This issue is related to dotnet/aspnetcore#60337, in which we enrich the webapiaot template with OpenAPI by default, which can be disabled with --no-openapi. In order to write endpoints with correct OpenAPI metadata, TypedResults and Results<T1,T2> are used, which are part of the Microsoft.AspNetCore.Http.HttpResults namespace.

The build of the mentioned PR failed because the usings for the mentioned types were not available. While researching this, I found out that this is because ImplicitUsings for ASP.NET Core projects doesn't add these types.

There are 2 options:

• Require every (new) project to add the HttpResults namespace with an explicit using
  • And to every file when endpoints are later on separated by files and TypedResults are used.
• Add Microsoft.AspNetCore.Http.HttpResults to the list of usings that should be globally added when ImplicitUsings is enabled, which is what this PR does. This prevents a bit of "using pollution", and is therefore (in my opinion) the preferred approach