title: Save data before leave the page in ASP.NET
body: <p>I have asp.net page. 
  I don't have button "Save" on it (not my requirement).</p>
  
  <p>I need to save page data before I leave this page.</p>
  
  <p>I've tried to do it with events like <code>Page_Unload</code> but it doen't work...
  Cause <code>Save</code> method uses data from elements on page like <code>txtBox1.Text</code> I can't use <code>.ashx</code> handler to make some <code>ajax</code> save (Or I don't know how to use page elements in handler as they are <code>protected</code>). </p>
  
  <p>So is there any solution except serealizing form and pass it to handler?</p>