No, I’m not. The dll compiles fine, the class I’m trying to use is visible in the output and public, and the reference is pointing to the right file. The IDE recognises it, and will even navigate to the definition, but it won’t compile.
Are you missing a reference?
No. The problem may be that the target framework of the dll is .NET Framework 4 and the the target framework of the exe is .NET Framework 4 Client Profile. Client Profile is the default target framework for Windows Services and Console Applications. Change it to .NET Framework 4 and all should be well.