A search for empty “Reference.cs” – Google Search seems to indicate this happens with referenced types that – despite turning off that option – from the Visual Studio 2017 IDE sometimes results in an empty Reference.cs.
My solution: import in an empty project, then move the reference to the existing project and add it.
[WayBack] c# – Sometimes adding a WCF Service Reference generates an empty reference.cs – Stack Overflow
–jeroen