I get "Unable to add reference" when I try to add my PCL as reference. The projects are in the same solution. The error message doesn't say anything more.
When I try to add the .dll via Browse... I get the an error telling me that I can not add a PCL targeted at .NET Framework to a project targeting .NETCore.
What's wrong?
The error is that your PCL is targeted at .NET Framework and not .NETCore. .NETCore does only contain a subset of .NET Framework.
To solve this, replace your PCL project with a Class Library (Portable for Universal Apps).