DLL framework errors

Hi fold,

I am build a WebAPI/MVC  application.  It works fine without configuring CORS. When I added the CORS dll, I am receiving this errors. I think it has to do with target framework vs version framework but I don't know how to resolve this.

could not load type 'system.runtime.compilerservices.scriptassemblyattribute' from assembly 'mscorlib, version=4.0.0.0,

Please help