There are multiple ways to realize passing data between different classes.
One way is to pass it with a
System.File.Open (MSDN) already gives back a
FileStream. With streams you need to be careful with the handling of opening, closing, reading etc (see using).
Another way is by simply passing the path of the file as a string and open it elsewhere. But as you are trying to use a
HttpPostedFile-object, I guess you're working on a project running on 2 different machines.
You should read into streaming data, and with streaming it's irrelevant if you got the data from a file, a request or even another stream.
Edit: It seems your main first problem here was that the class
HttpPostedFile was in a assembly you didnt referenced before. You can get tips for situations like these by pressing
.. VS suggests you things like creating a class for unknown objects or, if it's a common known object, adding references.