Update xaml-designer-extensibility-migration.md

Author: lutzroeder

docs/extensibility/xaml-designer-extensibility-migration.md

@@ -12,7 +12,7 @@ monikerRange: vs-2019
 ---
 # XAML designer extensibility migration
 
-Starting in Visual Studio 2019 version 16.1 as a public preview, the XAML designer supports two different architectures: the designer isolation architecture and the more recent surface isolation architecture. This architecture transition is required to support target runtimes that can't be hosted in a .NET Framework process. Moving to the surface isolation architecture introduces breaking changes to the third-party extensibility model. This article outlines the changes.
+In Visual Studio 2019, the XAML designer supports two different architectures: the designer isolation architecture and the more recent surface isolation architecture. This architecture transition is required to support target runtimes that can't be hosted in a .NET Framework process. Moving to the surface isolation architecture introduces breaking changes to the third-party extensibility model. This article outlines these changes which are available in the Visual Studio 2019 16.2 preview channel.
 
 **Designer isolation** is used by the WPF designer for projects that target the .NET Framework and supports *.design.dll* extensions. User code, control libraries, and third-party extensions are loaded in an external process (*XDesProc.exe*) along with the actual designer code and designer panels.
 
@@ -41,7 +41,7 @@ While third-party control libraries are compiled for the actual target runtime (
 
 The surface isolation extensibility model doesn't allow for extensions to depend on actual control libraries, and therefore, extensions can't reference types from the control library. For example, *MyLibrary.designtools.dll* should not have a dependency on *MyLibrary.dll*.
 
-Such dependencies were most common when registering metadata for types via attribute tables. Extension code that references control library types directly via [typeof](/dotnet/csharp/language-reference/keywords/typeof) ([GetType](/dotnet/visual-basic/language-reference/operators/gettype-operator) in Visual Basic) is substituted in the new APIs by using string-based type names:
+Such dependencies were most common when registering metadata for types via attribute tables. Extension code that references control library types directly via [typeof](/dotnet/csharp/language-reference/keywords/typeof) or [GetType](/dotnet/visual-basic/language-reference/operators/gettype-operator) is substituted in the new APIs by using string-based type names:
 
 ```csharp
 using Microsoft.VisualStudio.DesignTools.Extensibility.Metadata;
@@ -56,7 +56,7 @@ public class AttributeTableProvider : IProvideAttributeTable
   {
     get
     {
-      AttributeTableBuilder builder = new AttributeTableBuilder();
+      var builder = new AttributeTableBuilder();
       builder.AddCustomAttributes("MyLibrary.MyControl", new DescriptionAttribute(Strings.MyControlDescription);
       builder.AddCustomAttributes("MyLibrary.MyControl", new FeatureAttribute(typeof(MyControlDefaultInitializer));
       return builder.CreateTable();
@@ -90,6 +90,14 @@ End Class
 
 Feature providers are implemented in extension assemblies and loaded in the Visual Studio process. `FeatureAttribute` will continue to reference feature provider types directly using [typeof](/dotnet/csharp/language-reference/keywords/typeof).
 
+Currently, the following feature providers are supported:
+
+* `DefaultInitializer`
+* `AdornerProvider`
+* `ContextMenuProvider`
+* `ParentAdapter`
+* `PlacementAdapter`
+
 Because feature providers are now loaded in a process different from the actual runtime code and control libraries, they are no longer able to access runtime objects directly. Instead, all such interactions must be converted to use the corresponding Model-based APIs. The Model API has been updated, and access to <xref:System.Type> or <xref:System.Object> is either no longer available or has been replaced with `TypeIdentifier` and `TypeDefinition`.
 
 `TypeIdentifier` represents a string without an assembly name identifying a type. A `TypeIdenfifier` can be resolved to a `TypeDefinition` to query additional information about the type. `TypeDefinition` instances can't be cached in extension code.
@@ -99,7 +107,7 @@ TypeDefinition type = ModelFactory.ResolveType(
     item.Context, new TypeIdentifier("MyLibrary.MyControl"));
 TypeDefinition buttonType = ModelFactory.ResolveType(
     item.Context, new TypeIdentifier("System.Windows.Controls.Button"));
-if (type != null && buttonType != type.IsSubclassOf(buttonType))
+if (type?.IsSubclassOf(buttonType) == true)
 {
 }
 ```
@@ -198,6 +206,8 @@ Public Class MyControlDefaultInitializer
 End Class
 ```
 
+More code samples are available in the [xaml-designer-extensibility-samples](https://github.com/microsoft/xaml-designer-extensibility-samples) repository.
+
 ## Limited support for .design.dll extensions
 
 If any *.designtools.dll* extension is discovered for a control library, it is loaded first and discovery for *.design.dll* extensions is skipped.