title: Unable to find control in Update Panel for trigger
body: <p>In our application of asp.net with c#, we are using Ajax with update panel control.
  In panel, we have put export to excel button inside tab panel.</p>
  
  <p>We have also put triggers after ending of content template. Please find below code for your reference.</p>
  
  <pre><code>&lt;asp:UpdatePanel ID="UpdatePanelPage" runat="server" UpdateMode="Conditional"&gt;
      &lt;ContentTemplate&gt;
  
          &lt;table id="tblMain" runat="server" cellpadding="0" cellspacing="0"    width="100%"&gt;
               &lt;tr&gt;
                   &lt;td&gt;
                       &lt;asp:TabContainer ID="TabContainer1" runat="server" Width="100%"&gt;
                           &lt;asp:TabPanel ID="tabCompanyName" runat="server"&gt;
            &lt;asp:Button ID="btnStateExportToExcel" runat="server" Text="Export To Excel"    CssClass="button" OnClick="btnStateExportToExcel_Click" /&gt;
     &lt;/asp:TabPanel&gt;
  &lt;/asp:TabContainer&gt;
                    &lt;/td&gt;
              &lt;/tr&gt;
          &lt;/table&gt;
      &lt;/ContentTemplate&gt;
     &lt;Triggers&gt;
            &lt;asp:PostBackTrigger ControlID="btnStateExportToExcel" /&gt;
       &lt;/Triggers&gt;
              &lt;/asp:UpdatePanel&gt;
  </code></pre>
  
  <p>Now when we run the page following error would be display.
  “A control with ID 'btnStateExportToExcel' could not be found for the trigger in UpdatePanel 'UpdatePanelPage'.“
  Any idea/suggestion would be highly appreciable.</p>
  
  <p>*As per search results of Google, the button resides in tab panel due to which page was not able to find this control.  </p>