im using that code.

asp:LinkButton ID="lbn_job_det" runat="server" Text="View Job Details" Font-Names="Calibri"></asp:LinkButton>

     <ajaxtoolkit:modalpopupextender id="ModalPopupExtender" runat="server" backgroundcssclass="modalBackground" cancelcontrolid="CancelButton" dropshadow="true" okcontrolid="OkButton" popupcontrolid="Panel1" popupdraghandlecontrolid="Panel3" targetcontrolid="lbn_job_det"></ajaxtoolkit:modalpopupextender>

<asp:Panel ID="Panel1" runat="server" CssClass="modalPopup"  Style="display: none" Width="380px" Height="96px">

           <div>

<p style="text-align: center">

                   <table width="100%">

                 </table>

                   <br /><br />

                 <asp:Button ID="OkButton" runat="server" Text="OK" onclick="OkButton_Click" />

                   <asp:Button ID="CancelButton" runat="server" Text="Cancel" />

              </p>

          </div>

       </asp:Panel>

that  code working fine but button event not fire

protected void OkButton_Click(object sender, EventArgs e)

    {  }