netexptestdll.dll implements base classes that can be tested. This file is available at <public user documents>\Silk Performer 20.0\SampleApps\DOTNET\netexptestdll\bin\debug\netexptestdll.dll.
You can instantiate one of the loaded objects via the context menu on the class or by invoking a constructor. Following that, store the created object in a variable and call methods on the created object.