title: The ControlID property must be set on the trigger in UpdatePanel 'UpdatePanel1'
body: <p>I have this code apsx:</p>
  
  <pre><code>&lt;asp:UpdatePanel runat="server" ID="UpdatePanel1" UpdateMode="Conditional" ChildrenAsTriggers="False"&gt;
      &lt;ContentTemplate&gt;
      &lt;asp:Button ID="btnUpdateTable" runat="server" Text="Actualizar" Visible="False" /&gt;
      &lt;asp:Button ID="btnGraph" runat="server" Text="Gráfico" Visible="False" PostBackUrl="ShowGraph.aspx" /&gt;
      &lt;asp:Button ID="btnExcel" runat="server" Text="Excel" Visible="False" /&gt;
      &lt;asp:Timer ID="Timer1" runat="server" Interval="5000"/&gt;
  
      &lt;table cellspacing="0" cellpadding="0" border="0"&gt;
          &lt;tr&gt;&lt;td&gt;
              &lt;div style="width: 100%"&gt;
  
                      &lt;asp:GridView ID="GridView1" runat="server" DataSourceID="SqlDataSource1" BorderColor="Silver"
                  BorderStyle="Solid" BorderWidth="1px" CellPadding="5" CellSpacing="1" CssClass="ttc"
                  ForeColor="Silver" HorizontalAlign="Left" AllowPaging="True" PageIndex="1"&gt;
                  &lt;PagerSettings LastPageImageUrl="~/Images/arrow_end.gif" PreviousPageImageUrl="~/Images/arrow_left.gif" FirstPageImageUrl="~/Images/arrow_beg.gif" Position="Top" NextPageImageUrl="~/Images/arrow_right.gif" Mode="NextPreviousFirstLast"&gt;&lt;/PagerSettings&gt;
                  &lt;RowStyle CssClass="ttc"&gt;&lt;/RowStyle&gt;
                  &lt;SelectedRowStyle CssClass="ttcs"&gt;&lt;/SelectedRowStyle&gt;
                  &lt;PagerStyle CssClass="ttc"&gt;&lt;/PagerStyle&gt;
                  &lt;HeaderStyle CssClass="thc"&gt;&lt;/HeaderStyle&gt;
                      &lt;/asp:GridView&gt; 
          &lt;/div&gt;
          &lt;/td&gt;&lt;/tr&gt;
          &lt;tr&gt;&lt;td&gt;
              &lt;asp:Panel ID="pnlLabelValues" runat="server"&gt;
          &lt;/asp:Panel&gt;
          &lt;/td&gt;&lt;/tr&gt;
      &lt;/table&gt;
      &lt;/ContentTemplate&gt;
    &lt;Triggers&gt;
      &lt;asp:PostBackTrigger ControlID="btnExcel" /&gt;
      &lt;/Triggers&gt;
  &lt;/asp:UpdatePanel&gt;
  </code></pre>
  
  <p>and I got the following message when I try to go on web site;</p>
  
  <blockquote>
    <p><em>The ControlID property must be set on the trigger in UpdatePanel 'UpdatePanel1'.
    Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.</em> </p>
    
    <p><em>Exception Details: System.InvalidOperationException: The ControlID property must be set on the trigger in UpdatePanel 'UpdatePanel1'.</em></p>
    
    <p><em>An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.</em></p>
  </blockquote>
  
  <p>and I can't find the solution!</p>
  
  <p>Can any one help me what I'm doing wrong?</p>