title: Can a TargetControlID of a PopUp use the Button of a GridView?
body: <p>I have a <code>Button</code> with <code>id=btnSend</code> that named "Send" in <code>GridView</code>. </p>
  
  <p>I have a <code>ModalPopUpExtender id="SendPopUp"</code> and <code>TargetControlID="btnSend"</code></p>
  
  <p>and</p>
  
  <pre><code>&lt;asp:Panel id="SendPanel"&gt;
  </code></pre>
  
  <p>I get the error as </p>
  
  <blockquote>
    <p>System.InvalidOperationException: The TargetControlID of '
    SendPopUp'is not valid. A control with ID 'btnSend' could not be
    found.</p>
  </blockquote>
  
  <p>How do I make it work?</p>