title: IPostBackEventHandler RaisePostBackEvent not triggered on asynchronous postback
body: <p>I have designed a custom user control, basically a button, that implements the <code>IPostBackEventHandler</code> interface, and obviously defines the <code>RaisePostBackEvent(string eventArgument)</code> method, where I do some processing, basically I trigger other events. </p>
  
  <p>By default, when clicked my control will execute <code>__doPostBack</code> its client id for a full page refresh, and of course RaisePostBackEvent is triggered.</p>
  
  <p>However, I want to be able the use the control to refresh an update panel, so from client side I use the <code>__doPostBack</code> method with the ID of the update panel and an additional argument. </p>
  
  <p>The problem is that <code>RaisePostBackEvent</code> is not triggered. I know i could look in <code>Page.Request.Params["__EVENTARGUMENT"]</code> and do whatever I need, but I would really like something as simple and elegant as <code>IPostBackEventHandler</code> so as to have all the logic in my control. </p>
  
  <p>Long story short, how can I trigger <code>RaisePostBackEvent</code> in case I have an asynchronous postback? Or is there another interface that with similar functionality?</p>