title: Adding c# code to existing .net core project with Roslyn
body: <p>Is it possible to load an existing .NET core project with Roslyn API, add a c# class and save it so the file is actually created on disk and added to the project.
  I tried to do it with MSBuildWorkspace and AddDocument and TryApplyChanges method - I can load the solution and project  but the file is not created (and I don't get any exception or error). </p>
  
  <p>Where can I find a working example that shows how to use Roslyn to accomplish something like that</p>