title: Find extension of file from URL
body: <p>I want to find what is the extension of file in current URL.
  I have used<br>
  <code>http://tol.imagingtech.com/eIL/cgi-bin/eIL.pl?ACTION=get_trans_doc&amp;DOC=ALL&amp;CAB_NAME=TOL_AP_2012&amp;WHSE=18&amp;PAYEE=23003655&amp;INV=01235770</code></p>
  
  <p>The extension of this file is (.pdf) how can i get this. Sometimes it will be (.doc,.txt,.jpeg) so i want the exact one.</p>
  
  <p>Following is the code which i used to retrieve file extension</p>
  
  <p><code>var extFile = Document.DocumentFilePath.Split('.');<br>
    return "Backup document." + extFile[extFile.Length-1].Trim().ToLower();</code></p>
  
  <p>It works fine for normal local path but it fails to retrieve extension which DocumentFilePath is url.</p>