Preprocesser: with unknown number of 'include' files

I usually like to write a preprocesser in a new language inorder to learn the language.  That language is C#.  I have to deal with "include" file in the program. How do I express an arbitrary number of names for the instantiation of the 'include' files?  I thought about trying to 'type' an array as a StreamReader.  That way I could deal with the problem a LIFO stack.  My gut feeling is that that is not an appropriate way of doing it.