[One .NET] update user-facing messages from .NET 5 to .NET 6 (#5300)

Since 6f761ea gets us on a build of .NET 6, we can update all user-
facing messaging to say .NET 6 instead of .NET 5.

  * Documentation around building `xamarin-android`
  * Error/warning messages

I also updated a few things other things that should say .NET 6:

  * `NuGet.config` sources in MSBuild tests
  * `@(FrameworkListRootAttributes)` for our .NET 6 packages

I did not update various code comments, as most of them say .NET 5+
and are not user-facing.

Other changes in `OneDotNet.md`:

  * Started a new `Runtime behavior` section with a link to
    `string.IndexOf()` behavior.
  * Link to `net6-samples` as the source for .NET 6 example projects
    and installation instructions.

Author: jonathanpeppers

Documentation/building/unix/instructions.md

@@ -79,7 +79,7 @@ installer.
 
 # Creating a local .NET 6 Workload
 
-`make prepare` provisions a specific build of .NET 5/6 to
+`make prepare` provisions a specific build of .NET 6 to
 `~/android-toolchain/dotnet`.
 
 Once `make all` or `make jenkins` have completed, you can build the .NET 6
@@ -100,7 +100,6 @@ To use the Android workload, you will need a `NuGet.config`:
 <configuration>
   <packageSources>
     <add key="dotnet6" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet6/nuget/v3/index.json" />
-    <add key="dotnet5" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet5/nuget/v3/index.json" />
     <add key="local-xa" value="/full/path/to/bin/BuildDebug/nupkgs" />
   </packageSources>
 </configuration>

Documentation/building/windows/instructions.md

@@ -90,7 +90,7 @@ So for example:
 # Creating a local .NET 6 Workload
 
 `msbuild Xamarin.Android.sln /t:Prepare` provisions a specific build
-of .NET 5/6 to `%USERPROFILE%\android-toolchain\dotnet`.
+of .NET 6 to `%USERPROFILE%\android-toolchain\dotnet`.
 
 Once `msbuild Xamarin.Android.sln /t:Build` is complete, you can build
 the .NET 6 packages with:
@@ -110,7 +110,6 @@ To use the Android workload, you will need a `NuGet.config`:
 <configuration>
   <packageSources>
     <add key="dotnet6" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet6/nuget/v3/index.json" />
-    <add key="dotnet5" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet5/nuget/v3/index.json" />
     <add key="local-xa" value="C:\full\path\to\bin\BuildDebug\nupkgs" />
   </packageSources>
 </configuration>

Documentation/guides/OneDotNet.md

@@ -140,6 +140,13 @@ all default item inclusion behavior can be disabled by setting `$(EnableDefaultI
 
 [autoimport]: https://github.com/dotnet/designs/blob/4703666296f5e59964961464c25807c727282cae/accepted/2020/workloads/workload-resolvers.md#workload-props-files
 
+## Runtime behavior
+
+There is some behavioral changes to the `String.IndexOf()` method in
+.NET 5 and higher on different platforms, see details [here][indexof].
+
+[indexof]: https://docs.microsoft.com/dotnet/standard/globalization-localization/globalization-icu
+
 ## Linker (ILLink)
 
 .NET 5 and higher has new [settings for the linker][linker]:
@@ -220,39 +227,10 @@ device or emulator via the `--project` switch:
 
 ### Preview testing
 
-The following instructions can be used for early preview testing.
-
-  1) Install the [latest .NET 5 preview][0]. Preview 4 or later is required.
-
-  2) Create a `nuget.config` file that has a package source pointing to
-     local packages or `xamarin-impl` feed, as well as the .NET 5 feed:
-
-```xml
-<configuration>
-  <packageSources>
-    <add key="xamarin-impl" value="https://pkgs.dev.azure.com/azure-public/vside/_packaging/xamarin-impl/nuget/v3/index.json" />
-    <add key="dotnet5" value="https://dnceng.pkgs.visualstudio.com/public/_packaging/dotnet5/nuget/v3/index.json" />
-  </packageSources>
-</configuration>
-```
-
-  3) Open an existing Android project (ideally something minimal) and
-    tweak it as shown below. The version should match the version of the
-    packages you want to use:
-
-```xml
-<Project Sdk="Microsoft.Android.Sdk/10.0.100">
-  <PropertyGroup>
-    <TargetFramework>net6.0-android</TargetFramework>
-    <RuntimeIdentifier>android.21-arm64</RuntimeIdentifier>
-    <OutputType>Exe</OutputType>
-  </PropertyGroup>
-</Project>
-```
-
-  4) Build (and optionally run) the project:
+For the latest instructions on preview testing and sample projects,
+see the [net6-samples][net6-samples] repo.
 
-    dotnet build *.csproj -t:Run
+[net6-samples]: https://github.com/xamarin/net6-samples
 
 ## Package Versioning Scheme
 

Documentation/guides/messages/README.md

@@ -47,7 +47,7 @@ ms.date: 01/24/2020
 + [XA0033](xa0033.md): Failed to get the Java SDK version because the returned value does not appear to contain a valid version number.
 + [XA0034](xa0034.md): Failed to get the Java SDK version.
 + [XA0035](xa0035.md): Failed to determine the Android ABI for the project.
-+ [XA0036](xa0036.md): $(AndroidSupportedAbis) is not supported in .NET 5 and higher.
++ [XA0036](xa0036.md): $(AndroidSupportedAbis) is not supported in .NET 6 and higher.
 + XA0100: EmbeddedNativeLibrary is invalid in Android Application projects. Please use AndroidNativeLibrary instead.
 + [XA0101](xa0101.md): warning XA0101: @(Content) build action is not supported.
 + [XA0102](xa0102.md): Generic `lint` Warning.
@@ -105,13 +105,13 @@ Please disable fast deployment in the Visual Studio project property pages or ed
 + XA1021: Specified source Java library not found: {file}
 + XA1022: Specified reference Java library not found: {file}
 + [XA1023](xa1023.md): Using the DX DEX Compiler is deprecated.
-+ [XA1024](xa1024.md): Ignoring configuration file 'Foo.dll.config'. .NET configuration files are not supported in Xamarin.Android projects that target .NET 5 or higher.
++ [XA1024](xa1024.md): Ignoring configuration file 'Foo.dll.config'. .NET configuration files are not supported in Xamarin.Android projects that target .NET 6 or higher.
 + [XA1027](xa1027.md): The 'EnableProguard' MSBuild property is set to 'true' and the 'AndroidLinkTool' MSBuild property is empty, so 'AndroidLinkTool' will default to 'proguard'.
 + [XA1028](xa1028.md): The 'AndroidEnableProguard' MSBuild property is set to 'true' and the 'AndroidLinkTool' MSBuild property is empty, so 'AndroidLinkTool' will default to 'proguard'.
 
 ## XA2xxx: Linker
 
-+ [XA2000](xa2000.md): Use of AppDomain.CreateDomain() detected in assembly: {assembly}. .NET 5 will only support a single AppDomain, so this API will no longer be available in Xamarin.Android once .NET 5 is released.
++ [XA2000](xa2000.md): Use of AppDomain.CreateDomain() detected in assembly: {assembly}. .NET 6 will only support a single AppDomain, so this API will no longer be available in Xamarin.Android once .NET 6 is released.
 + [XA2001](xa2001.md): Source file '{filename}' could not be found.
 + [XA2002](xa2002.md): Can not resolve reference: \`{missing}\`, referenced by {assembly}. Perhaps it doesn't exist in the Mono for Android profile?
 + XA2006: Could not resolve reference to '{member}' (defined in assembly '{assembly}') with scope '{scope}'. When the scope is different from the defining assembly, it usually means that the type is forwarded.

Documentation/guides/messages/xa0036.md

@@ -8,7 +8,7 @@ ms.date: 06/17/2020
 ## Issue
 
 The `$(AndroidSupportedAbis)` MSBuild property is no longer supported
-in .NET 5 and higher.
+in .NET 6 and higher.
 
 ## Solution
 

Documentation/guides/messages/xa1023.md

@@ -12,7 +12,7 @@ warning XA1023: Using the DX DEX Compiler is deprecated. Please set the DEX comp
 ```
 
 ```
-error XA1023: Using the DX DEX Compiler is not supported in Xamarin.Android projects that target .NET 5 or higher. Please set the DEX compiler to 'd8' in the Visual Studio project property pages or edit the project file in a text editor and set the 'AndroidDexTool' MSBuild property to 'd8'.
+error XA1023: Using the DX DEX Compiler is not supported in Xamarin.Android projects that target .NET 6 or higher. Please set the DEX compiler to 'd8' in the Visual Studio project property pages or edit the project file in a text editor and set the 'AndroidDexTool' MSBuild property to 'd8'.
 ```
 
 ## Issue
@@ -21,7 +21,7 @@ Google has deprecated the DX DEX Compiler in favor of the [D8 DEX
 Compiler][d8]. On [February 1, 2021][dx], DX will no longer be a part
 of Android SDK or Android Studio.
 
-The DX DEX Compiler will not supported in .NET 5 or higher.
+The DX DEX Compiler will not supported in .NET 6 or higher.
 
 [d8]: https://developer.android.com/studio/command-line/d8
 [dx]: https://android-developers.googleblog.com/2020/02/the-path-to-dx-deprecation.html

Documentation/guides/messages/xa1024.md

@@ -8,15 +8,15 @@ ms.date: 07/08/2020
 ## Example messages
 
 ```
-warning XA1024: Ignoring configuration file 'Foo.dll.config'. .NET configuration files are not supported in Xamarin.Android projects that target .NET 5 or higher.
+warning XA1024: Ignoring configuration file 'Foo.dll.config'. .NET configuration files are not supported in Xamarin.Android projects that target .NET 6 or higher.
 ```
 
 ## Issue
 
 No support for [configuration files][config] such as `Foo.dll.config`
 or `Foo.exe.config` is available in Xamarin.Android projects targeting
-.NET 5 or higher. [`<dllmap>`][dllmap] configuration elements are not
-supported in .NET 5 at all, and other element types for compatibility
+.NET 6 or higher. [`<dllmap>`][dllmap] configuration elements are not
+supported in .NET 6 at all, and other element types for compatibility
 packages like [System.Configuration.ConfigurationManager][nuget] have
 never been supported in Xamarin.Android projects.
 

Documentation/guides/messages/xa1026.md

@@ -12,7 +12,7 @@ warning XA1026: Using AAPT is deprecated in favor of AAPT2. Please enable 'Use i
 ```
 
 ```
-error XA1026: Using AAPT is not supported in Xamarin.Android projects that target .NET 5 or higher. Please enable 'Use incremental Android packaging system (aapt2)' in the Visual Studio project property pages or edit the project file in a text editor and set the 'AndroidUseAapt2' MSBuild property to 'true'.
+error XA1026: Using AAPT is not supported in Xamarin.Android projects that target .NET 6 or higher. Please enable 'Use incremental Android packaging system (aapt2)' in the Visual Studio project property pages or edit the project file in a text editor and set the 'AndroidUseAapt2' MSBuild property to 'true'.
 ```
 
 ## Issue

Documentation/guides/messages/xa2000.md

@@ -8,7 +8,7 @@ ms.date: 1/13/2019
 ## Example messages
 
 ```
-Use of AppDomain.CreateDomain() detected in assembly: {assembly}. .NET 5 will only support a single AppDomain, so this API will no longer be available in Xamarin.Android once .NET 5 is released.
+Use of AppDomain.CreateDomain() detected in assembly: {assembly}. .NET 6 will only support a single AppDomain, so this API will no longer be available in Xamarin.Android once .NET 6 is released.
 ```
 
 ## Solution

build-tools/create-packs/Directory.Build.targets

@@ -37,9 +37,9 @@
   <Target Name="_GenerateFrameworkListFile" >
     <!-- Hardcode framework attributes -->
     <ItemGroup>
-      <FrameworkListRootAttributes Include="Name" Value=".NET 5.0 - Android" />
+      <FrameworkListRootAttributes Include="Name" Value=".NET 6.0 - Android" />
       <FrameworkListRootAttributes Include="TargetFrameworkIdentifier" Value=".NETCoreApp" />
-      <FrameworkListRootAttributes Include="TargetFrameworkVersion" Value="5.0" />
+      <FrameworkListRootAttributes Include="TargetFrameworkVersion" Value="6.0" />
       <FrameworkListRootAttributes Include="FrameworkName" Value="Microsoft.Android" />
     </ItemGroup>