diff --git a/nukebuild/_build.csproj b/nukebuild/_build.csproj
index d03746766e..8999b7ca76 100644
--- a/nukebuild/_build.csproj
+++ b/nukebuild/_build.csproj
@@ -15,7 +15,7 @@
     <PackageReference Include="vswhere" Version="2.6.7" Condition=" '$(OS)' == 'Windows_NT' " />
     <PackageReference Include="MicroCom.CodeGenerator" Version="0.11.0" />
     <!-- Keep in sync with Avalonia.Build.Tasks -->
-    <PackageReference Include="Mono.Cecil" Version="0.11.4" />
+    <PackageReference Include="Mono.Cecil" Version="0.11.5" />
     <PackageReference Include="SourceLink" Version="1.1.0" GeneratePathProperty="true" />
     <PackageReference Include="Microsoft.Build.Framework" Version="17.3.2" PrivateAssets="All" />
     <PackageReference Include="xunit.runner.console" Version="2.4.2">
diff --git a/samples/SafeAreaDemo.Desktop/SafeAreaDemo.Desktop.csproj b/samples/SafeAreaDemo.Desktop/SafeAreaDemo.Desktop.csproj
index 619209892d..a3b020d531 100644
--- a/samples/SafeAreaDemo.Desktop/SafeAreaDemo.Desktop.csproj
+++ b/samples/SafeAreaDemo.Desktop/SafeAreaDemo.Desktop.csproj
@@ -14,7 +14,7 @@
 
   <ItemGroup>
     <ProjectReference Include="..\..\src\Avalonia.Diagnostics\Avalonia.Diagnostics.csproj" />
-    <ProjectReference Include="..\..\src\Avalonia.Headless.Vnc\Avalonia.Headless.Vnc.csproj" />
+    <ProjectReference Include="..\..\src\Headless\Avalonia.Headless.Vnc\Avalonia.Headless.Vnc.csproj" />
     <ProjectReference Include="..\..\src\Linux\Avalonia.LinuxFramebuffer\Avalonia.LinuxFramebuffer.csproj" />
     <ProjectReference Include="..\..\src\Avalonia.X11\Avalonia.X11.csproj" />
     <ProjectReference Include="..\SafeAreaDemo\SafeAreaDemo.csproj" />
diff --git a/src/Avalonia.Base/AttachedProperty.cs b/src/Avalonia.Base/AttachedProperty.cs
index 4a09f2a80a..6269df2a26 100644
--- a/src/Avalonia.Base/AttachedProperty.cs
+++ b/src/Avalonia.Base/AttachedProperty.cs
@@ -13,16 +13,18 @@ namespace Avalonia
         /// </summary>
         /// <param name="name">The name of the property.</param>
         /// <param name="ownerType">The class that is registering the property.</param>
+        /// <param name="hostType">The class that the property being is registered on.</param>
         /// <param name="metadata">The property metadata.</param>
         /// <param name="inherits">Whether the property inherits its value.</param>
         /// <param name="validate">A value validation callback.</param>
-        public AttachedProperty(
+        internal AttachedProperty(
             string name,
             Type ownerType,
+            Type hostType,
             StyledPropertyMetadata<TValue> metadata,
             bool inherits = false,
             Func<TValue, bool>? validate = null)
-            : base(name, ownerType, metadata, inherits, validate)
+            : base(name, ownerType, hostType, metadata, inherits, validate)
         {
             IsAttached = true;
         }
diff --git a/src/Avalonia.Base/AvaloniaProperty.cs b/src/Avalonia.Base/AvaloniaProperty.cs
index c57131f7b5..95f8eea852 100644
--- a/src/Avalonia.Base/AvaloniaProperty.cs
+++ b/src/Avalonia.Base/AvaloniaProperty.cs
@@ -39,12 +39,14 @@ namespace Avalonia
         /// <param name="name">The name of the property.</param>
         /// <param name="valueType">The type of the property's value.</param>
         /// <param name="ownerType">The type of the class that registers the property.</param>
+        /// <param name="hostType">The class that the property being is registered on.</param>
         /// <param name="metadata">The property metadata.</param>
         /// <param name="notifying">A <see cref="Notifying"/> callback.</param>
-        protected AvaloniaProperty(
+        private protected AvaloniaProperty(
             string name,
             Type valueType,
             Type ownerType,
+            Type hostType,
             AvaloniaPropertyMetadata metadata,
             Action<AvaloniaObject, bool>? notifying = null)
         {
@@ -63,9 +65,9 @@ namespace Avalonia
             Notifying = notifying;
             Id = s_nextId++;
 
-            _metadata.Add(ownerType, metadata ?? throw new ArgumentNullException(nameof(metadata)));
+            _metadata.Add(hostType, metadata ?? throw new ArgumentNullException(nameof(metadata)));
             _defaultMetadata = metadata.GenerateTypeSafeMetadata();
-            _singleMetadata = new(ownerType, metadata);
+            _singleMetadata = new(hostType, metadata);
         }
 
         /// <summary>
@@ -74,7 +76,7 @@ namespace Avalonia
         /// <param name="source">The direct property to copy.</param>
         /// <param name="ownerType">The new owner type.</param>
         /// <param name="metadata">Optional overridden metadata.</param>
-        protected AvaloniaProperty(
+        private protected AvaloniaProperty(
             AvaloniaProperty source,
             Type ownerType,
             AvaloniaPropertyMetadata? metadata)
@@ -151,7 +153,7 @@ namespace Avalonia
         /// will be true before the property change notifications are sent and false afterwards. This
         /// callback is intended to support Control.IsDataContextChanging.
         /// </remarks>
-        public Action<AvaloniaObject, bool>? Notifying { get; }
+        internal Action<AvaloniaObject, bool>? Notifying { get; }
 
         /// <summary>
         /// Gets the integer ID that represents this property.
@@ -255,6 +257,7 @@ namespace Avalonia
             var result = new StyledProperty<TValue>(
                 name,
                 typeof(TOwner),
+                typeof(TOwner),
                 metadata,
                 inherits,
                 validate);
@@ -301,6 +304,7 @@ namespace Avalonia
             var result = new StyledProperty<TValue>(
                 name,
                 typeof(TOwner),
+                typeof(TOwner),
                 metadata,
                 inherits,
                 validate,
@@ -338,7 +342,7 @@ namespace Avalonia
                 defaultBindingMode: defaultBindingMode,
                 coerce: coerce);
 
-            var result = new AttachedProperty<TValue>(name, typeof(TOwner), metadata, inherits, validate);
+            var result = new AttachedProperty<TValue>(name, typeof(TOwner), typeof(THost), metadata, inherits, validate);
             var registry = AvaloniaPropertyRegistry.Instance;
             registry.Register(typeof(TOwner), result);
             registry.RegisterAttached(typeof(THost), result);
@@ -375,7 +379,7 @@ namespace Avalonia
                 defaultBindingMode: defaultBindingMode,
                 coerce: coerce);
 
-            var result = new AttachedProperty<TValue>(name, ownerType, metadata, inherits, validate);
+            var result = new AttachedProperty<TValue>(name, ownerType, typeof(THost), metadata, inherits, validate);
             var registry = AvaloniaPropertyRegistry.Instance;
             registry.Register(ownerType, result);
             registry.RegisterAttached(typeof(THost), result);
@@ -554,7 +558,7 @@ namespace Avalonia
         /// </summary>
         /// <param name="type">The type.</param>
         /// <param name="metadata">The metadata.</param>
-        protected void OverrideMetadata(Type type, AvaloniaPropertyMetadata metadata)
+        private protected void OverrideMetadata(Type type, AvaloniaPropertyMetadata metadata)
         {
             _ = type ?? throw new ArgumentNullException(nameof(type));
             _ = metadata ?? throw new ArgumentNullException(nameof(metadata));
@@ -573,7 +577,7 @@ namespace Avalonia
             _singleMetadata = null;
         }
 
-        protected abstract IObservable<AvaloniaPropertyChangedEventArgs> GetChanged();
+        private protected abstract IObservable<AvaloniaPropertyChangedEventArgs> GetChanged();
 
         private AvaloniaPropertyMetadata GetMetadataWithOverrides(Type type)
         {
diff --git a/src/Avalonia.Base/AvaloniaProperty`1.cs b/src/Avalonia.Base/AvaloniaProperty`1.cs
index f8c062a176..ea2f3577e5 100644
--- a/src/Avalonia.Base/AvaloniaProperty`1.cs
+++ b/src/Avalonia.Base/AvaloniaProperty`1.cs
@@ -19,14 +19,16 @@ namespace Avalonia
         /// </summary>
         /// <param name="name">The name of the property.</param>
         /// <param name="ownerType">The type of the class that registers the property.</param>
+        /// <param name="hostType">The class that the property being is registered on.</param>
         /// <param name="metadata">The property metadata.</param>
         /// <param name="notifying">A <see cref="AvaloniaProperty.Notifying"/> callback.</param>
-        protected AvaloniaProperty(
+        private protected AvaloniaProperty(
             string name,
             Type ownerType,
+            Type hostType,
             AvaloniaPropertyMetadata metadata,
             Action<AvaloniaObject, bool>? notifying = null)
-            : base(name, typeof(TValue), ownerType, metadata, notifying)
+            : base(name, typeof(TValue), ownerType, hostType, metadata, notifying)
         {
             _changed = new LightweightSubject<AvaloniaPropertyChangedEventArgs<TValue>>();
         }
@@ -37,7 +39,7 @@ namespace Avalonia
         /// <param name="source">The property to copy.</param>
         /// <param name="ownerType">The new owner type.</param>
         /// <param name="metadata">Optional overridden metadata.</param>
-        protected AvaloniaProperty(
+        private protected AvaloniaProperty(
             AvaloniaProperty<TValue> source,
             Type ownerType,
             AvaloniaPropertyMetadata? metadata)
@@ -66,10 +68,10 @@ namespace Avalonia
             _changed.OnNext(e);
         }
 
-        protected override IObservable<AvaloniaPropertyChangedEventArgs> GetChanged() => Changed;
+        private protected override IObservable<AvaloniaPropertyChangedEventArgs> GetChanged() => Changed;
 
         [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = TrimmingMessages.ImplicitTypeConvertionSupressWarningMessage)]
-        protected BindingValue<object?> TryConvert(object? value)
+        private protected BindingValue<object?> TryConvert(object? value)
         {
             if (value == UnsetValue)
             {
diff --git a/src/Avalonia.Base/DirectProperty.cs b/src/Avalonia.Base/DirectProperty.cs
index d02e277074..dd02553eaf 100644
--- a/src/Avalonia.Base/DirectProperty.cs
+++ b/src/Avalonia.Base/DirectProperty.cs
@@ -24,7 +24,7 @@ namespace Avalonia
         /// <param name="getter">Gets the current value of the property.</param>
         /// <param name="setter">Sets the value of the property. May be null.</param>
         /// <param name="metadata">The property metadata.</param>
-        public DirectProperty(
+        internal DirectProperty(
             string name,
             Func<TOwner, TValue> getter,
             Action<TOwner, TValue>? setter,
@@ -106,45 +106,6 @@ namespace Avalonia
             return result;
         }
 
-        /// <summary>
-        /// Registers the direct property on another type.
-        /// </summary>
-        /// <typeparam name="TNewOwner">The type of the additional owner.</typeparam>
-        /// <param name="getter">Gets the current value of the property.</param>
-        /// <param name="setter">Sets the value of the property.</param>
-        /// <param name="unsetValue">
-        /// The value to use when the property is set to <see cref="AvaloniaProperty.UnsetValue"/>
-        /// </param>
-        /// <param name="defaultBindingMode">The default binding mode for the property.</param>
-        /// <param name="enableDataValidation">
-        /// Whether the property is interested in data validation.
-        /// </param>
-        /// <returns>The property.</returns>
-        public DirectProperty<TNewOwner, TValue> AddOwnerWithDataValidation<TNewOwner>(
-            Func<TNewOwner, TValue> getter,
-            Action<TNewOwner,TValue> setter,
-            TValue unsetValue = default!,
-            BindingMode defaultBindingMode = BindingMode.Default,
-            bool enableDataValidation = false)
-                where TNewOwner : AvaloniaObject
-        {
-            var metadata = new DirectPropertyMetadata<TValue>(
-                unsetValue: unsetValue,
-                defaultBindingMode: defaultBindingMode,
-                enableDataValidation: enableDataValidation);
-
-            metadata.Merge(GetMetadata<TOwner>(), this);
-
-            var result = new DirectProperty<TNewOwner, TValue>(
-                this,
-                getter,
-                setter,
-                metadata);
-
-            AvaloniaPropertyRegistry.Instance.Register(typeof(TNewOwner), result);
-            return result;
-        }
-
         /// <inheritdoc/>
         internal override TValue InvokeGetter(AvaloniaObject instance)
         {
diff --git a/src/Avalonia.Base/DirectPropertyBase.cs b/src/Avalonia.Base/DirectPropertyBase.cs
index 7e5a962157..4dddc12794 100644
--- a/src/Avalonia.Base/DirectPropertyBase.cs
+++ b/src/Avalonia.Base/DirectPropertyBase.cs
@@ -20,11 +20,11 @@ namespace Avalonia
         /// <param name="name">The name of the property.</param>
         /// <param name="ownerType">The type of the class that registers the property.</param>
         /// <param name="metadata">The property metadata.</param>
-        protected DirectPropertyBase(
+        private protected DirectPropertyBase(
             string name,
             Type ownerType,
             AvaloniaPropertyMetadata metadata)
-            : base(name, ownerType, metadata)
+            : base(name, ownerType, ownerType, metadata)
         {
             Owner = ownerType;
         }
@@ -35,7 +35,7 @@ namespace Avalonia
         /// <param name="source">The property to copy.</param>
         /// <param name="ownerType">The new owner type.</param>
         /// <param name="metadata">Optional overridden metadata.</param>
-        protected DirectPropertyBase(
+        private protected DirectPropertyBase(
             DirectPropertyBase<TValue> source,
             Type ownerType,
             AvaloniaPropertyMetadata metadata)
diff --git a/src/Avalonia.Base/StyledElement.cs b/src/Avalonia.Base/StyledElement.cs
index 3270fe4614..196fa850d6 100644
--- a/src/Avalonia.Base/StyledElement.cs
+++ b/src/Avalonia.Base/StyledElement.cs
@@ -30,10 +30,12 @@ namespace Avalonia
         ILogical,
         IThemeVariantHost,
         IStyleHost,
-        IStyleable,
         ISetLogicalParent,
         ISetInheritanceParent,
-        ISupportInitialize
+        ISupportInitialize,
+#pragma warning disable CS0618 // Type or member is obsolete
+        IStyleable
+#pragma warning restore CS0618 // Type or member is obsolete
     {
         /// <summary>
         /// Defines the <see cref="DataContext"/> property.
@@ -217,6 +219,18 @@ namespace Avalonia
         /// </remarks>
         public Styles Styles => _styles ??= new Styles(this);
 
+        /// <summary>
+        /// Gets the type by which the element is styled.
+        /// </summary>
+        /// <remarks>
+        /// Usually controls are styled by their own type, but there are instances where you want
+        /// an element to be styled by its base type, e.g. creating SpecialButton that
+        /// derives from Button and adds extra functionality but is still styled as a regular
+        /// Button. To change the style for a control class, override the <see cref="StyleKeyOverride"/>
+        /// property
+        /// </remarks>
+        public Type StyleKey => StyleKeyOverride;
+
         /// <summary>
         /// Gets or sets the styled element's resource dictionary.
         /// </summary>
@@ -278,6 +292,18 @@ namespace Avalonia
         /// </summary>
         protected IPseudoClasses PseudoClasses => Classes;
 
+        /// <summary>
+        /// Gets the type by which the element is styled.
+        /// </summary>
+        /// <remarks>
+        /// Usually controls are styled by their own type, but there are instances where you want
+        /// an element to be styled by its base type, e.g. creating SpecialButton that
+        /// derives from Button and adds extra functionality but is still styled as a regular
+        /// Button. Override this property to change the style for a control class, returning the
+        /// type that you wish the elements to be styled as.
+        /// </remarks>
+        protected virtual Type StyleKeyOverride => GetType();
+
         /// <summary>
         /// Gets a value indicating whether the element is attached to a rooted logical tree.
         /// </summary>
@@ -309,24 +335,12 @@ namespace Avalonia
         /// <inheritdoc/>
         IAvaloniaReadOnlyList<string> IStyleable.Classes => Classes;
 
-        /// <summary>
-        /// Gets the type by which the styled element is styled.
-        /// </summary>
-        /// <remarks>
-        /// Usually controls are styled by their own type, but there are instances where you want
-        /// a styled element to be styled by its base type, e.g. creating SpecialButton that
-        /// derives from Button and adds extra functionality but is still styled as a regular
-        /// Button.
-        /// </remarks>
-        Type IStyleable.StyleKey => GetType();
-
         /// <inheritdoc/>
         bool IStyleHost.IsStylesInitialized => _styles != null;
 
         /// <inheritdoc/>
         IStyleHost? IStyleHost.StylingParent => (IStyleHost?)InheritanceParent;
 
-
         /// <inheritdoc/>
         public virtual void BeginInit()
         {
@@ -669,7 +683,7 @@ namespace Avalonia
             // If the Theme property is not set, try to find a ControlTheme resource with our StyleKey.
             if (_implicitTheme is null)
             {
-                var key = ((IStyleable)this).StyleKey;
+                var key = GetStyleKey(this);
 
                 if (this.TryFindResource(key, out var value) && value is ControlTheme t)
                     _implicitTheme = t;
@@ -700,6 +714,22 @@ namespace Avalonia
             }
         }
 
+        /// <summary>
+        /// Internal getter for <see cref="IStyleable.StyleKey"/> so that we only need to suppress the obsolete
+        /// warning in one place.
+        /// </summary>
+        /// <param name="e">The element</param>
+        /// <remarks>
+        /// <see cref="IStyleable"/> is obsolete and will be removed in a future version, but for backwards
+        /// compatibility we need to support code which overrides <see cref="IStyleable.StyleKey"/>.
+        /// </remarks>
+        internal static Type GetStyleKey(StyledElement e)
+        {
+#pragma warning disable CS0618 // Type or member is obsolete
+            return ((IStyleable)e).StyleKey;
+#pragma warning restore CS0618 // Type or member is obsolete
+        }
+
         private static void DataContextNotifying(AvaloniaObject o, bool updateStarted)
         {
             if (o is StyledElement element)
diff --git a/src/Avalonia.Base/StyledProperty.cs b/src/Avalonia.Base/StyledProperty.cs
index 5cb330eda9..ee8748956e 100644
--- a/src/Avalonia.Base/StyledProperty.cs
+++ b/src/Avalonia.Base/StyledProperty.cs
@@ -16,6 +16,7 @@ namespace Avalonia
         /// </summary>
         /// <param name="name">The name of the property.</param>
         /// <param name="ownerType">The type of the class that registers the property.</param>
+        /// <param name="hostType">The class that the property being is registered on.</param>
         /// <param name="metadata">The property metadata.</param>
         /// <param name="inherits">Whether the property inherits its value.</param>
         /// <param name="validate">
@@ -23,14 +24,15 @@ namespace Avalonia
         /// <para>This method is not part of the property's metadata and so cannot be changed after registration.</para>
         /// </param>
         /// <param name="notifying">A <see cref="AvaloniaProperty.Notifying"/> callback.</param>
-        public StyledProperty(
+        internal StyledProperty(
             string name,
             Type ownerType,
+            Type hostType,
             StyledPropertyMetadata<TValue> metadata,
             bool inherits = false,
             Func<TValue, bool>? validate = null,
             Action<AvaloniaObject, bool>? notifying = null)
-                : base(name, ownerType, metadata, notifying)
+                : base(name, ownerType, hostType, metadata, notifying)
         {
             Inherits = inherits;
             ValidateValue = validate;
diff --git a/src/Avalonia.Base/Styling/ControlTheme.cs b/src/Avalonia.Base/Styling/ControlTheme.cs
index 22c8f61577..75a3beb907 100644
--- a/src/Avalonia.Base/Styling/ControlTheme.cs
+++ b/src/Avalonia.Base/Styling/ControlTheme.cs
@@ -46,7 +46,7 @@ namespace Avalonia.Styling
             if (TargetType is null)
                 throw new InvalidOperationException("ControlTheme has no TargetType.");
 
-            if (HasSettersOrAnimations && TargetType.IsAssignableFrom(((IStyleable)target).StyleKey))
+            if (HasSettersOrAnimations && TargetType.IsAssignableFrom(StyledElement.GetStyleKey(target)))
             {
                 Attach(target, null, type);
                 return SelectorMatchResult.AlwaysThisType;
diff --git a/src/Avalonia.Base/Styling/DescendentSelector.cs b/src/Avalonia.Base/Styling/DescendentSelector.cs
index 77ae0f2877..20874a6877 100644
--- a/src/Avalonia.Base/Styling/DescendentSelector.cs
+++ b/src/Avalonia.Base/Styling/DescendentSelector.cs
@@ -44,9 +44,9 @@ namespace Avalonia.Styling
             {
                 c = c.LogicalParent;
 
-                if (c is IStyleable)
+                if (c is StyledElement s)
                 {
-                    var match = _parent.Match((StyledElement)c, parent, subscribe);
+                    var match = _parent.Match(s, parent, subscribe);
 
                     if (match.Result == SelectorMatchResult.Sometimes)
                     {
diff --git a/src/Avalonia.Base/Styling/IStyleable.cs b/src/Avalonia.Base/Styling/IStyleable.cs
index a6cc2c0f76..0768669905 100644
--- a/src/Avalonia.Base/Styling/IStyleable.cs
+++ b/src/Avalonia.Base/Styling/IStyleable.cs
@@ -1,13 +1,12 @@
 using System;
 using Avalonia.Collections;
-using Avalonia.Metadata;
 
 namespace Avalonia.Styling
 {
     /// <summary>
     /// Interface for styleable elements.
     /// </summary>
-    [NotClientImplementable]
+    [Obsolete("This interface may be removed in 12.0. Use StyledElement, or override StyledElement.StyleKeyOverride to override the StyleKey for a class.")]
     public interface IStyleable : INamed
     {
         /// <summary>
@@ -18,6 +17,7 @@ namespace Avalonia.Styling
         /// <summary>
         /// Gets the type by which the control is styled.
         /// </summary>
+        [Obsolete("Override StyledElement.StyleKeyOverride instead.")]
         Type StyleKey { get; }
 
         /// <summary>
diff --git a/src/Avalonia.Base/Styling/NestingSelector.cs b/src/Avalonia.Base/Styling/NestingSelector.cs
index 980bf12907..deb688ca4d 100644
--- a/src/Avalonia.Base/Styling/NestingSelector.cs
+++ b/src/Avalonia.Base/Styling/NestingSelector.cs
@@ -23,7 +23,7 @@ namespace Avalonia.Styling
             {
                 if (theme.TargetType is null)
                     throw new InvalidOperationException("ControlTheme has no TargetType.");
-                return theme.TargetType.IsAssignableFrom(((IStyleable)control).StyleKey) ?
+                return theme.TargetType.IsAssignableFrom(StyledElement.GetStyleKey(control)) ?
                     SelectorMatch.AlwaysThisType :
                     SelectorMatch.NeverThisType;
             }
diff --git a/src/Avalonia.Base/Styling/Selectors.cs b/src/Avalonia.Base/Styling/Selectors.cs
index 476d86cd11..d7406f2164 100644
--- a/src/Avalonia.Base/Styling/Selectors.cs
+++ b/src/Avalonia.Base/Styling/Selectors.cs
@@ -76,7 +76,7 @@ namespace Avalonia.Styling
         /// <typeparam name="T">The type.</typeparam>
         /// <param name="previous">The previous selector.</param>
         /// <returns>The selector.</returns>
-        public static Selector Is<T>(this Selector? previous) where T : IStyleable
+        public static Selector Is<T>(this Selector? previous) where T : StyledElement
         {
             return previous.Is(typeof(T));
         }
@@ -171,7 +171,7 @@ namespace Avalonia.Styling
         /// <typeparam name="T">The type.</typeparam>
         /// <param name="previous">The previous selector.</param>
         /// <returns>The selector.</returns>
-        public static Selector OfType<T>(this Selector? previous) where T : IStyleable
+        public static Selector OfType<T>(this Selector? previous) where T : StyledElement
         {
             return previous.OfType(typeof(T));
         }
diff --git a/src/Avalonia.Base/Styling/TypeNameAndClassSelector.cs b/src/Avalonia.Base/Styling/TypeNameAndClassSelector.cs
index a10b3eb3ea..2bd05242f5 100644
--- a/src/Avalonia.Base/Styling/TypeNameAndClassSelector.cs
+++ b/src/Avalonia.Base/Styling/TypeNameAndClassSelector.cs
@@ -93,7 +93,7 @@ namespace Avalonia.Styling
         {
             if (TargetType != null)
             {
-                var controlType = ((IStyleable)control).StyleKey ?? control.GetType();
+                var controlType = StyledElement.GetStyleKey(control) ?? control.GetType();
 
                 if (IsConcreteType)
                 {
diff --git a/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj b/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj
index b654c66157..4f9c7416db 100644
--- a/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj
+++ b/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj
@@ -118,7 +118,7 @@
       <Compile Include="..\Avalonia.Base\Utilities\SpanHelpers.cs" Link="Utilities\SpanHelpers.cs" />
       <Compile Remove="../Markup/Avalonia.Markup.Xaml.Loader\xamlil.github\**\obj\**\*.cs" />
       <Compile Remove="../Markup/Avalonia.Markup.Xaml.Loader\xamlil.github\src\XamlX\IL\SreTypeSystem.cs" />
-      <PackageReference Include="Mono.Cecil" Version="0.11.4" />
+      <PackageReference Include="Mono.Cecil" Version="0.11.5" />
       <PackageReference Include="Microsoft.Build.Framework" Version="15.1.548" PrivateAssets="All" />
       <PackageReference Include="System.Numerics.Vectors" Version="4.5.0" />
     </ItemGroup>
diff --git a/src/Avalonia.Controls/Embedding/EmbeddableControlRoot.cs b/src/Avalonia.Controls/Embedding/EmbeddableControlRoot.cs
index b79fef55b9..7a0ab36050 100644
--- a/src/Avalonia.Controls/Embedding/EmbeddableControlRoot.cs
+++ b/src/Avalonia.Controls/Embedding/EmbeddableControlRoot.cs
@@ -7,7 +7,7 @@ using Avalonia.Styling;
 
 namespace Avalonia.Controls.Embedding
 {
-    public class EmbeddableControlRoot : TopLevel, IStyleable, IFocusScope, IDisposable
+    public class EmbeddableControlRoot : TopLevel, IFocusScope, IDisposable
     {
         public EmbeddableControlRoot(ITopLevelImpl impl) : base(impl)
         {
@@ -46,7 +46,7 @@ namespace Avalonia.Controls.Embedding
             return rv;
         }
 
-        Type IStyleable.StyleKey => typeof(EmbeddableControlRoot);
+        protected override Type StyleKeyOverride => typeof(EmbeddableControlRoot);
         public void Dispose() => PlatformImpl?.Dispose();
     }
 }
diff --git a/src/Avalonia.Controls/Embedding/Offscreen/OffscreenTopLevel.cs b/src/Avalonia.Controls/Embedding/Offscreen/OffscreenTopLevel.cs
index b037dd9901..a87e36d00d 100644
--- a/src/Avalonia.Controls/Embedding/Offscreen/OffscreenTopLevel.cs
+++ b/src/Avalonia.Controls/Embedding/Offscreen/OffscreenTopLevel.cs
@@ -4,7 +4,7 @@ using Avalonia.Styling;
 
 namespace Avalonia.Controls.Embedding.Offscreen
 {
-    class OffscreenTopLevel : TopLevel, IStyleable
+    class OffscreenTopLevel : TopLevel
     {
         public OffscreenTopLevelImplBase Impl { get; }
 
@@ -31,7 +31,7 @@ namespace Avalonia.Controls.Embedding.Offscreen
             }
         }
 
-        Type IStyleable.StyleKey => typeof(EmbeddableControlRoot);
+        protected override Type StyleKeyOverride => typeof(EmbeddableControlRoot);
         public void Dispose()
         {
             PlatformImpl?.Dispose();
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 064716fa9b..1613bda45b 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -712,7 +712,7 @@ namespace Avalonia.Controls
 
             if (itemContainerTheme is not null &&
                 !container.IsSet(ThemeProperty) &&
-                ((IStyleable)container).StyleKey == itemContainerTheme.TargetType)
+                StyledElement.GetStyleKey(container) == itemContainerTheme.TargetType)
             {
                 container.Theme = itemContainerTheme;
             }
diff --git a/src/Avalonia.Controls/MaskedTextBox.cs b/src/Avalonia.Controls/MaskedTextBox.cs
index f54e8b19db..4800b7b1e4 100644
--- a/src/Avalonia.Controls/MaskedTextBox.cs
+++ b/src/Avalonia.Controls/MaskedTextBox.cs
@@ -10,7 +10,7 @@ using Avalonia.Styling;
 
 namespace Avalonia.Controls
 {
-    public class MaskedTextBox : TextBox, IStyleable
+    public class MaskedTextBox : TextBox
     {
         public static readonly StyledProperty<bool> AsciiOnlyProperty =
              AvaloniaProperty.Register<MaskedTextBox, bool>(nameof(AsciiOnly));
@@ -183,7 +183,7 @@ namespace Avalonia.Controls
             set => SetValue(ResetOnSpaceProperty, value);
         }
 
-        Type IStyleable.StyleKey => typeof(TextBox);
+        protected override Type StyleKeyOverride => typeof(TextBox);
 
         /// <inheritdoc />
         protected override void OnGotFocus(GotFocusEventArgs e)
diff --git a/src/Avalonia.Controls/Selection/InternalSelectionModel.cs b/src/Avalonia.Controls/Selection/InternalSelectionModel.cs
index c8ad9bd88b..455700af1f 100644
--- a/src/Avalonia.Controls/Selection/InternalSelectionModel.cs
+++ b/src/Avalonia.Controls/Selection/InternalSelectionModel.cs
@@ -67,6 +67,8 @@ namespace Avalonia.Controls.Selection
             var previousSource = Source;
             var previousWritableSelectedItems = _writableSelectedItems;
 
+            base.OnSourceCollectionChangeStarted();
+            
             try
             {
                 _skipSyncFromSelectedItems = true;
@@ -81,8 +83,20 @@ namespace Avalonia.Controls.Selection
 
             // We skipped the sync from WritableSelectedItems before; do it now that both
             // the source and WritableSelectedItems are updated.
-            if (previousSource != Source || previousWritableSelectedItems != _writableSelectedItems)
+            if (previousWritableSelectedItems != _writableSelectedItems)
+            {
+                base.OnSourceCollectionChangeFinished();
+                SyncFromSelectedItems();
+            }
+            else if (previousSource != Source)
+            {
                 SyncFromSelectedItems();
+                base.OnSourceCollectionChangeFinished();
+            }
+            else
+            {
+                base.OnSourceCollectionChangeFinished();
+            }
         }
 
         private protected override void SetSource(IEnumerable? value)
diff --git a/src/Avalonia.Controls/SplitButton/ToggleSplitButton.cs b/src/Avalonia.Controls/SplitButton/ToggleSplitButton.cs
index 509b58833f..ff8bd5dc0b 100644
--- a/src/Avalonia.Controls/SplitButton/ToggleSplitButton.cs
+++ b/src/Avalonia.Controls/SplitButton/ToggleSplitButton.cs
@@ -13,7 +13,7 @@ namespace Avalonia.Controls
     /// the secondary part opens a flyout.
     /// </summary>
     [PseudoClasses(pcChecked)]
-    public class ToggleSplitButton : SplitButton, IStyleable
+    public class ToggleSplitButton : SplitButton
     {
         /// <summary>
         /// Raised when the <see cref="IsChecked"/> property value changes.
@@ -63,7 +63,7 @@ namespace Avalonia.Controls
         /// Both <see cref="ToggleSplitButton"/> and <see cref="SplitButton"/> share
         /// the same exact default style.
         /// </remarks>
-        Type IStyleable.StyleKey => typeof(SplitButton);
+        protected override Type StyleKeyOverride => typeof(SplitButton);
 
         /// <summary>
         /// Toggles the <see cref="IsChecked"/> property between true and false.
diff --git a/src/Avalonia.Controls/UserControl.cs b/src/Avalonia.Controls/UserControl.cs
index e9339d5f4b..40c312be42 100644
--- a/src/Avalonia.Controls/UserControl.cs
+++ b/src/Avalonia.Controls/UserControl.cs
@@ -5,7 +5,7 @@ namespace Avalonia.Controls
     /// <summary>
     /// Provides the base class for defining a new control that encapsulates related existing controls and provides its own logic.
     /// </summary>
-    public class UserControl : ContentControl, IStyleable
+    public class UserControl : ContentControl
     {
 
     }
diff --git a/src/Avalonia.Controls/Window.cs b/src/Avalonia.Controls/Window.cs
index 66cce89b9d..3f04350995 100644
--- a/src/Avalonia.Controls/Window.cs
+++ b/src/Avalonia.Controls/Window.cs
@@ -65,7 +65,7 @@ namespace Avalonia.Controls
     /// <summary>
     /// A top-level window.
     /// </summary>
-    public class Window : WindowBase, IStyleable, IFocusScope, ILayoutRoot
+    public class Window : WindowBase, IFocusScope, ILayoutRoot
     {
         private readonly List<(Window child, bool isDialog)> _children = new List<(Window, bool)>();
         private bool _isExtendedIntoWindowDecorations;
@@ -420,7 +420,7 @@ namespace Avalonia.Controls
         public void BeginResizeDrag(WindowEdge edge, PointerPressedEventArgs e) => PlatformImpl?.BeginResizeDrag(edge, e);
 
         /// <inheritdoc/>
-        Type IStyleable.StyleKey => typeof(Window);
+        protected override Type StyleKeyOverride => typeof(Window);
 
         /// <summary>
         /// Fired before a window is closed.
diff --git a/src/Avalonia.Diagnostics/Diagnostics/Controls/CommitTextBox.cs b/src/Avalonia.Diagnostics/Diagnostics/Controls/CommitTextBox.cs
index 7870febd0a..d724318641 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/Controls/CommitTextBox.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/Controls/CommitTextBox.cs
@@ -7,9 +7,9 @@ using Avalonia.Styling;
 namespace Avalonia.Diagnostics.Controls
 {
     //TODO: UpdateSourceTrigger & Binding.ValidationRules could help removing the need for this control.
-    internal sealed class CommitTextBox : TextBox, IStyleable
+    internal sealed class CommitTextBox : TextBox
     {
-        Type IStyleable.StyleKey => typeof(TextBox);
+        protected override Type StyleKeyOverride => typeof(TextBox);
 
         /// <summary>
         ///     Defines the <see cref="CommittedText" /> property.
diff --git a/src/Avalonia.Diagnostics/Diagnostics/Controls/FilterTextBox.cs b/src/Avalonia.Diagnostics/Diagnostics/Controls/FilterTextBox.cs
index 1e5674cc21..c703c73549 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/Controls/FilterTextBox.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/Controls/FilterTextBox.cs
@@ -5,7 +5,7 @@ using Avalonia.Styling;
 
 namespace Avalonia.Diagnostics.Controls
 {
-    internal class FilterTextBox : TextBox, IStyleable
+    internal class FilterTextBox : TextBox
     {
         public static readonly StyledProperty<bool> UseRegexFilterProperty =
             AvaloniaProperty.Register<FilterTextBox, bool>(nameof(UseRegexFilter),
@@ -42,6 +42,6 @@ namespace Avalonia.Diagnostics.Controls
             set => SetValue(UseWholeWordFilterProperty, value);
         }
 
-        Type IStyleable.StyleKey => typeof(TextBox);
+        protected override Type StyleKeyOverride => typeof(TextBox);
     }
 }
diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreePageViewModel.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreePageViewModel.cs
index 4e8b4c66a2..67dbfed92b 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreePageViewModel.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreePageViewModel.cs
@@ -208,7 +208,7 @@ namespace Avalonia.Diagnostics.ViewModels
             var classes = string.Concat(visual.Classes
                 .Where(c => !c.StartsWith(":"))
                 .Select(c => '.' + c));
-            var typeName = ((IStyleable)visual).StyleKey.Name;
+            var typeName = StyledElement.GetStyleKey(visual);
 
             return $"{typeName}{name}{classes}";
         } 
diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/VisualTreeNode.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/VisualTreeNode.cs
index c3ebb1beaf..8dbcd606b0 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/VisualTreeNode.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/VisualTreeNode.cs
@@ -23,7 +23,7 @@ namespace Avalonia.Diagnostics.ViewModels
                 _ => TreeNodeCollection.Empty
             };
 
-            if (Visual is IStyleable styleable)
+            if (Visual is StyledElement styleable)
                 IsInTemplate = styleable.TemplatedParent != null;
         }
 
diff --git a/src/Avalonia.ReactiveUI/RoutedViewHost.cs b/src/Avalonia.ReactiveUI/RoutedViewHost.cs
index 2d848d4cd7..701b0d0f46 100644
--- a/src/Avalonia.ReactiveUI/RoutedViewHost.cs
+++ b/src/Avalonia.ReactiveUI/RoutedViewHost.cs
@@ -50,7 +50,7 @@ namespace Avalonia.ReactiveUI
     /// ReactiveUI routing documentation website</see> for more info.
     /// </para>
     /// </remarks>
-    public class RoutedViewHost : TransitioningContentControl, IActivatableView, IEnableLogger, IStyleable
+    public class RoutedViewHost : TransitioningContentControl, IActivatableView, IEnableLogger
     {
         /// <summary>
         /// <see cref="AvaloniaProperty"/> for the <see cref="Router"/> property.
@@ -126,7 +126,7 @@ namespace Avalonia.ReactiveUI
         /// </summary>
         public IViewLocator? ViewLocator { get; set; }
 
-        Type IStyleable.StyleKey => typeof(TransitioningContentControl);
+        protected override Type StyleKeyOverride => typeof(TransitioningContentControl);
         
         /// <summary>
         /// Invoked when ReactiveUI router navigates to a view model.
diff --git a/src/Avalonia.ReactiveUI/ViewModelViewHost.cs b/src/Avalonia.ReactiveUI/ViewModelViewHost.cs
index dc45758046..3e7ed42662 100644
--- a/src/Avalonia.ReactiveUI/ViewModelViewHost.cs
+++ b/src/Avalonia.ReactiveUI/ViewModelViewHost.cs
@@ -13,7 +13,7 @@ namespace Avalonia.ReactiveUI
     /// the ViewModel property and display it. This control is very useful
     /// inside a DataTemplate to display the View associated with a ViewModel.
     /// </summary>
-    public class ViewModelViewHost : TransitioningContentControl, IViewFor, IEnableLogger, IStyleable
+    public class ViewModelViewHost : TransitioningContentControl, IViewFor, IEnableLogger
     {
         /// <summary>
         /// <see cref="AvaloniaProperty"/> for the <see cref="ViewModel"/> property.
@@ -78,7 +78,7 @@ namespace Avalonia.ReactiveUI
         /// </summary>
         public IViewLocator? ViewLocator { get; set; }
 
-        Type IStyleable.StyleKey => typeof(TransitioningContentControl);
+        protected override Type StyleKeyOverride => typeof(TransitioningContentControl);
 
         /// <summary>
         /// Invoked when ReactiveUI router navigates to a view model.
diff --git a/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github b/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github
index e5254eb1b2..c5d5d8b78d 160000
--- a/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github
+++ b/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github
@@ -1 +1 @@
-Subproject commit e5254eb1b2017f78a92acd466c8fa1e47401056b
+Subproject commit c5d5d8b78dce42dfb7b7f320a5c345da36a58579
diff --git a/src/Windows/Avalonia.Win32/TrayIconImpl.cs b/src/Windows/Avalonia.Win32/TrayIconImpl.cs
index d541e6b436..5069add9fd 100644
--- a/src/Windows/Avalonia.Win32/TrayIconImpl.cs
+++ b/src/Windows/Avalonia.Win32/TrayIconImpl.cs
@@ -170,9 +170,9 @@ namespace Avalonia.Win32
             WM_TRAYMOUSE = WindowsMessage.WM_USER + 1024,
         }
 
-        private class TrayIconMenuFlyoutPresenter : MenuFlyoutPresenter, IStyleable
+        private class TrayIconMenuFlyoutPresenter : MenuFlyoutPresenter
         {
-            Type IStyleable.StyleKey => typeof(MenuFlyoutPresenter);
+            protected override Type StyleKeyOverride => typeof(MenuFlyoutPresenter);
 
             public override void Close()
             {
diff --git a/tests/Avalonia.Base.UnitTests/AttachedPropertyTests.cs b/tests/Avalonia.Base.UnitTests/AttachedPropertyTests.cs
index f461240d68..8a6e7b8679 100644
--- a/tests/Avalonia.Base.UnitTests/AttachedPropertyTests.cs
+++ b/tests/Avalonia.Base.UnitTests/AttachedPropertyTests.cs
@@ -1,3 +1,4 @@
+using Avalonia.Controls;
 using Xunit;
 
 namespace Avalonia.Base.UnitTests
@@ -10,6 +11,7 @@ namespace Avalonia.Base.UnitTests
             var property = new AttachedProperty<string>(
                 "Foo",
                 typeof(Class1),
+                typeof(Control),
                 new StyledPropertyMetadata<string>());
 
             Assert.True(property.IsAttached);
diff --git a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Coercion.cs b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Coercion.cs
index fe4262331f..0d0456dbda 100644
--- a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Coercion.cs
+++ b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Coercion.cs
@@ -31,6 +31,16 @@ namespace Avalonia.Base.UnitTests
             Assert.Equal(100, target.GetValue(Class1.AttachedProperty));
         }
 
+        [Fact]
+        public void Coerces_Set_Value_Attached_On_Class_Not_Derived_From_Owner()
+        {
+            var target = new Class2();
+
+            target.SetValue(Class1.AttachedProperty, 150);
+
+            Assert.Equal(100, target.GetValue(Class1.AttachedProperty));
+        }
+
         [Fact]
         public void Coerces_Bound_Value()
         {
@@ -301,7 +311,7 @@ namespace Avalonia.Base.UnitTests
                     coerce: CoerceFoo);
 
             public static readonly AttachedProperty<int> AttachedProperty =
-                AvaloniaProperty.RegisterAttached<Class1, Class1, int>(
+                AvaloniaProperty.RegisterAttached<Class1, AvaloniaObject, int>(
                     "Attached",
                     defaultValue: 11,
                     coerce: CoerceFoo);
@@ -332,8 +342,9 @@ namespace Avalonia.Base.UnitTests
 
             public static int CoerceFoo(AvaloniaObject instance, int value)
             {
-                var o = (Class1)instance;
-                return Math.Clamp(value, o.MinFoo, o.MaxFoo);
+                return instance is Class1 o ? 
+                    Math.Clamp(value, o.MinFoo, o.MaxFoo) :
+                    Math.Clamp(value, 0, 100);
             }
 
             protected override void OnPropertyChangedCore(AvaloniaPropertyChangedEventArgs change)
diff --git a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Validation.cs b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Validation.cs
index 513aeb65ab..2b3bd07fed 100644
--- a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Validation.cs
+++ b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Validation.cs
@@ -15,6 +15,7 @@ namespace Avalonia.Base.UnitTests
                 new StyledProperty<int>(
                     "BadDefault",
                     typeof(Class1),
+                    typeof(Class1),
                     new StyledPropertyMetadata<int>(101),
                     validate: Class1.ValidateFoo));
         }
diff --git a/tests/Avalonia.Base.UnitTests/AvaloniaPropertyRegistryTests.cs b/tests/Avalonia.Base.UnitTests/AvaloniaPropertyRegistryTests.cs
index 0d62f20f7e..23e21c1645 100644
--- a/tests/Avalonia.Base.UnitTests/AvaloniaPropertyRegistryTests.cs
+++ b/tests/Avalonia.Base.UnitTests/AvaloniaPropertyRegistryTests.cs
@@ -22,7 +22,7 @@ namespace Avalonia.Base.UnitTests
         {
             var registry = new AvaloniaPropertyRegistry();
             var metadata = new StyledPropertyMetadata<int>();
-            var property = new AttachedProperty<int>("test", typeof(object), metadata, true);
+            var property = new AttachedProperty<int>("test", typeof(object), typeof(object), metadata, true);
             registry.Register(typeof(object), property);
             registry.RegisterAttached(typeof(AvaloniaPropertyRegistryTests), property);
             property.AddOwner<Class4>();
diff --git a/tests/Avalonia.Base.UnitTests/AvaloniaPropertyTests.cs b/tests/Avalonia.Base.UnitTests/AvaloniaPropertyTests.cs
index e44c15d962..d974351b1e 100644
--- a/tests/Avalonia.Base.UnitTests/AvaloniaPropertyTests.cs
+++ b/tests/Avalonia.Base.UnitTests/AvaloniaPropertyTests.cs
@@ -157,7 +157,7 @@ namespace Avalonia.Base.UnitTests
         private class TestProperty<TValue> : AvaloniaProperty<TValue>
         {
             public TestProperty(string name, Type ownerType, TestMetadata metadata = null)
-                : base(name, ownerType, metadata ?? new TestMetadata())
+                : base(name, ownerType, ownerType, metadata ?? new TestMetadata())
             {
             }
 
diff --git a/tests/Avalonia.Base.UnitTests/StyledPropertyTests.cs b/tests/Avalonia.Base.UnitTests/StyledPropertyTests.cs
index f0aa47784d..5304c74c39 100644
--- a/tests/Avalonia.Base.UnitTests/StyledPropertyTests.cs
+++ b/tests/Avalonia.Base.UnitTests/StyledPropertyTests.cs
@@ -9,7 +9,8 @@ namespace Avalonia.Base.UnitTests
         {
             var p1 = new StyledProperty<string>(
                 "p1", 
-                typeof(Class1), 
+                typeof(Class1),
+                typeof(Class1),
                 new StyledPropertyMetadata<string>());
             var p2 = p1.AddOwner<Class2>();
 
@@ -24,6 +25,7 @@ namespace Avalonia.Base.UnitTests
             var p1 = new StyledProperty<string>(
                 "p1",
                 typeof(Class1),
+                typeof(Class1),
                 new StyledPropertyMetadata<string>());
             var p2 = p1.AddOwner<Class2>();
 
diff --git a/tests/Avalonia.Base.UnitTests/Utilities/AvaloniaPropertyDictionaryTests.cs b/tests/Avalonia.Base.UnitTests/Utilities/AvaloniaPropertyDictionaryTests.cs
index 362eee8035..4b4aeb4344 100644
--- a/tests/Avalonia.Base.UnitTests/Utilities/AvaloniaPropertyDictionaryTests.cs
+++ b/tests/Avalonia.Base.UnitTests/Utilities/AvaloniaPropertyDictionaryTests.cs
@@ -18,6 +18,7 @@ namespace Avalonia.Base.UnitTests.Utilities
                 TestProperties[i] = new StyledProperty<string>(
                     $"Test{i}",
                     typeof(AvaloniaPropertyDictionaryTests),
+                    typeof(AvaloniaPropertyDictionaryTests),
                     new StyledPropertyMetadata<string>());
             }
 
diff --git a/tests/Avalonia.Benchmarks/Utilities/AvaloniaPropertyDictionaryBenchmarks.cs b/tests/Avalonia.Benchmarks/Utilities/AvaloniaPropertyDictionaryBenchmarks.cs
index e160c8dfa8..ef21100d1f 100644
--- a/tests/Avalonia.Benchmarks/Utilities/AvaloniaPropertyDictionaryBenchmarks.cs
+++ b/tests/Avalonia.Benchmarks/Utilities/AvaloniaPropertyDictionaryBenchmarks.cs
@@ -172,7 +172,7 @@ internal sealed class AvaloniaPropertyValueStoreOld<TValue>
 
 internal class MockProperty : StyledProperty<int>
 {
-    public MockProperty(string name) : base(name, typeof(object), new StyledPropertyMetadata<int>())
+    public MockProperty(string name) : base(name, typeof(object), typeof(object), new StyledPropertyMetadata<int>())
     {
     }
 }
diff --git a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
index 3d4852c4ff..86249c66ff 100644
--- a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
@@ -1031,9 +1031,9 @@ namespace Avalonia.Controls.UnitTests
                     textShaperImpl: new HeadlessTextShaperStub()));
         }
 
-        private class ItemsControlWithContainer : ItemsControl, IStyleable
+        private class ItemsControlWithContainer : ItemsControl
         {
-            Type IStyleable.StyleKey => typeof(ItemsControl);
+            protected override Type StyleKeyOverride => typeof(ItemsControl);
 
             protected internal override Control CreateContainerForItemOverride(object? item, int index, object? recycleKey)
             {
@@ -1046,9 +1046,9 @@ namespace Avalonia.Controls.UnitTests
             }
         }
 
-        private class ContainerControl : ContentControl, IStyleable
+        private class ContainerControl : ContentControl
         {
-            Type IStyleable.StyleKey => typeof(ContentControl);
+            protected override Type StyleKeyOverride => typeof(ContentControl);
         }
 
         private record Item(string Caption, string? Value = null);
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
index 9d2ffb1fa2..51745e1687 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
@@ -2160,6 +2160,45 @@ namespace Avalonia.Controls.UnitTests.Primitives
             }
         }
 
+        [Fact]
+        public void Does_Not_Write_To_Bound_SelectedItem_When_DataContext_Changes()
+        {
+            // Issue #9438.
+            var vm1 = new SelectionViewModel();
+            vm1.Items.Add("foo");
+            vm1.Items.Add("bar");
+            vm1.SelectedItem = "bar";
+
+            var vm2 = new SelectionViewModel();
+            vm2.Items.Add("foo");
+            vm2.Items.Add("bar");
+            vm2.SelectedItem = "bar";
+
+            var target = new SelectingItemsControl
+            {
+                DataContext = vm1,
+                [!ItemsControl.ItemsSourceProperty] = new Binding("Items"),
+                [!SelectingItemsControl.SelectedItemProperty] = new Binding("SelectedItem"),
+                Template = Template(),
+            };
+
+            Assert.Equal("bar", target.SelectedItem);
+            Assert.Equal(1, target.SelectedIndex);
+
+            var selectedItemChangedRaised = 0;
+            vm2.PropertyChanged += (s, e) =>
+            {
+                if (e.PropertyName == nameof(vm2.SelectedItem))
+                {
+                    ++selectedItemChangedRaised;
+                }
+            };
+
+            target.DataContext = vm2;
+
+            Assert.Equal(0, selectedItemChangedRaised);
+        }
+
         private static IDisposable Start()
         {
             return UnitTestApplication.Start(TestServices.StyledWindow);
@@ -2238,6 +2277,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         private class SelectionViewModel : NotifyingBase
         {
             private int _selectedIndex = -1;
+            private object _selectedItem;
 
             public SelectionViewModel()
             {
@@ -2255,6 +2295,16 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 }
             }
 
+            public object SelectedItem
+            {
+                get => _selectedItem;
+                set
+                {
+                    _selectedItem = value;
+                    RaisePropertyChanged();
+                }
+            }
+
             public ObservableCollection<string> Items { get; }
             public ObservableCollection<string> SelectedItems { get; }
         }
@@ -2267,6 +2317,9 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
         private class TestSelector : SelectingItemsControl
         {
+            public new static readonly DirectProperty<SelectingItemsControl, IList> SelectedItemsProperty =
+                SelectingItemsControl.SelectedItemsProperty;
+
             public TestSelector()
             {
                 
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
index 78ac6bb3e2..a4181fa8e8 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
@@ -1392,9 +1392,9 @@ namespace Avalonia.Controls.UnitTests.Primitives
             public void Toggle(int index) => UpdateSelection(index, true, false, true);
         }
 
-        private class TestSelectorWithContainers : TestSelector, IStyleable
+        private class TestSelectorWithContainers : TestSelector
         {
-            Type IStyleable.StyleKey => typeof(TestSelector);
+            protected override Type StyleKeyOverride => typeof(TestSelector);
 
             protected internal override Control CreateContainerForItemOverride(object? item, int index, object? recycleKey)
             {
diff --git a/tests/Avalonia.Controls.UnitTests/TabControlTests.cs b/tests/Avalonia.Controls.UnitTests/TabControlTests.cs
index 15ba871e8c..0d3eb80ae7 100644
--- a/tests/Avalonia.Controls.UnitTests/TabControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TabControlTests.cs
@@ -603,9 +603,9 @@ namespace Avalonia.Controls.UnitTests
             public string Value { get; }
         }
 
-        private class TestTabControl : TabControl, IStyleable
+        private class TestTabControl : TabControl
         {
-            Type IStyleable.StyleKey => typeof(TabControl);
+            protected override Type StyleKeyOverride => typeof(TabControl);
             public new ISelectionModel Selection => base.Selection;
         }
     }
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Converters/AvaloniaPropertyConverterTest.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Converters/AvaloniaPropertyConverterTest.cs
index d4d188f584..241ebc2d38 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Converters/AvaloniaPropertyConverterTest.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Converters/AvaloniaPropertyConverterTest.cs
@@ -1,12 +1,10 @@
 using System;
-using Moq;
-using Avalonia.Collections;
+using System.ComponentModel;
 using Avalonia.Markup.Xaml.Converters;
+using Avalonia.Markup.Xaml.XamlIl.Runtime;
 using Avalonia.Styling;
+using Moq;
 using Xunit;
-using System.ComponentModel;
-using Avalonia.Markup.Xaml.XamlIl.Runtime;
-using System.Collections.Generic;
 
 namespace Avalonia.Markup.Xaml.UnitTests.Converters
 {
@@ -112,61 +110,17 @@ namespace Avalonia.Markup.Xaml.UnitTests.Converters
             return tdMock.Object;
         }
 
-        private class Class1 : AvaloniaObject, IStyleable
+        private class Class1 : StyledElement
         {
             public static readonly StyledProperty<string> FooProperty =
                 AvaloniaProperty.Register<Class1, string>("Foo");
 
-            public IAvaloniaReadOnlyList<string> Classes
-            {
-                get { throw new NotImplementedException(); }
-            }
-
-            public string Name
-            {
-                get { throw new NotImplementedException(); }
-            }
-
-            public Type StyleKey
-            {
-                get { throw new NotImplementedException(); }
-            }
-
-            public AvaloniaObject TemplatedParent
-            {
-                get { throw new NotImplementedException(); }
-            }
-
-            public ControlTheme GetEffectiveTheme()
-            {
-                throw new NotImplementedException();
-            }
-
             public ThemeVariant ThemeVariant 
             {
                 get { throw new NotImplementedException(); }
             }
-            public event EventHandler ThemeVariantChanged;
-
-            public void DetachStyles()
-            {
-                throw new NotImplementedException();
-            }
 
-            public void DetachStyles(IReadOnlyList<IStyle> styles)
-            {
-                throw new NotImplementedException();
-            }
-
-            public void InvalidateStyles()
-            {
-                throw new NotImplementedException();
-            }
-
-            public void StyleApplied(IStyleInstance instance)
-            {
-                throw new NotImplementedException();
-            }
+            public event EventHandler ThemeVariantChanged;
         }
 
         private class AttachedOwner