Ajax Modal pop up extender error No Source Found

Question

Please some one help me..I am getting the Error "No source found for ajax modal pop up extender". I searched on net and i found that there are different solutions for this problem. I tried all of them but could not find my solution!!

I have added ajax control tool 4.0 kit to my project, my vs is 2010.

My page:

        <%@ Page Language="C#" AutoEventWireup="true" CodeFile="UserDetails.aspx.cs" Inherits="UserDetails" %>
        <%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="ajax" %>
    .
    .
    .
    .

  <form id="form1" runat="server">
  <ajax:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server">
   </ajax:ToolkitScriptManager>
   <div align="center">
    <h3 style="color: Olive" align="center" >
            User Details

   .
   .
   .
   .
     </table>

    <asp:LinkButton ID="lnk" Text="" runat="server"></asp:LinkButton>
    <ajax:ModalPopupExtender ID="ModalPopupExtender1" runat="server" TargetControlID="lnk" CancelControlID="btnClose" PopupControlID="pnlPop">
    </ajax:ModalPopupExtender>

   <asp:Panel ID="pnlPop" runat="server" Visible="false">
        <div>
            Display
        </div>
        <div>
            <table border="0" cellspacing="0" cellpadding="0">
                <tr
        .....
    <asp:Button ID="btnClose" runat="server" Text="Close" CssClass="button" />

in my code behind:

      protected void gdView_SelectedIndexChanged(object sender, EventArgs e)
{
    lbName.Text = gdView.SelectedRow.Cells[0].Text;
    ModalPopupExtender1.Show();
}

Answer 1

I found my mistake!! It is just panel visibility has been set to false!! It is not being found if i set visible to false!!!

Answer 2

 <asp:ScriptManager ID="ScriptManager1" runat="server" />

 <div align="center" style="z-index: 10000">
        <asp:Button ID="btnShowPopup" runat="server" Style="display: none" />
         <asp:Panel ID="pnlPop" runat="server" Style="display: none;>
        <div>
            Display
        </div>
        </asp:Panel>
        <ajax:ModalPopupExtender runat="server" ID="ModalPopupExtender1" TargetControlID="btnShowPopup"
            BackgroundCssClass="modalBackground" PopupControlID="pnlPop" />
    </div>

Code Behind:

protected void gdView_SelectedIndexChanged(object sender, EventArgs e)
{
    lbName.Text = gdView.SelectedRow.Cells[0].Text;
    ModalPopupExtender1.Show();
}