Mmmk. YOu need to be clear on what you want.
If you want the contents of a .cs or .vb
file (or any server side code that may be included in a .aspx file) there is no way for you to get this code since every request you make to a particular URL will cause IIS to process the file.
If all you want is the resulting output of a given URL, as Peter said, you can use WebRequest to make a request to a given URL and then the Response stream that comes back you can place into a string variable eventually.
Read this if you want to know how to get a correct reply for your question:
Technical Editor for:
Professional Search Engine Optimization with ASP.NET
Professional IIS 7 and ASP.NET Integrated Programming