title: Button inside Update Panel is not triggered, in asp.net
body: <pre><code>&lt;asp:ModalPopupExtender ID="MPE_EditGroup" runat="server" TargetControlID="btnShowPopup" PopupControlID="pnlpopup" CancelControlID="btnCancel" /&gt;
  &lt;asp:ToolkitScriptManager ID="ScriptManager1" runat="server" /&gt;
  &lt;asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional" ChildrenAsTriggers="false"&gt;
      &lt;ContentTemplate&gt;
          &lt;asp:Panel ID="pnlpopup" runat="server"&gt;
              &lt;asp:ListBox ID="lst_allmembers" DataValueField="FirstName" runat="server" /&gt;                       
              &lt;asp:Button ID="btn_Add" runat="server" Text="Add" OnClick="btn_Add_Click" /&gt;&lt;asp:ListBox ID="lst_grpmembers" runat="server" /&gt;
              &lt;asp:Button ID="btn_remove" runat="server" Text="Remove" /&gt;
              &lt;asp:Button ID="btnUpdate" CommandName="Update" runat="server" Text="Update" OnClick="btnUpdate_Click" /&gt;
              &lt;asp:Button ID="btnCancel" runat="server" Text="Cancel" /&gt;&lt;/asp:Panel&gt;
      &lt;/ContentTemplate&gt;
  &lt;/asp:UpdatePanel&gt;
  </code></pre>
  
  <p>The add button has a event OnClick="btn_Add_Click" </p>
  
  <pre><code>  protected void btn_Add_Click(object sender, EventArgs e)
    {
          lst_grpmembers.Items.Add(lst_allmembers.SelectedItem.Text);
               }
  </code></pre>
  
  <p>The event is not triggered and when I click the add button nothing happens. And the Update Button was working fine before I added the update panel now only the cancel button closes the popup no other button works inside the pop up
  How to trigger the event.</p>