How to dynamically add items to list box inside Modal Popup in asp.net c#

Question

I have a Listbox which I add items to it in the OnClick event. I have this Listbox inside a panel( Pnl_Pdfviewers ) and table .

This panel is the pop up panel which is make it visible in the onclick event

  Onclickevent
   {
       //Call method to fill list box
       ModalPopupExtender2.Show();
   }


    // Fill list box
    reader = server.ExecuteReader(CommandType.Text, usernameQuery, paramete);
    while (reader.Read())
    {
        lst_PdfViewers.Items.Add(reader["Name"].ToString());
    }
    reader.Close();

everything is fine, but the listbox is always empty. I read the value from the table and add that to the listbox . Why is the listbox empty always?

<asp:ModalPopupExtender ID="ModalPopupExtender2" BackgroundCssClass="modalBackground"                 TargetControlID="btnShowPopup2"  CancelControlID="btn_PdfCancel"  PopupControlID="Pnl_Pdfviewers" runat="server"> </asp:ModalPopupExtender>
  <asp:Panel ID="Pnl_Pdfviewers" runat="server" BackColor="White" Height="250px" Width="350px" Style="display: none">
     <table>
        <tr>
          <td align="center">
             <asp:ListBox ID="lst_PdfViewers"   runat="server" ></asp:ListBox>
           </td>
         </tr>
     </table> 
  </asp:Panel>

UPDATE:

 DataSet ds = new DataSet();
            ds = server.ExecuteQuery(CommandType.Text, usernameQuery, paramete);
           lst_PdfViewers.DataSource = ds;
           lst_PdfViewers.DataBind();

Databinding is done successfully but it is not displaying inside the modal pop up extender

Answer 1

I ll suggest wrapping your Listbox with an UpdatePanel and calling myUpdatePanel.Update(); after

lst_PdfViewers.DataBind();

It works for us in similar cases. Hope it helps.