title: How do I use UpdatePanel Trigger with a control outside of panel
body: <p>I have an issue where I need to trigger 2 update panels to update when the user clicks a button which is OUTSIDE of both of these panels</p>
  
  <pre><code>&lt;asp:UpdatePanel runat="server" ID="pnlDropDowns" UpdateMode="Conditional"&gt;
    &lt;Triggers&gt;
      &lt;asp:AsyncPostBackTrigger ControlID="btnUseMeter" Event="Click"/&gt;
    &lt;/Triggers&gt;
  &lt;ContentTemplate&gt;
  
  
  &lt;asp:UpdatePanel runat="server" ID="pnlChart" UpdateMode="Conditional"&gt;
    &lt;Triggers&gt;
      &lt;asp:AsyncPostBackTrigger ControlID="btnUseMeter"  Event="Click"/&gt;
    &lt;/Triggers&gt;
  &lt;ContentTemplate&gt;
  
  &lt;asp:Button ID="btnUseMeter" runat="server" Text="View Meter Data" Enabled="True"   OnClientClick="lowerFlag();" /&gt;                                             
  </code></pre>
  
  <p>I get the error </p>
  
  <p>A control with ID 'btnUseMeter' could not be found for the trigger in UpdatePanel 'pnlDropdowns'. </p>
  
  <p>Is there a way round this?  Is it possible to use a hidden field?  If so what would the event be?  I could possibly set the value of a hidden field to say when I want the panels to update?</p>
  
  <p>I have a considerable amount of HTML on this page so restructuring the page into a single panel is not an option, nor is moving the button to be inside either of the panels</p>
  
  <p>I am using C# .NET 4.5</p>
  
  <p>Cheers</p>
  
  <p>Paul            </p>