*csis in the spec.
I reported this here in Microsoft Connect Feedback but Microsoft insist that it is by design. Weird!
Anyway, make sure that you add
*.aspx.csand other variants (eg
*.asmx.cs) to your file spec, separated by semi-colons. I also add
Actually, I've just noticed that the standard file spec has
*cs. If you change this to
*.cswith a period then it also works.