I have wondered for a long time how to access a Types XML comment data at run-time. I know that comments are normally thrown away in languages, but I figured that .NET must keep the XML comments around somewhere, how else could they display the information through intellisense for user created DLLs.
Well, according to this article that I just found, the XML comments are thrown away like all other comments at compile time.
It seems that intellisense attempts to load a separate .XML file to display the comments.

The article provides some interesting insight into how it works, I suggest that you look into it if that sort of thing interest you.