MarkupExtension use interface instead of abstract class

src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Windows/Markup/IMarkupExtension.cs

@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Runtime.CompilerServices;
+
+namespace System.Windows.Markup
+{
+    /// <summary>
+    /// Base interface for all Xaml markup extensions.
+    /// </summary>
+    public interface IMarkupExtension
+    {
+        /// <summary>
+        ///  Return an object that should be set on the targetObject's targetProperty
+        ///  for this markup extension.  
+        /// </summary>
+        /// <param name="serviceProvider">Object that can provide services for the markup extension.</param>
+        /// <returns>
+        ///  The object to set on this property.
+        /// </returns>
+        object ProvideValue(IServiceProvider serviceProvider);
+    }
+}

src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Windows/Markup/MarkupExtension.cs

@@ -11,7 +11,7 @@ namespace System.Windows.Markup
     ///  be instantiated.
     /// </summary>
     [TypeForwardedFrom("WindowsBase, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35")]
-    public abstract class MarkupExtension 
+    public abstract class MarkupExtension : IMarkupExtension
     {
         /// <summary>
         ///  Return an object that should be set on the targetObject's targetProperty

src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Windows/Markup/XamlSetMarkupExtensionEventArgs.cs

@@ -9,17 +9,17 @@ namespace System.Windows.Markup
     public class XamlSetMarkupExtensionEventArgs : XamlSetValueEventArgs
     {
         public XamlSetMarkupExtensionEventArgs(XamlMember member,
-            MarkupExtension value, IServiceProvider serviceProvider) :
+            IMarkupExtension value, IServiceProvider serviceProvider) :
             base(member, value)
         {
             ServiceProvider = serviceProvider;
         }
 
-        public MarkupExtension MarkupExtension { get { return Value as MarkupExtension; } }
+        public IMarkupExtension MarkupExtension { get { return Value as IMarkupExtension; } }
         public IServiceProvider ServiceProvider { get; private set; }
 
         internal XamlSetMarkupExtensionEventArgs(XamlMember member,
-            MarkupExtension value, IServiceProvider serviceProvider, object targetObject)
+            IMarkupExtension value, IServiceProvider serviceProvider, object targetObject)
             : this(member, value, serviceProvider)
         {
             TargetObject = targetObject;

src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/Context/ObjectWriterContext.cs

@@ -383,7 +383,7 @@ private List<AmbientPropertyValue> FindAmbientValues(IEnumerable<XamlType> ceili
                                     // One last thing to check:  If the object we are inside is a ME
                                     // then we are inside a call to ProvideValue and we don't want to
                                     // return a reference to ourselves to ourselves.
-                                    if (!(lowerFrame.Instance is XAML3.MarkupExtension))
+                                    if (!(lowerFrame.Instance is XAML3.IMarkupExtension))
                                     {
                                         returnAmbientValue = true;
                                         value = lowerFrame.Instance;

src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/InfosetObjects/XamlObjectWriter.cs

@@ -779,7 +779,7 @@ public override void WriteEndMember()
                 bool shouldSetValue = true;
                 if (value != null)
                 {
-                    XAML3.MarkupExtension me = value as XAML3.MarkupExtension;
+                    XAML3.IMarkupExtension me = value as XAML3.IMarkupExtension;
                     if (me != null)
                     {
                         _context.CurrentInstance = me;
@@ -1156,7 +1156,7 @@ private void Logic_CreateAndAssignToParentStart(ObjectWriterContext ctx)
                 object[] args = ctx.CurrentCtorArgs;
                 for (int i = 0; i < args.Length; i++)
                 {
-                    XAML3.MarkupExtension me = args[i] as XAML3.MarkupExtension;
+                    XAML3.IMarkupExtension me = args[i] as XAML3.IMarkupExtension;
                     if (me != null)
                     {
                         args[i] = Logic_PushAndPopAProvideValueStackFrame(ctx, XamlLanguage.PositionalParameters, me, false);
@@ -1216,7 +1216,7 @@ private void Logic_CreateAndAssignToParentStart(ObjectWriterContext ctx)
             // If UsableDuringInit, Assign to parent
             // We don't want to assign MEs to the parent since we need to call ProvideValue on them
             //   which is handled in WriteEndObject
-            if (ctx.LiveDepth > 1 && !(inst is XAML3.MarkupExtension))
+            if (ctx.LiveDepth > 1 && !(inst is XAML3.IMarkupExtension))
             {
                 if (ctx.LiveDepth > 1)
                 {
@@ -1565,7 +1565,7 @@ private void Logic_ApplyCurrentPreconstructionPropertyValues(ObjectWriterContext
                     // so don't call ProvideValue() now on directives here.
                     // (x:Key and x:Name need their own "saved spot" outside of PreconstructionPropertyValues)
 
-                    XAML3.MarkupExtension me = value as XAML3.MarkupExtension;
+                    XAML3.IMarkupExtension me = value as XAML3.IMarkupExtension;
                     if (me != null && !prop.IsDirective)
                     {
                         Logic_PushAndPopAProvideValueStackFrame(ctx, prop, me, true);
@@ -1578,7 +1578,7 @@ private void Logic_ApplyCurrentPreconstructionPropertyValues(ObjectWriterContext
             }
         }
 
-        private object Logic_PushAndPopAProvideValueStackFrame(ObjectWriterContext ctx, XamlMember prop, XAML3.MarkupExtension me, bool useIRME)
+        private object Logic_PushAndPopAProvideValueStackFrame(ObjectWriterContext ctx, XamlMember prop, XAML3.IMarkupExtension me, bool useIRME)
         {
             XamlMember savedProp = ctx.CurrentProperty;
             ctx.CurrentProperty = prop;
@@ -1689,7 +1689,7 @@ private void Logic_AssignProvidedValue(ObjectWriterContext ctx)
         private bool Logic_ProvideValue(ObjectWriterContext ctx)
         {
             object inst = ctx.CurrentInstance;
-            XAML3.MarkupExtension me = (XAML3.MarkupExtension)inst;
+            XAML3.IMarkupExtension me = (XAML3.IMarkupExtension)inst;
             object parentInstance = ctx.ParentInstance;
             XamlMember parentProperty = ctx.ParentProperty;
 
@@ -1806,7 +1806,7 @@ private void Logic_DoAssignmentToParentCollection(ObjectWriterContext ctx)
                 {
                     // If Value is a Markup Extention then check the collection item type
                     // if it can hold the ME then don't call ProvideValue().
-                    XAML3.MarkupExtension me = value as XAML3.MarkupExtension;
+                    XAML3.IMarkupExtension me = value as XAML3.IMarkupExtension;
                     if(me != null && !Logic_WillParentCollectionAdd(ctx, value.GetType(), true))
                     {
                         // We don't need to call Logic_ProvideValue() with the extra handler
@@ -2516,7 +2516,7 @@ private void ProcessNameFixup_Reparse(NameFixupToken token, bool nameResolutionI
                     break;
                 case FixupType.MarkupExtensionRerun:
                     // Logic_ProvideValue already ran the first time, no need to rerun it
-                    value = Runtime.CallProvideValue((XAML3.MarkupExtension)owc.CurrentInstance, owc.ServiceProviderContext);
+                    value = Runtime.CallProvideValue((XAML3.IMarkupExtension)owc.CurrentInstance, owc.ServiceProviderContext);
                     owc.CurrentInstance = value;
                     break;
                 case FixupType.PropertyValue:

src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/Runtime/ClrObjectRuntime.cs

@@ -478,7 +478,7 @@ public override void InitializationGuard(XamlType xamlType, object obj, bool beg
             }
         }
 
-        public override object CallProvideValue(XAML3.MarkupExtension me, IServiceProvider serviceProvider)
+        public override object CallProvideValue(XAML3.IMarkupExtension me, IServiceProvider serviceProvider)
         {
             try
             {

src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/Runtime/PartialTrustTolerantRuntime.cs

@@ -68,7 +68,7 @@ public override void AddToDictionary(object collection, XamlType dictionaryType,
             _transparentRuntime.AddToDictionary(collection, dictionaryType, value, valueXamlType, key);
         }
 
-        public override object CallProvideValue(MarkupExtension me, IServiceProvider serviceProvider)
+        public override object CallProvideValue(IMarkupExtension me, IServiceProvider serviceProvider)
         {
             // Once the ME is instantiated, invocation is always a public method call
             return _transparentRuntime.CallProvideValue(me, serviceProvider);

src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/XamlLanguage.cs

@@ -90,7 +90,7 @@ public static class XamlLanguage
             new Lazy<XamlType>(() => GetXamlType(typeof(List<Attribute>)));
         // These aren't language built-ins, but we use them in schema
         private static Lazy<XamlType> s_markupExtension =
-            new Lazy<XamlType>(() => GetXamlType(typeof(MarkupExtension)));
+            new Lazy<XamlType>(() => GetXamlType(typeof(IMarkupExtension)));
         private static Lazy<XamlType> s_iNameScope =
             new Lazy<XamlType>(() => GetXamlType(typeof(INameScope)));
         private static Lazy<XamlType> s_iXmlSerializable =

src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/XamlObjectReader.cs

@@ -1351,7 +1351,7 @@ bool TryAddPositionalParameters(XamlType xamlType, MemberInfo member, ICollectio
                             context.Instance = null;
                             positionalParametersProperty.Children.Add(new ValueMarkupInfo { XamlNode = new XamlNode(XamlNodeType.Value, stringValue) });
                         }
-                        else if ((converter != null && context.TryConvertToMarkupExtension(converter, ref meObject)) || meObject is MarkupExtension)
+                        else if ((converter != null && context.TryConvertToMarkupExtension(converter, ref meObject)) || meObject is IMarkupExtension)
                         {
                             context.Instance = null;
                             objectInfo = ForObject(meObject, context);
@@ -2725,9 +2725,9 @@ public bool TryTypeConvertToString(TypeConverter converter, ref object value)
             public bool TryConvertToMarkupExtension(TypeConverter converter, ref object value)
             {
                 if (value == null) { return false; }
-                if (!Runtime.CanConvertTo(TypeDescriptorContext, converter, typeof(MarkupExtension))) { return false; }
+                if (!Runtime.CanConvertTo(TypeDescriptorContext, converter, typeof(IMarkupExtension))) { return false; }
 
-                value = ConvertTo<MarkupExtension>(converter, value);
+                value = ConvertTo<IMarkupExtension>(converter, value);
                 return true;
             }
 

src/Microsoft.DotNet.Wpf/src/System.Xaml/System/Xaml/XamlRuntime.cs

@@ -76,7 +76,7 @@ public object GetValue(object obj, XamlMember property)
 
         abstract public void InitializationGuard(XamlType xamlType, object obj, bool begin);
 
-        abstract public object CallProvideValue(MarkupExtension me, IServiceProvider serviceProvider);
+        abstract public object CallProvideValue(IMarkupExtension me, IServiceProvider serviceProvider);
 
         abstract public ShouldSerializeResult ShouldSerialize(XamlMember member, object instance);