Unresolved external symbol on static class members

Question

Very simply put:

I have a class that consists mostly of static public members, so I can group similar functions together that still have to be called from other clas

Answer 1

In my case, I was using wrong linking.
It was managed c++ (cli) but with native exporting. I have added to linker -> input -> assembly link resource the dll of the library from which the function is exported. But native c++ linking requires .lib file to "see" implementations in cpp correctly, so for me helped to add the .lib file to linker -> input -> additional dependencies.
[Usually managed code does not use dll export and import, it uses references, but that was unique situation.]