One of the things that appeared to be lacking in ASP.NET 2.0 and above (or so I thought) is a utility library to parse and extract paths and get the file name from a Url. Here are some examples of the url parsing code that I and others have done without knowledge of this library: http://www.thejackol.com/2007/04/10/get-file-name-from-url-cnet/
One class that does just this (and which most developers don't know about) is System.Web.VirtualPathUtility(). Everyone knows it's brother utility library System.Web.HttpUtility but VirtualPathUtility should be an essential part of any ASP.NET developer's toolkit. See http://msdn.microsoft.com/en-us/library/system.web.virtualpathutility.aspx for more information.