title: Setting DefaultButton to button.UniqueID throws exception
body: <p>The problem I'm trying to solve:</p>
  
  <p>I have several text boxes in an <code>asp:Panel</code>. When the user hits <code>Enter</code> from any of those boxes, I want the form to submit as if they've clicked <code>btnAddTag</code>. (When the cursor is not in those boxes, I have a different default submit button.)</p>
  
  <p>The aspx:</p>
  
  <pre><code>&lt;asp:Panel id="thePanel" runat="server"&gt;
      &lt;asp:Button ID="btnAddTag" Text="Add Tag" runat="server" /&gt;
  &lt;/asp:Panel&gt;
  </code></pre>
  
  <p>The vb:</p>
  
  <pre><code>tagPanel.DefaultButton = btnAddTag.UniqueID
  </code></pre>
  
  <p>The exception:</p>
  
  <blockquote>
    <p>The DefaultButton of 'tagPanel' must
    be the ID of a control of type
    IButtonControl.</p>
  </blockquote>
  
  <p>The value of <code>btnAddTag.UniqueID</code> is <code>ctl00$phMain$btnAddTag</code> (there's a master page, this section is called <code>phMain</code>).</p>
  
  <p>I've also tried <code>CType(tagPanel.FindControl("btnAddTag"), Button).UniqueID</code>.</p>