Add WinRT removal breaking change (#19086)

* fixes #18875

* add interop to toc

docs/core/compatibility/3.1-5.0.md

@@ -101,6 +101,14 @@ If you're migrating from version 3.1 of .NET Core, ASP.NET Core, or EF Core to v
 
 ***
 
+## Interop
+
+- [Built-in support for WinRT is removed from .NET](#built-in-support-for-winrt-is-removed-from-net)
+
+[!INCLUDE [built-in-support-for-winrt-removed](~/includes/core-changes/interop/5.0/built-in-support-for-winrt-removed.md)]
+
+***
+
 ## Windows Forms
 
 - [Removed status bar controls](#removed-status-bar-controls)

docs/core/compatibility/interop.md

@@ -0,0 +1,18 @@
+---
+title: Interop breaking changes
+description: Lists the breaking changes in interop in .NET Core and .NET 5.0 and later.
+ms.date: 06/23/2020
+---
+# Interop breaking changes
+
+The following breaking changes are documented on this page:
+
+| Breaking change | Version introduced |
+| - | :-: |
+| [Built-in support for WinRT is removed from .NET](#built-in-support-for-winrt-is-removed-from-net) | 5.0 |
+
+## .NET 5.0
+
+[!INCLUDE [built-in-support-for-winrt-removed](~/includes/core-changes/interop/5.0/built-in-support-for-winrt-removed.md)]
+
+***

docs/core/compatibility/toc.yml

@@ -38,6 +38,8 @@
     href: /ef/core/what-is-new/ef-core-3.0/breaking-changes?toc=/dotnet/core/compatibility/toc.json&bc=/dotnet/breadcrumb/toc.json
   - name: Globalization
     href: globalization.md
+  - name: Interop
+    href: interop.md
   - name: MSBuild
     href: msbuild.md
   - name: Networking

includes/core-changes/categoryselector.md

@@ -5,6 +5,7 @@
 > - [Cryptography](~/docs/core/compatibility/cryptography.md)
 > - [EF Core](/ef/core/what-is-new/ef-core-3.0/breaking-changes)
 > - [Globalization](~/docs/core/compatibility/globalization.md)
+> - [Interop](~/docs/core/compatibility/interop.md)
 > - [Networking](~/docs/core/compatibility/networking.md)
 > - [Visual Basic](~/docs/core/compatibility/visualbasic.md)
 > - [Windows Forms](~/docs/core/compatibility/winforms.md)

includes/core-changes/interop/5.0/built-in-support-for-winrt-removed.md

@@ -0,0 +1,54 @@
+### Built-in support for WinRT is removed from .NET
+
+Built-in support for consumption of [Windows runtime (WinRT)](/uwp/winrt-cref/winrt-type-system) APIs in .NET is removed.
+
+#### Version introduced
+
+5.0 Preview 6
+
+#### Change description
+
+Previously, CoreCLR could consume [Windows metadata (WinMD) files](/uwp/winrt-cref/winmd-files) to active and consume WinRT types. Starting in .NET 5.0, CoreCLR can no longer consume WinMD files directly.
+
+If you attempt to reference an unsupported assembly, you'll get a <xref:System.IO.FileNotFoundException>. If you activate a WinRT class, you'll get a <xref:System.PlatformNotSupportedException>.
+
+This breaking change was made for the following reasons:
+
+- So WinRT can be developed and improved separately from the .NET runtime.
+- For symmetry with interop systems provided for other operating systems, such as iOS and Android.
+- To take advantage of other .NET features, such as C# features, intermediate language (IL) linking, and ahead-of-time (AOT) compilation.
+- To simplify the .NET runtime codebase.
+
+#### Recommended action
+
+- Remove references to the [Microsoft.Windows.SDK.Contracts package](https://www.nuget.org/packages/Microsoft.Windows.SDK.Contracts) and replace them with references to the [Microsoft.Windows.SDK.NET package](https://www.nuget.org/packages/microsoft.windows.sdk.net).
+
+- Use the [C#/WinRT](/windows/uwp/csharp-winrt/) tool chain to generate or customize WinRT APIs and types in .NET 5.0 and later versions.
+
+#### Category
+
+Interop
+
+#### Affected APIs
+
+- <xref:System.IO.WindowsRuntimeStorageExtensions?displayProperty=fullName>
+- <xref:System.IO.WindowsRuntimeStreamExtensions?displayProperty=fullName>
+- <xref:System.Runtime.InteropServices.WindowsRuntime?displayProperty=fullName>
+- <xref:System.WindowsRuntimeSystemExtensions?displayProperty=fullName>
+- <xref:Windows.Foundation.Point?displayProperty=fullName>
+- <xref:Windows.Foundation.Size?displayProperty=fullName>
+- <xref:Windows.UI.Color?displayProperty=fullName>
+
+<!--
+
+#### Affected APIs
+
+- `T:System.IO.WindowsRuntimeStorageExtensions`
+- `T: System.IO.WindowsRuntimeStreamExtensions`
+- `N:System.Runtime.InteropServices.WindowsRuntime`
+- `T:System.WindowsRuntimeSystemExtensions`
+- `T:Windows.Foundation.Point`
+- `T:Windows.Foundation.Size`
+- `T:Windows.UI.Color`
+
+-->