access a com object from .net?

i am trying to use the activedesktop class from the shell32.dll in my c# application. if i add shell32.dll to my reference list using visual studio, the activedesktop class does not show up. if i use tlbimp.exe, and ildasm.exe to view the resulting assembly, activedesktop is not in there. the documentation says activedesktop is in shell32.dll and a simple explorer string seach shows that activedesktop is in there. how do i reference activedesktop in my c# application? thanks.