Update 3.1-to-5.0 migration guide for Preview 7 (#19288)

* Update 3.1-to-5.0 migration guide for Preview 7

* Update package refs section

aspnetcore/migration/31-to-50.md

@@ -4,7 +4,7 @@ author: scottaddie
 description: Learn how to migrate an ASP.NET Core 3.1 project to ASP.NET Core 5.0.
 ms.author: scaddie
 ms.custom: mvc
-ms.date: 06/11/2020
+ms.date: 07/22/2020
 no-loc: [Blazor, "Blazor Server", "Blazor WebAssembly", "Identity", "Let's Encrypt", Razor, SignalR]
 uid: migration/31-to-50
 ---
@@ -41,14 +41,14 @@ If you rely upon a [global.json](/dotnet/core/tools/global-json) file to target
 {
   "sdk": {
 -    "version": "3.1.200"
-+    "version": "5.0.100-preview.6.20318.15"
++    "version": "5.0.100-preview.7.20366.6"
   }
 }
 ```
 
 ## Update the target framework
 
-In the project file, update the [Target Framework Moniker (TFM)](/dotnet/standard/frameworks) to `net5.0`:
+If updating a Blazor WebAssembly project, skip to the [Update Blazor WebAssembly projects](#update-blazor-webassembly-projects) section. For any other ASP.NET Core project type, update the project file's [Target Framework Moniker (TFM)](/dotnet/standard/frameworks) to `net5.0`:
 
 ```diff
 <Project Sdk="Microsoft.NET.Sdk.Web">
@@ -61,16 +61,43 @@ In the project file, update the [Target Framework Moniker (TFM)](/dotnet/standar
 </Project>
 ```
 
+## Update Blazor WebAssembly projects
+
+For Blazor WebAssembly projects, apply the following changes in the project file:
+
+1. Update the following properties:
+
+    ```diff
+    <Project Sdk="Microsoft.NET.Sdk.Web">
+    
+      <PropertyGroup>
+    -     <TargetFramework>netstandard2.1</TargetFramework>
+    -     <RazorLangVersion>3.0</RazorLangVersion>
+    +     <TargetFramework>net5.0</TargetFramework>
+    +     <RuntimeIdentifier>browser-wasm</RuntimeIdentifier>
+    +     <UseBlazorWebAssembly>true</UseBlazorWebAssembly>
+      </PropertyGroup>
+    ```
+
+1. Remove the package reference to [Microsoft.AspNetCore.Components.WebAssembly.Build](https://www.nuget.org/packages/Microsoft.AspNetCore.Components.WebAssembly.Build):
+
+    ```diff
+    <ItemGroup>
+    -    <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.Build" Version="3.2.1" PrivateAssets="all" />
+    ```
+
 ## Update package references
 
-In the project file, update each `Microsoft.AspNetCore.*` and `Microsoft.Extensions.*` package reference's `Version` attribute to 5.0.0 or later. For example:
+In the project file, update each [Microsoft.AspNetCore.*](https://www.nuget.org/packages?q=Microsoft.AspNetCore.*), [Microsoft.Extensions.*](https://www.nuget.org/packages?q=Microsoft.Extensions.*), and [System.Net.Http.Json](https://www.nuget.org/packages/System.Net.Http.Json) package reference's `Version` attribute to 5.0.0 or later. For example:
 
 ```diff
 <ItemGroup>
--    <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" Version="3.1.2" />
--    <PackageReference Include="Microsoft.Extensions.Caching.Abstractions" Version="3.1.2" />
-+    <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" Version="5.0.0-preview.6.20312.15" />
-+    <PackageReference Include="Microsoft.Extensions.Caching.Abstractions" Version="5.0.0-preview.6.20305.6" />
+-    <PackageReference Include="Microsoft.AspNetCore.JsonPatch" Version="3.1.6" />
+-    <PackageReference Include="Microsoft.Extensions.Caching.Abstractions" Version="3.1.6" />
+-    <PackageReference Include="System.Net.Http.Json" Version="3.2.1" />
++    <PackageReference Include="Microsoft.AspNetCore.JsonPatch" Version="5.0.0-preview.7.20365.19" />
++    <PackageReference Include="Microsoft.Extensions.Caching.Abstractions" Version="5.0.0-preview.7.20364.11" />
++    <PackageReference Include="System.Net.Http.Json" Version="5.0.0-preview.7.20364.11" />
 </ItemGroup>
 ```