C#: What references and "usings" are required in order to access "ISldWorks"?

I am trying to run the C# sample in this video:

    http://www.youtube.com/watch?v=aoXJGKAwhbc

This is the relevant source code:

In the video, I cannot find the required references and usings, so I have been trying everything I can find. As you can see above the class "ISldWorks" is still not recognized,

TIA

SolidworksApi macros