cannot add a reference .NET

Question

I have a DLL which I would like to add as a reference to my project, but everytime I try to do it a dialog pops up telling me:

The reference could not be

Answer 1

Some DLL's cant be added as a reference, but however, they can still be used by C# with the famous [DllImport( params go here...)]

You might also have to inspect the dll in order to get the address of the functions you want to use . This can be achieved by using GetProcAddress