title: how to check whether excel file is of 2007 or 2010 office
body: <p>i am using following code to differentiate excel file of 2003 and 2007 office.</p>
  
  <pre><code>if (Extension == ".xls" || Extension == ".xlsx")
   {
   }
  </code></pre>
  
  <p>but now i also need to identify 2010 excel file. please suggest some solution.</p>