title: input hidden and updatePanel (a story of ASP.NET AJAX)
body: <p>How can update a input hidden inside an UpdatePanel on an AsyncPostBack?</p>
  
  <p>The user click a button outside the panel. The method associated with click event update the value of the input (it has runat="server" property).</p>
  
  <p>I can't update the value of this input.</p>
  
  <p>I need to store a value to use in the following postback. Maybe I can use session to store this value.</p>
  
  <p>Any advice?</p>
  
  <p>Thank you!</p>