title: checking if rss feed has updated
body: <p>I am writing an app for WP7 and would like to set up notifications for the client using the background services mango will be offering,</p>
  
  <p>I was hoping to check whether an XML file or any file on the Web has updated or changed in any way, then alert the user using a push notification if it did.</p>
  
  <p>I was thinking of checking the file's hash but I am unsure if that is even necessary and if there's another way of doing just that.</p>
  
  <p>Is there anything you guys would advise me to do? I have my WCF Service keeping track of unique hardware IDs, so recording the client's last hash would be an idea and when this hash changes execute an operation on my WCF service that pushes a notification to the client.</p>
  
  <p>I am looking for methods and information on how to go about dynamically notifying the clients.</p>