title: ASP.NET Repeater inside UpdatePanel, need to create PostBackTrigger
body: <p>I have an UpdatePanel which has a Repeater inside it, and inside of the Repeater is a Button that I want to be a PostBackTrigger for the UpdatePanel (not an AsyncPostBackTrigger).</p>
  
  <p>I have tried to create a trigger in the code behind in the Repeater's ItemDataBound event (using code below) but nothing I tried worked.</p>
  
  <pre><code>PostBackTrigger trigger = new PostBackTrigger();
  //failed
  //trigger.ControlID = "btnCourseAttachmentUpdateSubmit";
  //failed
  //trigger.ControlID = ((Button)e.Item.FindControl("btnCourseAttachmentUpdateSubmit")).ID;
  //failed
  //trigger.ControlID = ((Button)e.Item.FindControl("btnCourseAttachmentUpdateSubmit")).ClientID;
  //failed
  //trigger.ControlID = ((Button)e.Item.FindControl("btnCourseAttachmentUpdateSubmit")).UniqueID;
  panAttachments.Triggers.Add(trigger);
  </code></pre>
  
  <p>I know there is a technique to resolve this by using a hidden button but before I did that I wondered if there was a way of doing this similar to what I was trying in the code above?</p>