Ambiguous references with the exact same namespace

Question

The RC class is not linked to a database, it is a simple class. The class is at only one place and is not partial. The Aérochem.Domain dll project compiles just

Answer 1

I had this problem in a .NET standard project (I call it the host project). The namespace causing the problem was in another referenced project (which was also a .NET standard project) in the same solution.

I did everything: clean, delete resharper cache, close soln, delete .suo, delete binaries. Nothing seemed to work.

Then I converted the host project to .NET framework and then the problem disappeared.