title: Method not firing on textbox text change
body: <p>I have a textbox with a calander extender attached:</p>
  
  <pre><code>&lt;asp:TextBox ID="customDateTo" runat="server" AutoPostBack="true" OnSelectionChanged="customDateFrom_SelectionChanged"&gt;&lt;/asp:TextBox&gt;
  &lt;ajaxToolkit:CalendarExtender ID="toCalendarExtender" TargetControlID="customDateTo" runat="server"&gt;&lt;/ajaxToolkit:CalendarExtender&gt;
  </code></pre>
  
  <p>As you see I have <code>AutoPostBack="true"</code> and <code>OnSelectionChanged="customDateFrom_SelectionChanged</code> assigned for the textbox.</p>
  
  <p>However nothing is responding in my method:</p>
  
  <pre><code>protected void customDateFrom_SelectionChanged(object sender, EventArgs e)
  {
      System.Diagnostics.Debug.WriteLine("Do Something");
  }
  </code></pre>
  
  <p>When I change the text I do get a postback but nothing within the method is executing. Why is this happening and how do I fix it?</p>