VS gives me errors when I try to do it. Yet, it displays such projects as available to reference. Is it possible to add winRT project reference to the classic class library project somehow?
If not, how to bridge both worlds, so common logic can be stored in one place?
The short answer is yes. The long answer is that it’s not supported and comes with some caveats that you need to understand.
See my answer here:
Using Custom Windows Runtime Components in Non-Metro Applications