Is there any way but copying the .cs files?
Changing the .csproj file? But how?
There is a related question, but I'm not satisfied with the answer: link
Is there any way but copying the .cs files?
Changing the .csproj file? But how?
There is a related question, but I'm not satisfied with the answer: link
You may not be satisfied with the answer, but it's still the right one and this is still a dupe I'm afraid.
Honestly, it would take no more than an hour to refactor.
You need to manually edit the .proj file and remove the <ProjectTypeGuids> element.
You might also want to remove the other elements relating to IIS. Do a compare on this .proj file and one from a properly set up class library.