I am also on MVC6 and have issues with Response.Headers even after adding "Microsoft.Net.Http.Server": "1.0.0-rc1-final". First it wants an instance of Response. Then if you create an instance, it needs a constructor with arguments but doesn't provide any hints and I couldn't find any one google.
Also, I also get an error that 'File' cannot be used as a method when I try to return the file:
return File(System.IO.File.ReadAllBytes(@"D:\MyFiles\Resume.doc"), "application/ms-word", "Resume.doc");
Any suggestions?