ModalPop

.aspx
 <asp:ImageButton ID="ThemaAdd_IB" CssClass="svaeButtonAlign"
            ImageUrl="~/Images/Common/bt_save.gif" runat="server"
            ValidationGroup="validatorCheck" onclick="ThemaAdd_IB_Click" />
        <asp:ModalPopupExtender ID="ThemaAdd_IB_ModalPopupExtender" runat="server"
            DynamicServicePath="" Enabled="False" TargetControlID="ThemaAdd_IB"
            PopupControlID="Modal_Panel" BackgroundCssClass="modalBackground"
            CancelControlID="ThemaList_LB" OkControlID="ThemaAdd_LB"
            onokscript="onOk()" oncancelscript="onCancel()">
        </asp:ModalPopupExtender>

.cs
protected void ThemaAdd_IB_Click(object sender, ImageClickEventArgs e)
        {
            Core.ThemaCategory tc = new Core.ThemaCategory();
            tc.themaCategoryAdd(ThemaCategoryName_TB.Text.Trim(), int.Parse(ThemaCategoryRepeat_TB.Text.Trim()));
           
            ThemaAdd_IB_ModalPopupExtender.Enabled = true;
            ThemaAdd_IB_ModalPopupExtender.Show();
            //ThemaAdd_IB_ModalPopupExtender.Hide();
        }