title: Ext.net PageProxy: what is it and how does it work?
body: <p>I found that PageProxy can be used to get data from page, but I don't understand what does it mean exaclty and what's the difference with HttpProxy.
  In particular:</p>
  
  <ul>
  <li>who/when starts the request?</li>
  <li>how does the request interact with the page life cycle?</li>
  <li>where does the data come from? There is no url property on PageProxy.
  Thank you.</li>
  </ul>