Update sdk.md (#13963)

aspnetcore/razor-pages/sdk.md

@@ -16,8 +16,16 @@ By [Rick Anderson](https://twitter.com/RickAndMSFT)
 
 The [!INCLUDE[](~/includes/2.1-SDK.md)] includes the `Microsoft.NET.Sdk.Razor` MSBuild SDK (Razor SDK). The Razor SDK:
 
+::: moniker range=">= aspnetcore-2.1 <= aspnetcore-2.2"
 * Standardizes the experience around building, packaging, and publishing projects containing [Razor](xref:mvc/views/razor) files for ASP.NET Core MVC-based projects.
 * Includes a set of predefined targets, properties, and items that allow customizing the compilation of Razor files.
+::: moniker-end
+
+::: moniker range=">= aspnetcore-3.0"
+* is required to build, package, and publish projects containing [Razor](xref:mvc/views/razor) files for ASP.NET Core MVC-based projects, or [Blazor](xref:blazor/index) projects
+* Includes a set of predefined targets, properties, and items that allow customizing the compilation of Razor (.cshtml or .razor) files.
+::: moniker-end
+
 
 ::: moniker range=">= aspnetcore-2.1 <= aspnetcore-2.2"
 
@@ -39,6 +47,7 @@ The Razor SDK includes `<Content>` elements with `Include` attributes set to the
 
 Most web apps aren't required to explicitly reference the Razor SDK.
 
+::: moniker range=">= aspnetcore-2.1 <= aspnetcore-2.2"
 To use the Razor SDK to build class libraries containing Razor views or Razor Pages:
 
 * Use `Microsoft.NET.Sdk.Razor` instead of `Microsoft.NET.Sdk`:
@@ -60,6 +69,13 @@ To use the Razor SDK to build class libraries containing Razor views or Razor Pa
   The preceding packages are included in `Microsoft.AspNetCore.Mvc`. The following markup shows a project file that uses the Razor SDK to build Razor files for an ASP.NET Core Razor Pages app:
     
   [!code-xml[](sdk/sample/RazorSDK.csproj)]
+  
+::: moniker-end
+
+::: moniker range=">= aspnetcore-3.0"
+To use the Razor SDK to build class libraries containing Razor views or Razor Pages we recommend starting with the Razor Class Library project template. A Razor class library that is used to build Blazor (.razor) files will at minimum require a reference to the `Microsoft.AspNetCore.Components` package. A Razor class library that is used to build Razor views or pages (.cshtml files), will require targeting `netcoreapp3.0` or newer and have a `FrameworkReference` to `Microsoft.AspNetCore.App`.
+
+::: moniker-end
 
 ::: moniker range="= aspnetcore-2.1"
 
@@ -77,9 +93,16 @@ The following properties control the Razor's SDK behavior as part of a project b
 
 The properties and items in the following table are used to configure inputs and output to the Razor SDK.
 
+::: moniker range=">= aspnetcore-3.0"
+> [!WARNING]
+Starting with ASP.NET Core 3.0, MVC Views or Razor Pages will not be served by default if `RazorCompileOnBuild` or `RazorCompileOnPublish` is disabled. Applications must add an explicit reference to `Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation` package to add support for runtime compilation if they rely on runtime compilation to process cshtml files.
+::: moniker-end
+
+
 | Items | Description |
 | ----- | ----------- |
-| `RazorGenerate` | Item elements (*.cshtml* files) that are inputs to code generation targets. |
+| `RazorGenerate` | Item elements (*.cshtml* files) that are inputs to code generation. |
+| `RazorComponent` | Item elements (*.razor* files) that are inputs to Component code generation.
 | `RazorCompile` | Item elements (*.cs* files) that are inputs to Razor compilation targets. Use this `ItemGroup` to specify additional files to be compiled into the Razor assembly. |
 | `RazorTargetAssemblyAttribute` | Item elements used to code generate attributes for the Razor assembly. For example:  <br>`RazorAssemblyAttribute`<br>`Include="System.Reflection.AssemblyMetadataAttribute"`<br>`_Parameter1="BuildSource" _Parameter2="https://docs.microsoft.com/">` |
 | `RazorEmbeddedResource` | Item elements added as embedded resources to the generated Razor assembly. |
@@ -98,6 +121,7 @@ The properties and items in the following table are used to configure inputs and
 | `IncludeRazorContentInPack` | When `true`, all Razor content items (*.cshtml* files) are marked for inclusion in the generated NuGet package. Defaults to `false`. |
 | `EmbedRazorGenerateSources` | When `true`, adds RazorGenerate (*.cshtml*) items as embedded files to the generated Razor assembly. Defaults to `false`. |
 | `UseRazorBuildServer` | When `true`, uses a persistent build server process to offload code generation work. Defaults to the value of `UseSharedCompilation`. |
+| `GenerateMvcApplicationPartsAssemblyAttributes` | When `true`, the SDK generates additional attributes used by MVC at runtime to perform application part discovery. |
 
 For more information on properties, see [MSBuild properties](/visualstudio/msbuild/msbuild-properties).
 
@@ -107,6 +131,7 @@ The Razor SDK defines two primary targets:
 
 * `RazorGenerate` &ndash; Code generates *.cs* files from `RazorGenerate` item elements. Use `RazorGenerateDependsOn` property to specify additional targets that can run before or after this target.
 * `RazorCompile` &ndash; Compiles generated *.cs* files in to a Razor assembly. Use `RazorCompileDependsOn` to specify additional targets that can run before or after this target.
+* `RazorComponentGenerate` &ndash; Code generates *.cs* files for `RazorComponent` item elements. Use `RazorComponentGenerateDependsOn` property to specify additional targets that can run before or after this target.
 
 ### Runtime compilation of Razor views
 
@@ -124,6 +149,8 @@ When targeting the `Microsoft.NET.Sdk.Web` SDK, the Razor language version is in
 </PropertyGroup>
 ```
 
+Razor's language version is tightly integrated with the version of the runtime that it was built for. Targeting a language version that is not designed for the runtime is unsupported, and will likely produce build errors.
+
 ## Additional resources
 
 * [Additions to the csproj format for .NET Core](/dotnet/core/tools/csproj)