This is a generic type, and one of those which no one can afford to be unaware of.
Before going to TWAIN and other advanced issues, I would advise you to learn the language and basics of .NET. As you don't even know generics, you cannot move much further. You need to learn all the language, not just simple fragments. Read this:
http://msdn.microsoft.com/en-us/library/aa479859.aspx[
^].
—SA