Ensure <Using /> declarations from in-box SDKs are conditioned on C#

[DamianEdwards]

The new <Using /> item type is explicitly intended to only be used in C# projects. The code generation targets and core global usings items are already conditioned on C# but we should ensure that the higher-level SDKs (e.g. Web, Worker, WindowsDesktop, etc.) also condition any using item types they bring in by C# too.

• Current Web props: https://github.com/dotnet/sdk/blob/main/src/WebSdk/Web/Sdk/Sdk.props#L61
• Current Worker props: https://github.com/dotnet/sdk/blob/main/src/WebSdk/Worker/Targets/Microsoft.NET.Sdk.Worker.props#L41
• Current BlazorWasm props: https://github.com/dotnet/sdk/blob/main/src/BlazorWasmSdk/Sdk/Sdk.props#L23
• Current WinForms props: https://github.com/dotnet/winforms/blob/main/pkg/Microsoft.Private.Winforms/sdk/dotnet-wpf/Microsoft.NET.Sdk.WindowsDesktop.WindowsForms.props#L15
• Current WPF props: https://github.com/dotnet/wpf/blob/main/packaging/Microsoft.NET.Sdk.WindowsDesktop/targets/Microsoft.NET.Sdk.WindowsDesktop.WPF.props#L5

[mhutch]

To be absolutely explicit, is this the behavior (and pattern) we expect targets in all the workload SDKs to follow?

<ItemGroup Condition="'$(Language)' == 'C#' And ('$(ImplicitUsings)' == 'true' or '$(ImplicitUsings)' == 'enable')">

Should we have the SDK targets compute a property to centralize this logic? For example, if the SDK targets did this:

<PropertyGroup>
  <_CSharpImplicitUsings
      Condition="'$(Language)' == 'C#' And ('$(ImplicitUsings)' == 'true' or '$(ImplicitUsings)' =='enable')"
  >
  true
  </_CSharpImplicitUsings>
</PropertyGroup>

Then workload targets could do this:

<ItemGroup Condition="'$(_CSharpImplicitUsings)' == 'true')">

[DamianEdwards]

@mhutch that satisfies the desired specificity I think, so sure 😃

[RussKie]

WPF props: https://github.com/dotnet/wpf/blob/main/packaging/Microsoft.NET.Sdk.WindowsDesktop/targets/Microsoft.NET.Sdk.WindowsDesktop.WPF.props