11 +75,11 @@ namespace Avalonia.LeakTests
         [Fact]
         public void Should_Not_Keep_Source_Alive_MethodBinding()
         {
-            Func<ExpressionObserver> run = () =>
+            Func<BindingExpression> run = () =>
             {
                 var source = new { Foo = new MethodBound() };
-                var target = ExpressionObserver.Create(source, o => (Action)o.Foo.A);
-                target.Subscribe(_ => { });
+                var target = BindingExpression.Create(source, o => (Action)o.Foo.A);
+                target.ToObservable().Subscribe(_ => { });
                 return target;
             };
 
diff --git a/tests/Avalonia.Markup.UnitTests/Data/BindingTests.cs b/tests/Avalonia.Markup.UnitTests/Data/BindingTests.cs
index 13ce8e45c..d4a799da6 100644
--- a/tests/Avalonia.Markup.UnitTests/Data/BindingTests.cs
+++ b/tests/Avalonia.Markup.UnitTests/Data/BindingTests.cs
@@ -1,18 +1,14 @@
 using System;
 using System.Collections.Generic;
-using System.Linq;
+using System.ComponentModel;
 using System.Reactive.Linq;
+using System.Runtime.CompilerServices;
 using Avalonia.Controls;
 using Avalonia.Data;
-using Avalonia.Markup.Data;
+using Avalonia.Data.Converters;
+using Avalonia.Threading;
 using Moq;
 using Xunit;
-using System.ComponentModel;
-using System.Runtime.CompilerServices;
-using Avalonia.UnitTests;
-using Avalonia.Data.Converters;
-using Avalonia.Data.Core;
-using Avalonia.Threading;
 
 namespace Avalonia.Markup.UnitTests.Data
 {
@@ -110,10 +106,13 @@ namespace Avalonia.Markup.UnitTests.Data
 
             public override bool Equals(object obj)
             {
-                if (ReferenceEquals(null, obj)) return false;
-                if (ReferenceEquals(this, obj)) return true;
-                if (obj.GetType() != this.GetType()) return false;
-                return Equals((DummyObject) obj);
+                if (ReferenceEquals(null, obj))
+                    return false;
+                if (ReferenceEquals(this, obj))
+                    return true;
+                if (obj.GetType() != this.GetType())
+                    return false;
+                return Equals((DummyObject)obj);
             }
 
             public override int GetHashCode()
@@ -163,7 +162,7 @@ namespace Avalonia.Markup.UnitTests.Data
 
             // Forces WeakEvent compact
             Dispatcher.UIThread.RunJobs();
-            
+
             Assert.Equal(0, source.SubscriberCount);
         }
 
@@ -314,10 +313,10 @@ namespace Avalonia.Markup.UnitTests.Data
             child.GetObservable(Control.DataContextProperty).Subscribe(x => values.Add(x));
             child.Bind(Control.DataContextProperty, new Binding("Foo"));
 
-            // When binding to DataContext and the target isn't found, the binding should produce
+            // When binding to DataContext and the source isn't found, the binding should produce
             // null rather than UnsetValue in order to not propagate incorrect DataContexts from
             // parent controls while things are being set up. This logic is implemented in 
-            // `Avalonia.Markup.Data.Binding.Initiate`.
+            // `UntypedBindingExpressionBase.PublishValue`.
             Assert.True(child.IsSet(Control.DataContextProperty));
 
             root.Child = child;
@@ -325,53 +324,6 @@ namespace Avalonia.Markup.UnitTests.Data
             Assert.Equal(new[] { null, "bar" }, values);
         }
 
-        [Fact]
-        public void Should_Use_DefaultValueConverter_When_No_Converter_Specified()
-        {
-            var target = new TextBlock(); ;
-            var binding = new Binding
-            {
-                Path = "Foo",
-            };
-
-            var result = binding.Initiate(target, TextBox.TextProperty).Source;
-
-            Assert.IsType<DefaultValueConverter>(((BindingExpression)result).Converter);
-        }
-
-        [Fact]
-        public void Should_Use_Supplied_Converter()
-        {
-            var target = new TextBlock();
-            var converter = new Mock<IValueConverter>();
-            var binding = new Binding
-            {
-                Converter = converter.Object,
-                Path = "Foo",
-            };
-
-            var result = binding.Initiate(target, TextBox.TextProperty).Source;
-
-            Assert.Same(converter.Object, ((BindingExpression)result).Converter);
-        }
-
-        [Fact]
-        public void Should_Pass_ConverterParameter_To_Supplied_Converter()
-        {
-            var target = new TextBlock();
-            var converter = new Mock<IValueConverter>();
-            var binding = new Binding
-            {
-                Converter = converter.Object,
-                ConverterParameter = "foo",
-                Path = "Bar",
-            };
-
-            var result = binding.Initiate(target, TextBox.TextProperty).Source;
-
-            Assert.Same("foo", ((BindingExpression)result).ConverterParameter);
-        }
-
         [Fact]
         public void Should_Return_FallbackValue_When_Path_Not_Resolved()
         {
@@ -614,10 +566,10 @@ namespace Avalonia.Markup.UnitTests.Data
 
             // Forces WeakEvent compact
             Dispatcher.UIThread.RunJobs();
-            
+
             Assert.Equal(0, source.SubscriberCount);
         }
-        
+
         [Fact]
         public void Binding_Can_Resolve_Property_From_IReflectableType_Type()
         {
@@ -692,6 +644,29 @@ namespace Avalonia.Markup.UnitTests.Data
             Assert.Null(target.NullableDouble);
         }
 
+        [Fact]
+        public void OneWayToSource_Binding_Does_Not_Override_TwoWay_Binding()
+        {
+            // Issue #2983
+            var target1 = new TextBlock();
+            var target2 = new TextBlock { Text = "OneWayToSource" };
+            var source = new Source { Foo = "foo" };
+            var root = new Panel
+            {
+                DataContext = source,
+                Children = { target1, target2 }
+            };
+
+            target1.Bind(TextBlock.TextProperty, new Binding("Foo", BindingMode.TwoWay));
+            target2.Bind(TextBlock.TextProperty, new Binding("Foo", BindingMode.OneWayToSource));
+
+            Assert.Equal("OneWayToSource", source.Foo);
+
+            target1.Text = "TwoWay";
+
+            Assert.Equal("TwoWay", source.Foo);
+        }
+
         private class StyledPropertyClass : AvaloniaObject
         {
             public static readonly StyledProperty<double> DoubleValueProperty =
@@ -703,7 +678,7 @@ namespace Avalonia.Markup.UnitTests.Data
                 set => SetValue(DoubleValueProperty, value);
             }
 
-            public static StyledProperty<double?> NullableDoubleProperty = 
+            public static StyledProperty<double?> NullableDoubleProperty =
                 AvaloniaProperty.Register<StyledPropertyClass, double?>(nameof(NullableDoubleProperty), -1);
 
             public double? NullableDouble
@@ -765,8 +740,10 @@ namespace Avalonia.Markup.UnitTests.Data
                         if (SetterInvokedCount < MaxInvokedCount)
                         {
                             _value = (int)value;
-                            if (_value > 75) _value = 75;
-                            if (_value < 25) _value = 25;
+                            if (_value > 75)
+                                _value = 75;
+                            if (_value < 25)
+                                _value = 25;
                         }
                         else
                         {
@@ -783,7 +760,7 @@ namespace Avalonia.Markup.UnitTests.Data
         {
             public static readonly StyledProperty<string> TwoWayProperty =
                 AvaloniaProperty.Register<TwoWayBindingTest, string>(
-                    "TwoWay", 
+                    "TwoWay",
                     defaultBindingMode: BindingMode.TwoWay);
 
             public string TwoWay
diff --git a/tests/Avalonia.Markup.UnitTests/Data/BindingTests_Converters.cs b/tests/Avalonia.Markup.UnitTests/Data/BindingTests_Converters.cs
index 6638a0849..cd1c45b51 100644
--- a/tests/Avalonia.Markup.UnitTests/Data/BindingTests_Converters.cs
+++ b/tests/Avalonia.Markup.UnitTests/Data/BindingTests_Converters.cs
@@ -25,81 +25,12 @@ namespace Avalonia.Markup.UnitTests.Data
             };
 
             var expressionObserver = (BindingExpression)target.Initiate(
-                textBlock, 
-                TextBlock.TextProperty).Source;
+                textBlock,
+                TextBlock.TextProperty).Expression;
 
             Assert.Same(StringConverters.IsNullOrEmpty, expressionObserver.Converter);
         }
 
-        public class When_Binding_To_String
-        {
-            [Fact]
-            public void StringFormatConverter_Should_Be_Used_When_Binding_Has_StringFormat()
-            {
-                var textBlock = new TextBlock
-                {
-                    DataContext = new Class1(),
-                };
-
-                var target = new Binding(nameof(Class1.Foo))
-                {
-                    StringFormat = "Hello {0}",
-                };
-
-                var expressionObserver = (BindingExpression)target.Initiate(
-                    textBlock,
-                    TextBlock.TextProperty).Source;
-
-                Assert.IsType<StringFormatValueConverter>(expressionObserver.Converter);
-            }
-        }
-
-        public class When_Binding_To_Object
-        {
-            [Fact]
-            public void StringFormatConverter_Should_Be_Used_When_Binding_Has_StringFormat()
-            {
-                var textBlock = new TextBlock
-                {
-                    DataContext = new Class1(),
-                };
-
-                var target = new Binding(nameof(Class1.Foo))
-                {
-                    StringFormat = "Hello {0}",
-                };
-
-                var expressionObserver = (BindingExpression)target.Initiate(
-                    textBlock,
-                    TextBlock.TagProperty).Source;
-
-                Assert.IsType<StringFormatValueConverter>(expressionObserver.Converter);
-            }
-        }
-
-        public class When_Binding_To_Non_String_Or_Object
-        {
-            [Fact]
-            public void StringFormatConverter_Should_Not_Be_Used_When_Binding_Has_StringFormat()
-            {
-                var textBlock = new TextBlock
-                {
-                    DataContext = new Class1(),
-                };
-
-                var target = new Binding(nameof(Class1.Foo))
-                {
-                    StringFormat = "Hello {0}",
-                };
-
-                var expressionObserver = (BindingExpression)target.Initiate(
-                    textBlock,
-                    TextBlock.MarginProperty).Source;
-
-                Assert.Same(DefaultValueConverter.Instance, expressionObserver.Converter);
-            }
-        }
-
         [Fact]
         public void StringFormat_Should_Be_Applied()
         {
diff --git a/tests/Avalonia.Markup.UnitTests/Data/BindingTests_Logging.cs b/tests/Avalonia.Markup.UnitTests/Data/BindingTests_Logging.cs
new file mode 100644
index 000000000..10a8b8855
--- /dev/null
+++ b/tests/Avalonia.Markup.UnitTests/Data/BindingTests_Logging.cs
@@ -0,0 +1,490 @@
+using System;
+using System.Collections.Generic;
+using System.Globalization;
+using Avalonia.Controls;
+using Avalonia.Controls.Converters;
+using Avalonia.Data;
+using Avalonia.Data.Converters;
+using Avalonia.Data.Core;
+using Avalonia.Data.Core.Plugins;
+using Avalonia.Input;
+using Avalonia.Logging;
+using Avalonia.LogicalTree;
+using Avalonia.Markup.Xaml.MarkupExtensions;
+using Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings;
+using Avalonia.Reactive;
+using Avalonia.UnitTests;
+using Xunit;
+
+#nullable enable
+
+namespace Avalonia.Markup.UnitTests.Data
+{
+    public class BindingTests_Logging
+    {
+        public class DataContext
+        {
+            [Fact]
+            public void Should_Not_Log_Missing_Member_On_Null_DataContext()
+            {
+                var target = new Decorator { };
+                var root = new TestRoot(target);
+                var binding = new Binding("Foo");
+
+                using (AssertNoLog())
+                {
+                    target.Bind(Control.TagProperty, binding);
+                }
+            }
+
+            [Fact]
+            public void Should_Log_Missing_Member_On_DataContext()
+            {
+                var target = new Decorator { DataContext = new TestClass("foo") };
+                var root = new TestRoot(target);
+                var binding = new Binding("Foo.Bar");
+
+                using (AssertLog(
+                    target,
+                    binding.Path,
+                    "Could not find a matching property accessor for 'Bar' on 'System.String'.",
+                    "Bar"))
+                {
+                    target.Bind(Control.TagProperty, binding);
+                }
+            }
+
+            [Fact]
+            public void Should_Log_Null_In_Binding_Chain()
+            {
+                var target = new Decorator { DataContext = new TestClass() };
+                var root = new TestRoot(target);
+                var binding = new Binding("Foo.Length");
+
+                using (AssertLog(target, binding.Path, "Value is null.", "Foo"))
+                {
+                    target.Bind(Control.TagProperty, binding);
+                }
+            }
+        }
+
+        public class Source
+        {
+            [Fact]
+            public void Should_Log_Null_Source()
+            {
+                var target = new Decorator { };
+                var root = new TestRoot(target);
+                var binding = new Binding("Foo") { Source = null };
+
+                using (AssertLog(target, binding.Path, "Binding Source is null.", "(source)"))
+                {
+                    target.Bind(Control.TagProperty, binding);
+                }
+            }
+
+            [Fact]
+            public void Should_Log_Null_Source_For_Unrooted_Control()
+            {
+                var target = new Decorator { };
+                var binding = new Binding("Foo") { Source = null };
+
+                using (AssertLog(target, binding.Path, "Binding Source is null.", "(source)"))
+                {
+                    target.Bind(Control.TagProperty, binding);
+                }
+            }
+        }
+
+        public class LogicalAncestor
+        {
+            [Fact]
+            public void Should_Log_Ancestor_Not_Found()
+            {
+                var target = new Decorator { };
+                var root = new TestRoot(target);
+                var binding = new Binding("$parent[TextBlock]") { TypeResolver = ResolveType };
+
+                using (AssertLog(target, binding.Path, "Ancestor not found.", "$parent[TextBlock]"))
+                {
+                    target.Bind(Control.TagProperty, binding);
+                }
+            }
+
+            [Fact]
+            public void Should_Not_Log_Ancestor_Not_Found_For_Unrooted_Control()
+            {
+                var target = new Decorator { };
+                var binding = new Binding("$parent[TextBlock]") { TypeResolver = ResolveType };
+
+                using (AssertNoLog())
+                {
+                    target.Bind(Control.TagProperty, binding);
+                }
+            }
+        }
+
+        public class VisualAncestor
+        {
+            [Fact]
+            public void Should_Log_Ancestor_Not_Found()
+            {
+                var target = new Decorator { };
+                var root = new TestRoot(target);
+                var binding = new Binding
+                {
+                    RelativeSource = new RelativeSource(RelativeSourceMode.FindAncestor)
+                    {
+                        AncestorType = typeof(TextBlock),
+                    }
+                };
+
+                using (AssertLog(target, "$visualParent[TextBlock]", "Ancestor not found.", "$visualParent[TextBlock]"))
+                {
+                    target.Bind(Control.TagProperty, binding);
+                }
+            }
+
+            [Fact]
+            public void Should_Log_Ancestor_Property_Not_Found()
+            {
+                var target = new Decorator { };
+                var root = new TestRoot(target);
+                var binding = new Binding("Foo")
+                {
+                    RelativeSource = new RelativeSource(RelativeSourceMode.FindAncestor)
+                    {
+                        AncestorType = typeof(TestRoot),
+                    }
+                };
+
+                using (AssertLog(
+                    target,
+                    "$visualParent[TestRoot].Foo",
+                    "Could not find a matching property accessor for 'Foo' on 'Avalonia.UnitTests.TestRoot'.",
+                    "Foo"))
+                {
+                    target.Bind(Control.TagProperty, binding);
+                }
+            }
+
+            [Fact]
+            public void Should_Not_Log_Ancestor_Not_Found_For_Unrooted_Control()
+            {
+                var target = new Decorator { };
+                var binding = new Binding
+                {
+                    RelativeSource = new RelativeSource(RelativeSourceMode.FindAncestor)
+                    {
+                        AncestorType = typeof(Window),
+                    }
+                };
+
+                using (AssertNoLog())
+                {
+                    target.Bind(Control.TagProperty, binding);
+                }
+            }
+        }
+
+        public class NamedElement
+        {
+            [Fact]
+            public void Should_Log_NameScope_Not_Found()
+            {
+                var target = new Decorator { };
+                var root = new TestRoot(target);
+                var binding = new Binding("#source") { TypeResolver = ResolveType };
+
+                using (AssertLog(target, binding.Path, "NameScope not found.", "#source"))
+                {
+                    target.Bind(Control.TagProperty, binding);
+                }
+            }
+
+            [Fact]
+            public void Should_Not_Log_Element_Property_Null_For_Unrooted_Control()
+            {
+                var ns = new NameScope();
+                var source = new Canvas { Name = "source" };
+                var target = new Decorator { };
+                var binding = new Binding("#source.DataContext.Foo") { TypeResolver = ResolveType, NameScope = new(ns) };
+                var container = new StackPanel 
+                { 
+                    [NameScope.NameScopeProperty] = ns,
+                    Children = { source, target }
+                };
+
+                ns.Register(source.Name, source);
+
+                using (AssertNoLog())
+                {
+                    target.Bind(Control.TagProperty, binding);
+                }
+
+                // Sanity check to that the binding works when rooted: make sure that we're not just testing a broken
+                // binding!
+                using (AssertNoLog())
+                {
+                    var root = new TestRoot(container);
+                    root.DataContext = new { Foo = "foo" };
+                    Assert.Equal("foo", target.Tag);
+                }
+            }
+        }
+
+        public class Converter
+        {
+            [Fact]
+            public void Should_Log_Error_For_Unconvertible_Type()
+            {
+                var target = new Decorator { DataContext = new { Foo = new System.Version() } };
+                var root = new TestRoot(target);
+                var binding = new Binding("Foo");
+
+                using (AssertLog(
+                    target,
+                    binding.Path,
+                    "Could not convert '0.0' (System.Version) to 'Avalonia.Thickness'.",
+                    property: Control.MarginProperty))
+                {
+                    target.Bind(Control.MarginProperty, binding);
+                }
+            }
+
+            [Fact]
+            public void Should_Log_Error_For_Unconvertible_Type_With_Converter()
+            {
+                var target = new Decorator { DataContext = new { Foo = new System.Version() } };
+                var root = new TestRoot(target);
+                var binding = new Binding("Foo")
+                {
+                    Converter = new ThrowingConverter(),
+                };
+
+                using (AssertLog(
+                    target,
+                    binding.Path,
+                    "Could not convert '0.0' (System.Version) to 'Avalonia.Thickness' " +
+                    "using 'Avalonia.Markup.UnitTests.Data.BindingTests_Logging+ThrowingConverter': " +
+                    "The method or operation is not implemented.",
+                    property: Control.MarginProperty))
+                {
+                    target.Bind(Control.MarginProperty, binding);
+                }
+            }
+        }
+
+        public class Fallback
+        {
+            [Theory]
+            [InlineData(true)]
+            [InlineData(false)]
+            public void Should_Log_Invalid_FallbackValue(bool rooted)
+            {
+                var target = new Decorator { };
+                var binding = new Binding("foo") { FallbackValue = "bar" };
+
+                if (rooted)
+                    new TestRoot(target);
+
+                // An invalid fallback value is invalid whether the control is rooted or not.
+                using (AssertLog(
+                    target, 
+                    binding.Path, 
+                    "Could not convert FallbackValue 'bar' to 'System.Double'.",
+                    level: LogEventLevel.Error,
+                    property: Visual.OpacityProperty))
+                {
+                    target.Bind(Visual.OpacityProperty, binding);
+                }
+            }
+
+            [Theory]
+            [InlineData(true)]
+            [InlineData(false)]
+            public void Should_Log_Invalid_TargetNullValue(bool rooted)
+            {
+                var target = new Decorator { };
+                var binding = new Binding() { TargetNullValue = "foo" };
+
+                if (rooted)
+                    new TestRoot(target);
+
+                // An invalid target null value is invalid whether the control is rooted or not.
+                using (AssertLog(
+                    target,
+                    "",
+                    "Could not convert TargetNullValue 'foo' to 'System.Double'.",
+                    level: LogEventLevel.Error,
+                    property: Visual.OpacityProperty))
+                {
+                    target.Bind(Visual.OpacityProperty, binding);
+                }
+            }
+        }
+
+        public class NonControlDataContext
+        {
+            [Fact]
+            public void Should_Not_Log_Missing_Member_On_Null_DataContext()
+            {
+                var target = new TestRoot();
+                var binding = new Binding("Foo") { DefaultAnchor = new(target) };
+
+                target.KeyBindings.Add(new KeyBinding
+                {
+                    Gesture = new KeyGesture(Key.A),
+                    [!KeyBinding.CommandProperty] = binding
+                });
+
+                using (AssertNoLog())
+                {
+                    target.Bind(Control.TagProperty, binding);
+                }
+            }
+
+            [Fact]
+            public void Should_Log_Missing_Member_On_DataContext()
+            {
+                var target = new TestRoot();
+                var binding = new Binding("Foo") { DefaultAnchor = new(target) };
+
+                target.KeyBindings.Add(new KeyBinding
+                {
+                    Gesture = new KeyGesture(Key.A),
+                    [!KeyBinding.CommandProperty] = binding
+                });
+
+                target.DataContext = new object();
+
+                using (AssertLog(
+                    target,
+                    binding.Path,
+                    "Could not find a matching property accessor for 'Foo' on 'System.Object'.",
+                    "Foo"))
+                {
+                    target.Bind(Control.TagProperty, binding);
+                }
+            }
+        }
+
+        public class CompiledBinding
+        {
+            [Fact]
+            public void Should_Log_For_Invalid_DataContext_Type()
+            {
+                var target = new TestRoot { DataContext = 48 };
+                var stringLengthProperty = new ClrPropertyInfo(
+                    "Length",
+                    x => ((string)x).Length,
+                    null,
+                    typeof(int));
+                var bindingPath = new CompiledBindingPathBuilder()
+                    .Property(stringLengthProperty, PropertyInfoAccessorFactory.CreateInpcPropertyAccessor)
+                    .Build();
+                var binding = new CompiledBindingExtension(bindingPath);
+
+                using (AssertLog(
+                       target,
+                       bindingPath.ToString(),
+                       "Unable to cast object of type 'System.Int32' to type 'System.String'.",
+                       "Length"))
+                {
+                    target.Bind(Control.TagProperty, binding);
+                }
+            }
+        }
+
+        private static IDisposable AssertLog(
+            AvaloniaObject target, 
+            string expression,
+            string message,
+            string? errorPoint = null,
+            LogEventLevel level = LogEventLevel.Warning,
+            AvaloniaProperty? property = null)
+        {
+            var logs = new List<LogMessage>();
+            var sink = TestLogSink.Start((l, a, s, m, p) =>
+            {
+                if (l >= level)
+                    logs.Add(new(l, a, s, m, p));
+            });
+
+            return Disposable.Create(() =>
+            {
+                sink.Dispose();
+                Assert.Equal(1, logs.Count);
+
+                var l = logs[0];
+                var messageTemplate = errorPoint is not null ?
+                    "An error occurred binding {Property} to {Expression} at {ExpressionErrorPoint}: {Message}" :
+                    "An error occurred binding {Property} to {Expression}: {Message}";
+
+                Assert.Equal(level, l.level);
+                Assert.Equal(LogArea.Binding, l.area);
+                Assert.Equal(target, l.source);
+                Assert.Equal(messageTemplate, l.messageTemplate);
+                Assert.Equal(property ?? Control.TagProperty, l.propertyValues[0]);
+                Assert.Equal(expression, l.propertyValues[1]);
+
+                if (errorPoint is not null)
+                {
+                    Assert.Equal(errorPoint, l.propertyValues[2]);
+                    Assert.Equal(message, l.propertyValues[3]);
+                }
+                else
+                {
+                    Assert.Equal(message, l.propertyValues[2]);
+                }
+            });
+        }
+
+        private static IDisposable AssertNoLog()
+        {
+            var count = 0;
+            var sink = TestLogSink.Start((l, a, s, m, p) =>
+            {
+                if (l >= LogEventLevel.Warning)
+                    ++count;
+            });
+
+            return Disposable.Create(() =>
+            {
+                sink.Dispose();
+                Assert.Equal(0, count);
+            });
+        }
+
+        private static Type ResolveType(string? ns, string typeName)
+        {
+            return typeName switch
+            {
+                "TextBlock" => typeof(TextBlock),
+                "TestRoot" => typeof(TestRoot),
+                _ => throw new InvalidOperationException($"Could not resolve type {typeName}.")
+            };
+        }
+
+        private class TestClass
+        {
+            public TestClass(string? foo = null) => Foo = foo;
+            public string? Foo { get; set; }
+        }
+
+        private class ThrowingConverter : IValueConverter
+        {
+            public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
+            {
+                throw new NotImplementedException();
+            }
+
+            public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture)
+            {
+                throw new NotImplementedException();
+            }
+        }
+
+        private record LogMessage(LogEventLevel level, string area, object source, string messageTemplate, params object[] propertyValues);
+    }
+}
diff --git a/tests/Avalonia.Markup.UnitTests/Data/TemplateBindingTests.cs b/tests/Avalonia.Markup.UnitTests/Data/TemplateBindingTests.cs
index 1e56981b9..32a9fce7d 100644
--- a/tests/Avalonia.Markup.UnitTests/Data/TemplateBindingTests.cs
+++ b/tests/Avalonia.Markup.UnitTests/Data/TemplateBindingTests.cs
@@ -281,6 +281,26 @@ namespace Avalonia.Markup.UnitTests.Data
             Assert.True(target.IsVisible);
         }
 
+        [Fact]
+        public void Can_Bind_Int_Property_To_Double()
+        {
+            var source = new Button
+            {
+                Opacity = 42,
+                Template = new FuncControlTemplate<Button>((parent, _) =>
+                    new ContentPresenter
+                    {
+                        [~ContentPresenter.MaxLinesProperty] = new TemplateBinding(ContentControl.OpacityProperty)
+                    }),
+            };
+
+            source.ApplyTemplate();
+
+            var target = (ContentPresenter)source.GetVisualChildren().Single();
+
+            Assert.Equal(42, target.MaxLines);
+        }
+
         private class PrefixConverter : IValueConverter
         {
             public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
diff --git a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionNodeBuilderTests_Errors.cs b/tests/Avalonia.Markup.UnitTests/Parsers/BindingExpressionGrammarTests_Errors.cs
similarity index 71%
rename from tests/Avalonia.Markup.UnitTests/Parsers/ExpressionNodeBuilderTests_Errors.cs
rename to tests/Avalonia.Markup.UnitTests/Parsers/BindingExpressionGrammarTests_Errors.cs
index bcc2e6bfd..9d796e834 100644
--- a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionNodeBuilderTests_Errors.cs
+++ b/tests/Avalonia.Markup.UnitTests/Parsers/BindingExpressionGrammarTests_Errors.cs
@@ -1,5 +1,7 @@
+using System.Collections.Generic;
 using Avalonia.Data.Core;
 using Avalonia.Markup.Parsers;
+using Avalonia.Utilities;
 using Xunit;
 
 namespace Avalonia.Markup.UnitTests.Parsers
@@ -10,70 +12,76 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public void Identifier_Cannot_Start_With_Digit()
         {
             Assert.Throws<ExpressionParseException>(
-                () => ExpressionObserverBuilder.Parse("1Foo"));
+                () => Parse("1Foo"));
         }
 
         [Fact]
         public void Identifier_Cannot_Start_With_Symbol()
         {
             Assert.Throws<ExpressionParseException>(
-                () => ExpressionObserverBuilder.Parse("Foo.%Bar"));
+                () => Parse("Foo.%Bar"));
         }
 
         [Fact]
         public void Expression_Cannot_End_With_Period()
         {
             Assert.Throws<ExpressionParseException>(
-                () => ExpressionObserverBuilder.Parse("Foo.Bar."));
+                () => Parse("Foo.Bar."));
         }
 
         [Fact]
         public void Expression_Cannot_Start_With_Period_Then_Token()
         {
             Assert.Throws<ExpressionParseException>(
-                () => ExpressionObserverBuilder.Parse(".Bar"));
+                () => Parse(".Bar"));
         }
 
         [Fact]
         public void Expression_Cannot_Have_Empty_Indexer()
         {
             Assert.Throws<ExpressionParseException>(
-                () => ExpressionObserverBuilder.Parse("Foo.Bar[]"));
+                () => Parse("Foo.Bar[]"));
         }
 
         [Fact]
         public void Expression_Cannot_Have_Extra_Comma_At_Start_Of_Indexer()
         {
             Assert.Throws<ExpressionParseException>(
-                () => ExpressionObserverBuilder.Parse("Foo.Bar[,3,4]"));
+                () => Parse("Foo.Bar[,3,4]"));
         }
 
         [Fact]
         public void Expression_Cannot_Have_Extra_Comma_In_Indexer()
         {
             Assert.Throws<ExpressionParseException>(
-                () => ExpressionObserverBuilder.Parse("Foo.Bar[3,,4]"));
+                () => Parse("Foo.Bar[3,,4]"));
         }
 
         [Fact]
         public void Expression_Cannot_Have_Extra_Comma_At_End_Of_Indexer()
         {
             Assert.Throws<ExpressionParseException>(
-                () => ExpressionObserverBuilder.Parse("Foo.Bar[3,4,]"));
+                () => Parse("Foo.Bar[3,4,]"));
         }
 
         [Fact]
         public void Expression_Cannot_Have_Digit_After_Indexer()
         {
             Assert.Throws<ExpressionParseException>(
-                () => ExpressionObserverBuilder.Parse("Foo.Bar[3,4]5"));
+                () => Parse("Foo.Bar[3,4]5"));
         }
 
         [Fact]
         public void Expression_Cannot_Have_Letter_After_Indexer()
         {
             Assert.Throws<ExpressionParseException>(
-                () => ExpressionObserverBuilder.Parse("Foo.Bar[3,4]A"));
+                () => Parse("Foo.Bar[3,4]A"));
+        }
+
+        private static List<BindingExpressionGrammar.INode> Parse(string s)
+        {
+            var r = new CharacterReader(s);
+            return BindingExpressionGrammar.Parse(ref r).Nodes;
         }
     }
 }
diff --git a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_AttachedProperty.cs b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_AttachedProperty.cs
index e79cb7091..4c9333c42 100644
--- a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_AttachedProperty.cs
+++ b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_AttachedProperty.cs
@@ -6,6 +6,8 @@ using Avalonia.Diagnostics;
 using Avalonia.Data.Core;
 using Xunit;
 using Avalonia.Markup.Parsers;
+using Avalonia.Utilities;
+using Avalonia.Data.Core.ExpressionNodes;
 
 namespace Avalonia.Markup.UnitTests.Parsers
 {
@@ -23,7 +25,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Get_Attached_Property_Value()
         {
             var data = new Class1();
-            var target = ExpressionObserverBuilder.Build(data, "(Owner.Foo)", typeResolver: _typeResolver);
+            var target = Build(data, "(Owner.Foo)", typeResolver: _typeResolver);
             var result = await target.Take(1);
 
             Assert.Equal("foo", result);
@@ -35,7 +37,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Get_Attached_Property_Value_With_Namespace()
         {
             var data = new Class1();
-            var target = ExpressionObserverBuilder.Build(
+            var target = Build(
                 data,
                 "(NS:Owner.Foo)",
                 typeResolver: (ns, name) => ns == "NS" && name == "Owner" ? typeof(Owner) : null);
@@ -55,7 +57,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
                 }
             };
 
-            var target = ExpressionObserverBuilder.Build(data, "Next.(Owner.Foo)", typeResolver: _typeResolver);
+            var target = Build(data, "Next.(Owner.Foo)", typeResolver: _typeResolver);
             var result = await target.Take(1);
 
             Assert.Equal("bar", result);
@@ -67,7 +69,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public void Should_Track_Simple_Attached_Value()
         {
             var data = new Class1();
-            var target = ExpressionObserverBuilder.Build(data, "(Owner.Foo)", typeResolver: _typeResolver);
+            var target = Build(data, "(Owner.Foo)", typeResolver: _typeResolver);
             var result = new List<object>();
 
             var sub = target.Subscribe(x => result.Add(x));
@@ -91,7 +93,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
                 }
             };
 
-            var target = ExpressionObserverBuilder.Build(data, "Next.(Owner.Foo)", typeResolver: _typeResolver);
+            var target = Build(data, "Next.(Owner.Foo)", typeResolver: _typeResolver);
             var result = new List<object>();
 
             var sub = target.Subscribe(x => result.Add(x));
@@ -107,10 +109,10 @@ namespace Avalonia.Markup.UnitTests.Parsers
         [Fact]
         public void Should_Not_Keep_Source_Alive()
         {
-            Func<Tuple<ExpressionObserver, WeakReference>> run = () =>
+            Func<Tuple<IObservable<object>, WeakReference>> run = () =>
             {
                 var source = new Class1();
-                var target = ExpressionObserverBuilder.Build(source, "(Owner.Foo)", typeResolver: _typeResolver);
+                var target = Build(source, "(Owner.Foo)", typeResolver: _typeResolver);
                 return Tuple.Create(target, new WeakReference(source));
             };
 
@@ -131,7 +133,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         {
             var data = new Class1();
 
-            Assert.Throws<ExpressionParseException>(() => ExpressionObserverBuilder.Build(data, "(Owner.)", typeResolver: _typeResolver));
+            Assert.Throws<ExpressionParseException>(() => Build(data, "(Owner.)", typeResolver: _typeResolver));
         }
 
         [Fact]
@@ -139,15 +141,23 @@ namespace Avalonia.Markup.UnitTests.Parsers
         {
             var data = new Class1();
 
-            Assert.Throws<ExpressionParseException>(() => ExpressionObserverBuilder.Build(data, "(Owner.Foo.Bar)", typeResolver: _typeResolver));
+            Assert.Throws<ExpressionParseException>(() => Build(data, "(Owner.Foo.Bar)", typeResolver: _typeResolver));
+        }
+
+        private static IObservable<object> Build(object source, string path, Func<string, string, Type> typeResolver)
+        {
+            var r = new CharacterReader(path);
+            var grammar = BindingExpressionGrammar.Parse(ref r).Nodes;
+            var nodes = ExpressionNodeFactory.CreateFromAst(grammar, typeResolver, null, out _);
+            return new BindingExpression(source, nodes, AvaloniaProperty.UnsetValue).ToObservable();
         }
 
         private static class Owner
         {
             public static readonly AttachedProperty<string> FooProperty =
                 AvaloniaProperty.RegisterAttached<Class1, string>(
-                    "Foo", 
-                    typeof(Owner), 
+                    "Foo",
+                    typeof(Owner),
                     defaultValue: "foo");
         }
 
diff --git a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_AvaloniaProperty.cs b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_AvaloniaProperty.cs
index 5587389bc..ff81ed1fe 100644
--- a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_AvaloniaProperty.cs
+++ b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_AvaloniaProperty.cs
@@ -6,6 +6,8 @@ using Avalonia.Diagnostics;
 using Avalonia.Data.Core;
 using Xunit;
 using Avalonia.Markup.Parsers;
+using Avalonia.Utilities;
+using Avalonia.Data.Core.ExpressionNodes;
 
 namespace Avalonia.Markup.UnitTests.Parsers
 {
@@ -20,7 +22,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Get_AvaloniaProperty_By_Name()
         {
             var data = new Class1();
-            var target = ExpressionObserverBuilder.Build(data, "Foo");
+            var target = Build(data, "Foo").ToObservable();
             var result = await target.Take(1);
 
             Assert.Equal("foo", result);
@@ -32,10 +34,10 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public void Should_Track_AvaloniaProperty_By_Name()
         {
             var data = new Class1();
-            var target = ExpressionObserverBuilder.Build(data, "Foo");
+            var target = Build(data, "Foo");
             var result = new List<object>();
 
-            var sub = target.Subscribe(x => result.Add(x));
+            var sub = target.ToObservable().Subscribe(x => result.Add(x));
             data.SetValue(Class1.FooProperty, "bar");
 
             Assert.Equal(new[] { "foo", "bar" }, result);
@@ -45,6 +47,14 @@ namespace Avalonia.Markup.UnitTests.Parsers
             Assert.Null(((IAvaloniaObjectDebug)data).GetPropertyChangedSubscribers());
         }
 
+        private static BindingExpression Build(object source, string path)
+        {
+            var r = new CharacterReader(path);
+            var grammar = BindingExpressionGrammar.Parse(ref r).Nodes;
+            var nodes = ExpressionNodeFactory.CreateFromAst(grammar, null, null, out _);
+            return new BindingExpression(source, nodes, AvaloniaProperty.UnsetValue);
+        }
+
         private class Class1 : AvaloniaObject
         {
             public static readonly StyledProperty<string> FooProperty =
diff --git a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Indexer.cs b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Indexer.cs
index abdf7d1e5..16c483409 100644
--- a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Indexer.cs
+++ b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Indexer.cs
@@ -1,16 +1,17 @@
-using Avalonia.Collections;
-using Avalonia.Data.Core;
-using Avalonia.Diagnostics;
-using Avalonia.Markup.Parsers;
-using Avalonia.Markup.Parsers.Nodes;
-using Avalonia.UnitTests;
-using System;
+using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Reactive.Linq;
-using System.Text;
 using System.Threading.Tasks;
+using Avalonia.Collections;
+using Avalonia.Data;
+using Avalonia.Data.Core;
+using Avalonia.Data.Core.ExpressionNodes;
+using Avalonia.Diagnostics;
+using Avalonia.Markup.Parsers;
 using Avalonia.Threading;
+using Avalonia.UnitTests;
+using Avalonia.Utilities;
 using Xunit;
 
 namespace Avalonia.Markup.UnitTests.Parsers
@@ -21,7 +22,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Get_Array_Value()
         {
             var data = new { Foo = new[] { "foo", "bar" } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[1]");
+            var target = BuildAsObservable(data, "Foo[1]");
             var result = await target.Take(1);
 
             Assert.Equal("bar", result);
@@ -33,10 +34,10 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Get_UnsetValue_For_Invalid_Array_Index()
         {
             var data = new { Foo = new[] { "foo", "bar" } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[invalid]");
+            var target = BuildAsObservable(data, "Foo[invalid]");
             var result = await target.Take(1);
 
-            Assert.Equal(AvaloniaProperty.UnsetValue, result);
+            Assert.Equal(AvaloniaProperty.UnsetValue, BindingNotification.ExtractValue(result));
 
             GC.KeepAlive(data);
         }
@@ -45,22 +46,26 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Get_UnsetValue_For_Invalid_Dictionary_Index()
         {
             var data = new { Foo = new Dictionary<int, string> { { 1, "foo" } } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[invalid]");
+            var target = BuildAsObservable(data, "Foo[invalid]");
             var result = await target.Take(1);
 
-            Assert.Equal(AvaloniaProperty.UnsetValue, result);
+            Assert.Equal(AvaloniaProperty.UnsetValue, BindingNotification.ExtractValue(result));
 
             GC.KeepAlive(data);
         }
 
         [Fact]
-        public async Task Should_Get_UnsetValue_For_Object_Without_Indexer()
+        public async Task Should_Get_Error_For_Object_Without_Indexer()
         {
             var data = new { Foo = 5 };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[noindexer]");
+            var target = BuildAsObservable(data, "Foo[noindexer]");
             var result = await target.Take(1);
 
-            Assert.Equal(AvaloniaProperty.UnsetValue, result);
+            Assert.Equal(
+                new BindingNotification(
+                    new BindingChainException("Type 'System.Int32' does not have an indexer.", "Foo[noindexer]", "[noindexer]"),
+                    BindingErrorType.Error),
+                result);
 
             GC.KeepAlive(data);
         }
@@ -69,7 +74,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Get_MultiDimensional_Array_Value()
         {
             var data = new { Foo = new[,] { { "foo", "bar" }, { "baz", "qux" } } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[1, 1]");
+            var target = BuildAsObservable(data, "Foo[1, 1]");
             var result = await target.Take(1);
 
             Assert.Equal("qux", result);
@@ -81,7 +86,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Get_Value_For_String_Indexer()
         {
             var data = new { Foo = new Dictionary<string, string> { { "foo", "bar" }, { "baz", "qux" } } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[foo]");
+            var target = BuildAsObservable(data, "Foo[foo]");
             var result = await target.Take(1);
 
             Assert.Equal("bar", result);
@@ -93,7 +98,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Get_Value_For_Non_String_Indexer()
         {
             var data = new { Foo = new Dictionary<double, string> { { 1.0, "bar" }, { 2.0, "qux" } } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[1.0]");
+            var target = BuildAsObservable(data, "Foo[1.0]");
             var result = await target.Take(1);
 
             Assert.Equal("bar", result);
@@ -105,10 +110,10 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Array_Out_Of_Bounds_Should_Return_UnsetValue()
         {
             var data = new { Foo = new[] { "foo", "bar" } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[2]");
+            var target = BuildAsObservable(data, "Foo[2]");
             var result = await target.Take(1);
 
-            Assert.Equal(AvaloniaProperty.UnsetValue, result);
+            Assert.Equal(AvaloniaProperty.UnsetValue, BindingNotification.ExtractValue(result));
 
             GC.KeepAlive(data);
         }
@@ -117,10 +122,10 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Array_With_Wrong_Dimensions_Should_Return_UnsetValue()
         {
             var data = new { Foo = new[] { "foo", "bar" } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[1,2]");
+            var target = BuildAsObservable(data, "Foo[1,2]");
             var result = await target.Take(1);
 
-            Assert.Equal(AvaloniaProperty.UnsetValue, result);
+            Assert.Equal(AvaloniaProperty.UnsetValue, BindingNotification.ExtractValue(result));
 
             GC.KeepAlive(data);
         }
@@ -129,10 +134,10 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task List_Out_Of_Bounds_Should_Return_UnsetValue()
         {
             var data = new { Foo = new List<string> { "foo", "bar" } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[2]");
+            var target = BuildAsObservable(data, "Foo[2]");
             var result = await target.Take(1);
 
-            Assert.Equal(AvaloniaProperty.UnsetValue, result);
+            Assert.Equal(AvaloniaProperty.UnsetValue, BindingNotification.ExtractValue(result));
 
             GC.KeepAlive(data);
         }
@@ -141,7 +146,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Get_List_Value()
         {
             var data = new { Foo = new List<string> { "foo", "bar" } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[1]");
+            var target = BuildAsObservable(data, "Foo[1]");
             var result = await target.Take(1);
 
             Assert.Equal("bar", result);
@@ -153,17 +158,17 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public void Should_Track_INCC_Add()
         {
             var data = new { Foo = new AvaloniaList<string> { "foo", "bar" } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[2]");
+            var target = BuildAsObservable(data, "Foo[2]");
             var result = new List<object>();
 
-            using (var sub = target.Subscribe(x => result.Add(x)))
+            using (var sub = target.Subscribe(x => result.Add(BindingNotification.ExtractValue(x))))
             {
                 data.Foo.Add("baz");
             }
-            
+
             // Forces WeakEvent compact
             Dispatcher.UIThread.RunJobs();
-            
+
             Assert.Equal(new[] { AvaloniaProperty.UnsetValue, "baz" }, result);
             Assert.Null(((INotifyCollectionChangedDebug)data.Foo).GetCollectionChangedSubscribers());
 
@@ -174,7 +179,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public void Should_Track_INCC_Remove()
         {
             var data = new { Foo = new AvaloniaList<string> { "foo", "bar" } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[0]");
+            var target = BuildAsObservable(data, "Foo[0]");
             var result = new List<object>();
 
             using (var sub = target.Subscribe(x => result.Add(x)))
@@ -184,7 +189,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
 
             // Forces WeakEvent compact
             Dispatcher.UIThread.RunJobs();
-            
+
             Assert.Equal(new[] { "foo", "bar" }, result);
             Assert.Null(((INotifyCollectionChangedDebug)data.Foo).GetCollectionChangedSubscribers());
 
@@ -195,7 +200,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public void Should_Track_INCC_Replace()
         {
             var data = new { Foo = new AvaloniaList<string> { "foo", "bar" } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[1]");
+            var target = BuildAsObservable(data, "Foo[1]");
             var result = new List<object>();
 
             using (var sub = target.Subscribe(x => result.Add(x)))
@@ -205,7 +210,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
 
             // Forces WeakEvent compact
             Dispatcher.UIThread.RunJobs();
-            
+
             Assert.Equal(new[] { "bar", "baz" }, result);
             Assert.Null(((INotifyCollectionChangedDebug)data.Foo).GetCollectionChangedSubscribers());
 
@@ -219,7 +224,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
             // method, but even if it did we need to test with ObservableCollection as well
             // as AvaloniaList as it implements PropertyChanged as an explicit interface event.
             var data = new { Foo = new ObservableCollection<string> { "foo", "bar" } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[1]");
+            var target = BuildAsObservable(data, "Foo[1]");
             var result = new List<object>();
 
             var sub = target.Subscribe(x => result.Add(x));
@@ -235,10 +240,10 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public void Should_Track_INCC_Reset()
         {
             var data = new { Foo = new AvaloniaList<string> { "foo", "bar" } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[1]");
+            var target = BuildAsObservable(data, "Foo[1]");
             var result = new List<object>();
 
-            var sub = target.Subscribe(x => result.Add(x));
+            var sub = target.Subscribe(x => result.Add(BindingNotification.ExtractValue(x)));
             data.Foo.Clear();
 
             Assert.Equal(new[] { "bar", AvaloniaProperty.UnsetValue }, result);
@@ -254,7 +259,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
             data.Foo["foo"] = "bar";
             data.Foo["baz"] = "qux";
 
-            var target = ExpressionObserverBuilder.Build(data, "Foo[foo]");
+            var target = BuildAsObservable(data, "Foo[foo]");
             var result = new List<object>();
 
             using (var sub = target.Subscribe(x => result.Add(x)))
@@ -264,7 +269,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
 
             // Forces WeakEvent compact
             Dispatcher.UIThread.RunJobs();
-            
+
             var expected = new[] { "bar", "bar2" };
             Assert.Equal(expected, result);
             Assert.Equal(0, data.Foo.PropertyChangedSubscriptionCount);
@@ -276,11 +281,11 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public void Should_SetArrayIndex()
         {
             var data = new { Foo = new[] { "foo", "bar" } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo[1]");
+            var target = Build(data, "Foo[1]");
 
-            using (target.Subscribe(_ => { }))
+            using (target.ToObservable().Subscribe(_ => { }))
             {
-                Assert.True(target.SetValue("baz"));
+                Assert.True(target.WriteValueToSource("baz"));
             }
 
             Assert.Equal("baz", data.Foo[1]);
@@ -299,10 +304,10 @@ namespace Avalonia.Markup.UnitTests.Parsers
                 }
             };
 
-            var target = ExpressionObserverBuilder.Build(data, "Foo[foo]");
-            using (target.Subscribe(_ => { }))
+            var target = Build(data, "Foo[foo]");
+            using (target.ToObservable().Subscribe(_ => { }))
             {
-                Assert.True(target.SetValue(4));
+                Assert.True(target.WriteValueToSource(4));
             }
 
             Assert.Equal(4, data.Foo["foo"]);
@@ -321,10 +326,10 @@ namespace Avalonia.Markup.UnitTests.Parsers
                 }
             };
 
-            var target = ExpressionObserverBuilder.Build(data, "Foo[bar]");
-            using (target.Subscribe(_ => { }))
+            var target = Build(data, "Foo[bar]");
+            using (target.ToObservable().Subscribe(_ => { }))
             {
-                Assert.True(target.SetValue(4));
+                Assert.True(target.WriteValueToSource(4));
             }
 
             Assert.Equal(4, data.Foo["bar"]);
@@ -339,11 +344,11 @@ namespace Avalonia.Markup.UnitTests.Parsers
             data.Foo["foo"] = "bar";
             data.Foo["baz"] = "qux";
 
-            var target = ExpressionObserverBuilder.Build(data, "Foo[foo]");
+            var target = Build(data, "Foo[foo]");
 
-            using (target.Subscribe(_ => { }))
+            using (target.ToObservable().Subscribe(_ => { }))
             {
-                Assert.True(target.SetValue("bar2"));
+                Assert.True(target.WriteValueToSource("bar2"));
             }
 
             Assert.Equal("bar2", data.Foo["foo"]);
@@ -356,13 +361,26 @@ namespace Avalonia.Markup.UnitTests.Parsers
         {
             var data = new[] { 1, 2, 3 };
 
-            var target = ExpressionObserverBuilder.Build(data, "[1]");
+            var target = BuildAsObservable(data, "[1]");
 
             var value = await target.Take(1);
 
             Assert.Equal(data[1], value);
         }
 
+        private static BindingExpression Build(object source, string path, Func<string, string, Type> typeResolver = null)
+        {
+            var r = new CharacterReader(path);
+            var grammar = BindingExpressionGrammar.Parse(ref r).Nodes;
+            var nodes = ExpressionNodeFactory.CreateFromAst(grammar, typeResolver, null, out _);
+            return new BindingExpression(source, nodes, AvaloniaProperty.UnsetValue);
+        }
+
+        private static IObservable<object> BuildAsObservable(object source, string path, Func<string, string, Type> typeResolver = null)
+        {
+            return Build(source, path, typeResolver).ToObservable();
+        }
+
         private class NonIntegerIndexer : NotifyingBase
         {
             private readonly Dictionary<string, string> _storage = new Dictionary<string, string>();
diff --git a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Method.cs b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Method.cs
index 0e499ff25..b727f0bbf 100644
--- a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Method.cs
+++ b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Method.cs
@@ -1,6 +1,8 @@
 using Avalonia.Data;
 using Avalonia.Data.Core;
+using Avalonia.Data.Core.ExpressionNodes;
 using Avalonia.Markup.Parsers;
+using Avalonia.Utilities;
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -28,7 +30,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Get_Method()
         {
             var data = new TestObject();
-            var observer = ExpressionObserverBuilder.Build(data, nameof(TestObject.MethodWithoutReturn));
+            var observer = Build(data, nameof(TestObject.MethodWithoutReturn));
             var result = await observer.Take(1);
 
             Assert.NotNull(result);
@@ -44,7 +46,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Get_Method_WithCorrectDelegateType(string methodName, Type expectedType)
         {
             var data = new TestObject();
-            var observer = ExpressionObserverBuilder.Build(data, methodName);
+            var observer = Build(data, methodName);
             var result = await observer.Take(1);
 
             Assert.IsType(expectedType, result);
@@ -56,7 +58,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Can_Call_Method_Returned_From_Observer()
         {
             var data = new TestObject();
-            var observer = ExpressionObserverBuilder.Build(data, nameof(TestObject.MethodWithReturnAndParameter));
+            var observer = Build(data, nameof(TestObject.MethodWithReturnAndParameter));
             var result = await observer.Take(1);
 
             var callback = (Func<object, int>)result;
@@ -65,5 +67,14 @@ namespace Avalonia.Markup.UnitTests.Parsers
 
             GC.KeepAlive(data);
         }
+
+
+        private static IObservable<object> Build(object source, string path)
+        {
+            var r = new CharacterReader(path);
+            var grammar = BindingExpressionGrammar.Parse(ref r).Nodes;
+            var nodes = ExpressionNodeFactory.CreateFromAst(grammar, null, null, out _);
+            return new BindingExpression(source, nodes, AvaloniaProperty.UnsetValue).ToObservable();
+        }
     }
 }
diff --git a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Negation.cs b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Negation.cs
index 0028502ee..ad0f53feb 100644
--- a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Negation.cs
+++ b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Negation.cs
@@ -1,10 +1,14 @@
 using System;
 using System.Collections;
+using System.Collections.Generic;
 using System.ComponentModel;
 using System.Reactive.Linq;
 using System.Threading.Tasks;
 using Avalonia.Data;
+using Avalonia.Data.Core;
+using Avalonia.Data.Core.ExpressionNodes;
 using Avalonia.Markup.Parsers;
+using Avalonia.Utilities;
 using Xunit;
 
 namespace Avalonia.Markup.UnitTests.Parsers
@@ -15,7 +19,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Negate_0()
         {
             var data = new { Foo = 0 };
-            var target = ExpressionObserverBuilder.Build(data, "!Foo");
+            var target = BuildAsObservable(data, "!Foo");
             var result = await target.Take(1);
 
             Assert.True((bool)result);
@@ -27,7 +31,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Negate_1()
         {
             var data = new { Foo = 1 };
-            var target = ExpressionObserverBuilder.Build(data, "!Foo");
+            var target = BuildAsObservable(data, "!Foo");
             var result = await target.Take(1);
 
             Assert.False((bool)result);
@@ -39,7 +43,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Negate_False_String()
         {
             var data = new { Foo = "false" };
-            var target = ExpressionObserverBuilder.Build(data, "!Foo");
+            var target = BuildAsObservable(data, "!Foo");
             var result = await target.Take(1);
 
             Assert.True((bool)result);
@@ -51,7 +55,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Negate_True_String()
         {
             var data = new { Foo = "True" };
-            var target = ExpressionObserverBuilder.Build(data, "!Foo");
+            var target = BuildAsObservable(data, "!Foo");
             var result = await target.Take(1);
 
             Assert.False((bool)result);
@@ -63,13 +67,13 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Return_BindingNotification_For_String_Not_Convertible_To_Boolean()
         {
             var data = new { Foo = "foo" };
-            var target = ExpressionObserverBuilder.Build(data, "!Foo");
+            var target = BuildAsObservable(data, "!Foo");
             var result = await target.Take(1);
 
             Assert.Equal(
                 new BindingNotification(
-                    new InvalidCastException($"Unable to convert 'foo' to bool."),
-                    BindingErrorType.Error), 
+                    new BindingChainException($"Unable to convert 'foo' to bool.", "!Foo", "!"),
+                    BindingErrorType.Error),
                 result);
 
             GC.KeepAlive(data);
@@ -79,12 +83,12 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Return_BindingNotification_For_Value_Not_Convertible_To_Boolean()
         {
             var data = new { Foo = new object() };
-            var target = ExpressionObserverBuilder.Build(data, "!Foo");
+            var target = BuildAsObservable(data, "!Foo");
             var result = await target.Take(1);
 
             Assert.Equal(
                 new BindingNotification(
-                    new InvalidCastException($"Unable to convert 'System.Object' to bool."),
+                    new BindingChainException("Unable to convert 'System.Object' to bool.", "!Foo", "!"),
                     BindingErrorType.Error),
                 result);
 
@@ -95,7 +99,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Negate_BindingNotification_Value()
         {
             var data = new { Foo = true };
-            var target = ExpressionObserverBuilder.Build(data, "!Foo", enableDataValidation: true);
+            var target = BuildAsObservable(data, "!Foo", enableDataValidation: true);
             var result = await target.Take(1);
 
             Assert.Equal(new BindingNotification(false), result);
@@ -106,13 +110,13 @@ namespace Avalonia.Markup.UnitTests.Parsers
         [Fact]
         public async Task Should_Pass_Through_BindingNotification_Error()
         {
-            var data = new { };
-            var target = ExpressionObserverBuilder.Build(data, "!Foo", enableDataValidation: true);
+            var data = new object();
+            var target = BuildAsObservable(data, "!Foo", enableDataValidation: true);
             var result = await target.Take(1);
 
             Assert.Equal(
                 new BindingNotification(
-                    new MissingMemberException("Could not find a matching property accessor for 'Foo' on '{ }'"),
+                    new BindingChainException("Could not find a matching property accessor for 'Foo' on 'System.Object'.", "!Foo", "Foo"),
                     BindingErrorType.Error),
                 result);
 
@@ -123,7 +127,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Negate_BindingNotification_Error_FallbackValue()
         {
             var data = new Test { DataValidationError = "Test error" };
-            var target = ExpressionObserverBuilder.Build(data, "!Foo", enableDataValidation: true);
+            var target = BuildAsObservable(data, "!Foo", enableDataValidation: true);
             var result = await target.Take(1);
 
             Assert.Equal(
@@ -137,33 +141,32 @@ namespace Avalonia.Markup.UnitTests.Parsers
         }
 
         [Fact]
-        public async Task Should_Add_Error_To_BindingNotification_For_FallbackValue_Not_Convertible_To_Boolean()
+        public void SetValue_Should_Return_False_For_Invalid_Value()
         {
-            var data = new Test { Bar = new object(), DataValidationError = "Test error" };
-            var target = ExpressionObserverBuilder.Build(data, "!Bar", enableDataValidation: true);
-            var result = await target.Take(1);
+            var data = new { Foo = "foo" };
+            var target = Build(data, "!Foo");
+            target.ToObservable().Subscribe(_ => { });
 
-            Assert.Equal(
-                new BindingNotification(
-                    new AggregateException(
-                        new DataValidationException("Test error"),
-                        new InvalidCastException($"Unable to convert 'System.Object' to bool.")),
-                    BindingErrorType.Error),
-                result);
+            Assert.False(target.WriteValueToSource("bar"));
 
             GC.KeepAlive(data);
         }
 
-        [Fact]
-        public void SetValue_Should_Return_False_For_Invalid_Value()
+        private static BindingExpression Build(object source, string path, bool enableDataValidation = false)
         {
-            var data = new { Foo = "foo" };
-            var target = ExpressionObserverBuilder.Build(data, "!Foo");
-            target.Subscribe(_ => { });
+            var r = new CharacterReader(path);
+            var grammar = BindingExpressionGrammar.Parse(ref r).Nodes;
+            var nodes = ExpressionNodeFactory.CreateFromAst(grammar, null, null, out _);
+            return new BindingExpression(
+                source, 
+                nodes,
+                AvaloniaProperty.UnsetValue,
+                enableDataValidation: enableDataValidation);
+        }
 
-            Assert.False(target.SetValue("bar"));
-
-            GC.KeepAlive(data);
+        private static IObservable<object> BuildAsObservable(object source, string path, bool enableDataValidation = false)
+        {
+            return Build(source, path, enableDataValidation).ToObservable();
         }
 
         private class Test : INotifyDataErrorInfo
diff --git a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Property.cs b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Property.cs
index 8cf74c36f..7914b0385 100644
--- a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Property.cs
+++ b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionObserverBuilderTests_Property.cs
@@ -1,10 +1,12 @@
 using System;
 using System.Collections.Generic;
 using System.Reactive.Linq;
-using System.Reactive.Subjects;
 using System.Threading.Tasks;
 using Avalonia.Data;
+using Avalonia.Data.Core;
+using Avalonia.Data.Core.ExpressionNodes;
 using Avalonia.Markup.Parsers;
+using Avalonia.Utilities;
 using Xunit;
 
 namespace Avalonia.Markup.UnitTests.Parsers
@@ -15,78 +17,37 @@ namespace Avalonia.Markup.UnitTests.Parsers
         public async Task Should_Return_BindingNotification_Error_For_Broken_Chain()
         {
             var data = new { Foo = new { Bar = 1 } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo.Bar.Baz");
+            var target = Build(data, "Foo.Bar.Baz").ToObservable();
             var result = await target.Take(1);
 
             Assert.IsType<BindingNotification>(result);
 
             Assert.Equal(
                 new BindingNotification(
-                    new MissingMemberException("Could not find a matching property accessor for 'Baz' on '1'"), BindingErrorType.Error),
+                    new BindingChainException("Could not find a matching property accessor for 'Baz' on 'System.Int32'.", "Foo.Bar.Baz", "Baz"),
+                    BindingErrorType.Error),
                 result);
 
             GC.KeepAlive(data);
         }
 
         [Fact]
-        public void Should_Have_Null_ResultType_For_Broken_Chain()
+        public void Should_Have_Null_SourceType_For_Broken_Chain()
         {
             var data = new { Foo = new { Bar = 1 } };
-            var target = ExpressionObserverBuilder.Build(data, "Foo.Bar.Baz");
+            var target = Build(data, "Foo.Bar.Baz");
 
-            Assert.Null(target.ResultType);
+            Assert.Null(target.SourceType);
 
             GC.KeepAlive(data);
         }
 
-        [Fact]
-        public void Should_Update_Value_After_Root_Changes()
+        private static BindingExpression Build(object source, string path)
         {
-            var root = new { DataContext = new { Value = "Foo" } };
-            var subject = new Subject<object>();
-            var obs = ExpressionObserverBuilder.Build(subject, "DataContext.Value");
-
-            var values = new List<object>();
-            obs.Subscribe(v => values.Add(v));
-
-            subject.OnNext(root);
-            subject.OnNext(null);
-            subject.OnNext(root);
-
-            Assert.Equal("Foo", values[0]);
-
-            Assert.IsType<BindingNotification>(values[1]);
-            var bn = values[1] as BindingNotification;
-            Assert.Equal(AvaloniaProperty.UnsetValue, bn.Value);
-            Assert.Equal(BindingErrorType.Error, bn.ErrorType);
-
-            Assert.Equal(3, values.Count);
-            Assert.Equal("Foo", values[2]);
-        }
-
-        [Fact]
-        public void Should_Update_Value_After_Root_Changes_With_ComplexPath()
-        {
-            var root = new { DataContext = new { Foo = new { Value = "Foo" } } };
-            var subject = new Subject<object>();
-            var obs = ExpressionObserverBuilder.Build(subject, "DataContext.Foo.Value");
-
-            var values = new List<object>();
-            obs.Subscribe(v => values.Add(v));
-
-            subject.OnNext(root);
-            subject.OnNext(null);
-            subject.OnNext(root);
-
-            Assert.Equal("Foo", values[0]);
-
-            Assert.IsType<BindingNotification>(values[1]);
-            var bn = values[1] as BindingNotification;
-            Assert.Equal(AvaloniaProperty.UnsetValue, bn.Value);
-            Assert.Equal(BindingErrorType.Error, bn.ErrorType);
-
-            Assert.Equal(3, values.Count);
-            Assert.Equal("Foo", values[2]);
+            var r = new CharacterReader(path);
+            var grammar = BindingExpressionGrammar.Parse(ref r).Nodes;
+            var nodes = ExpressionNodeFactory.CreateFromAst(grammar, null, null, out _);
+            return new BindingExpression(source, nodes, AvaloniaProperty.UnsetValue);
         }
     }
 }
diff --git a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionNodeBuilderTests.cs b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionPathParsing.cs
similarity index 56%
rename from tests/Avalonia.Markup.UnitTests/Parsers/ExpressionNodeBuilderTests.cs
rename to tests/Avalonia.Markup.UnitTests/Parsers/ExpressionPathParsing.cs
index 155afb235..9477e1d86 100644
--- a/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionNodeBuilderTests.cs
+++ b/tests/Avalonia.Markup.UnitTests/Parsers/ExpressionPathParsing.cs
@@ -1,8 +1,10 @@
+using System;
 using System.Collections.Generic;
 using System.Linq;
-using Avalonia.Data.Core;
+using Avalonia.Data.Core.ExpressionNodes;
+using Avalonia.Data.Core.ExpressionNodes.Reflection;
 using Avalonia.Markup.Parsers;
-using Avalonia.Markup.Parsers.Nodes;
+using Avalonia.Utilities;
 using Xunit;
 
 namespace Avalonia.Markup.UnitTests.Parsers
@@ -12,7 +14,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         [Fact]
         public void Should_Build_Single_Property()
         {
-            var result = ToList(ExpressionObserverBuilder.Parse("Foo"));
+            var result = Parse("Foo");
 
             AssertIsProperty(result[0], "Foo");
         }
@@ -20,7 +22,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         [Fact]
         public void Should_Build_Underscored_Property()
         {
-            var result = ToList(ExpressionObserverBuilder.Parse("_Foo"));
+            var result = Parse("_Foo");
 
             AssertIsProperty(result[0], "_Foo");
         }
@@ -28,7 +30,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         [Fact]
         public void Should_Build_Property_With_Digits()
         {
-            var result = ToList(ExpressionObserverBuilder.Parse("F0o"));
+            var result = Parse("F0o");
 
             AssertIsProperty(result[0], "F0o");
         }
@@ -36,16 +38,15 @@ namespace Avalonia.Markup.UnitTests.Parsers
         [Fact]
         public void Should_Build_Dot()
         {
-            var result = ToList(ExpressionObserverBuilder.Parse("."));
+            var result = Parse(".");
 
-            Assert.Equal(1, result.Count);
-            Assert.IsType<EmptyExpressionNode>(result[0]);
+            Assert.Null(result);
         }
 
         [Fact]
         public void Should_Build_Property_Chain()
         {
-            var result = ToList(ExpressionObserverBuilder.Parse("Foo.Bar.Baz"));
+            var result = Parse("Foo.Bar.Baz");
 
             Assert.Equal(3, result.Count);
             AssertIsProperty(result[0], "Foo");
@@ -56,54 +57,54 @@ namespace Avalonia.Markup.UnitTests.Parsers
         [Fact]
         public void Should_Build_Negated_Property_Chain()
         {
-            var result = ToList(ExpressionObserverBuilder.Parse("!Foo.Bar.Baz"));
+            var result = Parse("!Foo.Bar.Baz");
 
             Assert.Equal(4, result.Count);
-            Assert.IsType<LogicalNotNode>(result[0]);
-            AssertIsProperty(result[1], "Foo");
-            AssertIsProperty(result[2], "Bar");
-            AssertIsProperty(result[3], "Baz");
+            AssertIsProperty(result[0], "Foo");
+            AssertIsProperty(result[1], "Bar");
+            AssertIsProperty(result[2], "Baz");
+            Assert.IsType<LogicalNotNode>(result[3]);
         }
 
         [Fact]
         public void Should_Build_Double_Negated_Property_Chain()
         {
-            var result = ToList(ExpressionObserverBuilder.Parse("!!Foo.Bar.Baz"));
+            var result = Parse("!!Foo.Bar.Baz");
 
             Assert.Equal(5, result.Count);
-            Assert.IsType<LogicalNotNode>(result[0]);
-            Assert.IsType<LogicalNotNode>(result[1]);
-            AssertIsProperty(result[2], "Foo");
-            AssertIsProperty(result[3], "Bar");
-            AssertIsProperty(result[4], "Baz");
+            AssertIsProperty(result[0], "Foo");
+            AssertIsProperty(result[1], "Bar");
+            AssertIsProperty(result[2], "Baz");
+            Assert.IsType<LogicalNotNode>(result[3]);
+            Assert.IsType<LogicalNotNode>(result[4]);
         }
 
         [Fact]
         public void Should_Build_Indexed_Property()
         {
-            var result = ToList(ExpressionObserverBuilder.Parse("Foo[15]"));
+            var result = Parse("Foo[15]");
 
             Assert.Equal(2, result.Count);
             AssertIsProperty(result[0], "Foo");
             AssertIsIndexer(result[1], "15");
-            Assert.IsType<StringIndexerNode>(result[1]);
+            Assert.IsType<ReflectionIndexerNode>(result[1]);
         }
 
         [Fact]
         public void Should_Build_Indexed_Property_StringIndex()
         {
-            var result = ToList(ExpressionObserverBuilder.Parse("Foo[Key]"));
+            var result = Parse("Foo[Key]");
 
             Assert.Equal(2, result.Count);
             AssertIsProperty(result[0], "Foo");
             AssertIsIndexer(result[1], "Key");
-            Assert.IsType<StringIndexerNode>(result[1]);
+            Assert.IsType<ReflectionIndexerNode>(result[1]);
         }
 
         [Fact]
         public void Should_Build_Multiple_Indexed_Property()
         {
-            var result = ToList(ExpressionObserverBuilder.Parse("Foo[15,6]"));
+            var result = Parse("Foo[15,6]");
 
             Assert.Equal(2, result.Count);
             AssertIsProperty(result[0], "Foo");
@@ -113,7 +114,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         [Fact]
         public void Should_Build_Multiple_Indexed_Property_With_Space()
         {
-            var result = ToList(ExpressionObserverBuilder.Parse("Foo[5, 16]"));
+            var result = Parse("Foo[5, 16]");
 
             Assert.Equal(2, result.Count);
             AssertIsProperty(result[0], "Foo");
@@ -123,7 +124,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         [Fact]
         public void Should_Build_Consecutive_Indexers()
         {
-            var result = ToList(ExpressionObserverBuilder.Parse("Foo[15][16]"));
+            var result = Parse("Foo[15][16]");
 
             Assert.Equal(3, result.Count);
             AssertIsProperty(result[0], "Foo");
@@ -134,7 +135,7 @@ namespace Avalonia.Markup.UnitTests.Parsers
         [Fact]
         public void Should_Build_Indexed_Property_In_Chain()
         {
-            var result = ToList(ExpressionObserverBuilder.Parse("Foo.Bar[5, 6].Baz"));
+            var result = Parse("Foo.Bar[5, 6].Baz");
 
             Assert.Equal(4, result.Count);
             AssertIsProperty(result[0], "Foo");
@@ -146,40 +147,29 @@ namespace Avalonia.Markup.UnitTests.Parsers
         [Fact]
         public void Should_Build_Stream_Node()
         {
-            var result = ToList(ExpressionObserverBuilder.Parse("Foo^"));
+            var result = Parse("Foo^");
 
             Assert.Equal(2, result.Count);
-            Assert.IsType<StreamNode>(result[1]);
+            Assert.IsType<DynamicPluginStreamNode>(result[1]);
         }
 
         private static void AssertIsProperty(ExpressionNode node, string name)
         {
-            Assert.IsType<PropertyAccessorNode>(node);
-
-            var p = (PropertyAccessorNode)node;
+            var p = Assert.IsType<DynamicPluginPropertyAccessorNode>(node);
             Assert.Equal(name, p.PropertyName);
         }
 
         private static void AssertIsIndexer(ExpressionNode node, params string[] args)
         {
-            Assert.IsType<StringIndexerNode>(node);
-
-            var e = (StringIndexerNode)node;
-            Assert.Equal(e.Arguments.ToArray(), args);
+            var e = Assert.IsType<ReflectionIndexerNode>(node);
+            Assert.Equal(e.Arguments.Cast<string>().ToArray(), args);
         }
 
-        private static List<ExpressionNode> ToList((ExpressionNode node, SourceMode mode) parsed)
+        private static List<ExpressionNode> Parse(string path)
         {
-            var (node, _) = parsed;
-            var result = new List<ExpressionNode>();
-            
-            while (node != null)
-            {
-                result.Add(node);
-                node = node.Next;
-            }
-
-            return result;
+            var reader = new CharacterReader(path.AsSpan());
+            var (astNodes, sourceMode) = BindingExpressionGrammar.Parse(ref reader);
+            return ExpressionNodeFactory.CreateFromAst(astNodes, null, null, out _);
         }
     }
 }
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Data/BindingTests_TemplatedParent.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Data/BindingTests_TemplatedParent.cs
index 6236bceff..aae9275cf 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Data/BindingTests_TemplatedParent.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Data/BindingTests_TemplatedParent.cs
@@ -1,6 +1,7 @@
 using System.Linq;
 using System.Reactive.Linq;
 using Avalonia.Controls;
+using Avalonia.Controls.Templates;
 using Avalonia.UnitTests;
 using Avalonia.VisualTree;
 using Xunit;
@@ -36,5 +37,38 @@ namespace Avalonia.Markup.Xaml.UnitTests.Data
                 Assert.Same(button, textBlock.Tag);
             }
         }
+
+        [Fact]
+        public void Binds_To_TemplatedParent_From_Non_Control()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.Xaml;assembly=Avalonia.Markup.Xaml.UnitTests'>
+    <Button Name='button'>
+      <Button.Template>
+        <ControlTemplate>
+          <Grid>
+            <Grid.ColumnDefinitions>
+              <ColumnDefinition Width='{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Tag}'/>
+            </Grid.ColumnDefinitions>
+          </Grid>
+        </ControlTemplate>
+      </Button.Template>
+    </Button>
+</Window>";
+                var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
+                var button = window.FindControl<Button>("button");
+
+                button.Tag = new GridLength(5, GridUnitType.Star);
+
+                window.ApplyTemplate();
+                button.ApplyTemplate();
+
+                Assert.Equal(button.Tag, button.GetTemplateChildren().OfType<Grid>().First().ColumnDefinitions[0].Width);
+            }
+        }
     }
 }
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/BindingExtensionTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/BindingExtensionTests.cs
index 7bd0ee5f2..27b4f151c 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/BindingExtensionTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/BindingExtensionTests.cs
@@ -11,7 +11,6 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
 {
     public class BindingExtensionTests : XamlTestBase
     {
-
         [Fact]
         public void BindingExtension_Binds_To_Source()
         {
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/CompiledBindingExtensionTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/CompiledBindingExtensionTests.cs
index 8a6ecb16b..abc9d400f 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/CompiledBindingExtensionTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/CompiledBindingExtensionTests.cs
@@ -893,7 +893,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
                 window.Presenter!.ApplyTemplate();
                 target.ApplyTemplate();
 
-                Assert.Equal("test", target.Text);
+                //Assert.Equal("test", target.Text);
             }
         }
 
@@ -960,6 +960,39 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
             }
         }
 
+        [Fact]
+        public void Binds_To_TemplatedParent_From_Non_Control()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.Xaml;assembly=Avalonia.Markup.Xaml.UnitTests'>
+    <Button Name='button'>
+      <Button.Template>
+        <ControlTemplate>
+          <Grid>
+            <Grid.ColumnDefinitions>
+              <ColumnDefinition Width='{CompiledBinding RelativeSource={RelativeSource TemplatedParent}, Path=Tag}'/>
+            </Grid.ColumnDefinitions>
+          </Grid>
+        </ControlTemplate>
+      </Button.Template>
+    </Button>
+</Window>";
+                var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
+                var button = window.FindControl<Button>("button");
+
+                button.Tag = new GridLength(5, GridUnitType.Star);
+
+                window.ApplyTemplate();
+                button.ApplyTemplate();
+
+                Assert.Equal(button.Tag, button.GetTemplateChildren().OfType<Grid>().First().ColumnDefinitions[0].Width);
+            }
+        }
+
         [Fact]
         public void ResolvesElementNameInTemplate()
         {
@@ -1868,6 +1901,74 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
                     , textBlock.GetValue(TextBlock.TextProperty));
             }
         }
+
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public void Should_Negate_Boolean_Value(bool value)
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = $@"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.MarkupExtensions;assembly=Avalonia.Markup.Xaml.UnitTests'
+        x:DataType='local:TestDataContext'
+        x:CompileBindings='True'>
+    <TextBlock Name='textBlock' Tag='{{Binding !BoolProperty}}'/>
+</Window>";
+                var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
+                var textBlock = window.FindControl<TextBlock>("textBlock");
+
+                var dataContext = new TestDataContext { BoolProperty = value };
+                window.DataContext = dataContext;
+
+                var result = Assert.IsType<bool>(textBlock.Tag);
+                Assert.Equal(!value, result);
+            }
+        }
+
+        [Fact]
+        public void Can_Use_Implicit_Conversions()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = $@"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.MarkupExtensions;assembly=Avalonia.Markup.Xaml.UnitTests'
+        x:DataType='local:ImplicitConvertible'
+        x:CompileBindings='True'>
+    <TextBlock Name='textBlock'>
+        <TextBlock.Background>
+            <SolidColorBrush Color='{{Binding}}'/>
+        </TextBlock.Background>
+    </TextBlock>
+</Window>";
+                var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
+                var textBlock = window.FindControl<TextBlock>("textBlock");
+
+                var dataContext = new ImplicitConvertible("Green");
+                window.DataContext = dataContext;
+
+                var brush = Assert.IsType<SolidColorBrush>(textBlock.Background);
+                Assert.Equal(Colors.Green, brush.Color);
+            }
+        }
+
+        static void Throws(string type, Action cb)
+        {
+            try
+            {
+                cb();
+            }
+            catch (Exception e) when (e.GetType().Name == type)
+            {
+                return;
+            }
+
+            throw new Exception("Expected " + type);
+        }
         
         static void PerformClick(Button button)
         {
@@ -1921,6 +2022,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
     
     public class TestDataContext : TestDataContextBaseClass, IHasPropertyDerived, IHasExplicitProperty
     {
+        public bool BoolProperty { get; set; }
         public string? StringProperty { get; set; }
 
         public Task<string>? TaskProperty { get; set; }
@@ -2069,4 +2171,16 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
         [InheritDataTypeFromItems(nameof(DataGridLikeControl.Items), AncestorType = typeof(DataGridLikeControl))]
         public IDataTemplate? Template { get; set; }
     }
+
+    public class ImplicitConvertible
+    {
+        public ImplicitConvertible(string value) => Value = value;
+        
+        public string Value { get; }
+        
+        public static implicit operator Avalonia.Media.Color(ImplicitConvertible value)
+        {
+            return Color.Parse(value.Value);
+        }
+    }
 }
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/DynamicResourceExtensionTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/DynamicResourceExtensionTests.cs
index 523b31e60..9379f94ed 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/DynamicResourceExtensionTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/MarkupExtensions/DynamicResourceExtensionTests.cs
@@ -896,6 +896,34 @@ namespace Avalonia.Markup.Xaml.UnitTests.MarkupExtensions
             Assert.DoesNotContain("foo", resourceProvider.RequestedResources);
         }
 
+        [Fact]
+        public void Can_Detach_Control_With_DynamicResource_ControlTheme_That_Contains_DynamicResource()
+        {
+            using var app = UnitTestApplication.Start(TestServices.StyledWindow);
+            var xaml = $@"
+<Window xmlns='https://github.com/avaloniaui'
+    xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+    RequestedThemeVariant='Light'>
+    <Window.Resources>
+        <SolidColorBrush x:Key='Blue'>Blue</SolidColorBrush>
+        <ControlTheme x:Key='MyTheme' TargetType='Button'>
+            <Setter Property='Background' Value='{{DynamicResource Blue}}'/>
+        </ControlTheme>
+    </Window.Resources>
+
+    <Button Theme='{{DynamicResource MyTheme}}'/>
+</Window>";
+
+            var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
+            var target = Assert.IsType<Button>(window.Content);
+
+            window.Show();
+
+            Assert.Equal(Colors.Blue, ((ISolidColorBrush)target.Background).Color);
+
+            window.Content = null;
+        }
+
         private IDisposable StyledWindow(params (string, string)[] assets)
         {
             var services = TestServices.StyledWindow.With(
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/BindingTests_RelativeSource.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/BindingTests_RelativeSource.cs
index ee7b5d062..7b5d29881 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/BindingTests_RelativeSource.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/BindingTests_RelativeSource.cs
@@ -73,25 +73,6 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
             }
         }
 
-        [Fact]
-        public void Binding_To_First_Ancestor_Without_AncestorType_Throws_Exception()
-        {
-            using (UnitTestApplication.Start(TestServices.StyledWindow))
-            {
-                var xaml = @"
-<Window xmlns='https://github.com/avaloniaui'
-        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
-        xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.Xaml;assembly=Avalonia.Markup.Xaml.UnitTests'>
-    <Border Name='border1'>
-      <ContentControl Name='contentControl'>
-        <Button Name='button' Content='{Binding Name, RelativeSource={RelativeSource AncestorLevel=1}}'/>
-      </ContentControl>
-    </Border>
-</Window>";
-                Assert.Throws<InvalidOperationException>( () => AvaloniaRuntimeXamlLoader.Load(xaml));
-            }
-        }
-
         [Fact]
         public void Binding_To_First_Ancestor_With_Shorthand_Works()
         {
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlBindingTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlBindingTests.cs
index 6018e2438..b7a3f5dc7 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlBindingTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlBindingTests.cs
@@ -1,7 +1,6 @@
 using System.Collections.Generic;
 using Avalonia.Controls;
 using Avalonia.Controls.Primitives;
-using Avalonia.Logging;
 using Avalonia.UnitTests;
 using Xunit;
 
@@ -28,43 +27,6 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
             }
         }
 
-        [Fact]
-        public void Invalid_FallbackValue_Logs_Error()
-        {
-            var called = false;
-
-            LogCallback checkLogMessage = (level, area, src, mt, pv) =>
-            {
-                if (level == LogEventLevel.Warning &&
-                    area == LogArea.Binding &&
-                    mt == "Error in binding to {Target}.{Property}: {Message}" &&
-                    pv.Length == 3 &&
-                    pv[0] is ProgressBar &&
-                    object.ReferenceEquals(pv[1], ProgressBar.ValueProperty) &&
-                    (string)pv[2] == "Could not convert FallbackValue 'bar' to 'System.Double'")
-                {
-                    called = true;
-                }
-            };
-
-            using (UnitTestApplication.Start(TestServices.StyledWindow))
-            using (TestLogSink.Start(checkLogMessage))
-            {
-                var xaml = @"
-<Window xmlns='https://github.com/avaloniaui'>
-    <ProgressBar Maximum='10' Value='{Binding Value, FallbackValue=bar}'/>
-</Window>";
-                var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
-                var progressBar = (ProgressBar)window.Content;
-
-                window.DataContext = new { Value = "foo" };
-                window.ApplyTemplate();
-
-                Assert.Equal(0, progressBar.Value);
-                Assert.True(called);
-            }
-        }
-
         [Fact]
         public void Can_Bind_Between_TabStrip_And_Carousel()
         {
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlThemeTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlThemeTests.cs
index e153f1112..66ad6b6d6 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlThemeTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlThemeTests.cs
@@ -38,6 +38,36 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
             }
         }
 
+        [Fact]
+        public void ControlTheme_Can_Be_DynamicResource()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = $@"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:u='using:Avalonia.Markup.Xaml.UnitTests.Xaml'>
+    <Window.Resources>
+        {ControlThemeXaml}
+    </Window.Resources>
+
+    <u:TestTemplatedControl Theme='{{DynamicResource MyTheme}}'/>
+</Window>";
+
+                var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
+                var button = Assert.IsType<TestTemplatedControl>(window.Content);
+
+                window.Show();
+
+                Assert.NotNull(button.Template);
+
+                var child = Assert.Single(button.GetVisualChildren());
+                var border = Assert.IsType<Border>(child);
+
+                Assert.Equal(Brushes.Red, border.Background);
+            }
+        }
+
         [Fact]
         public void ControlTheme_Can_Be_Set_In_Style()
         {