modal popup not showing from code behind - asp.net

Question

<asp:UpdatePanel ID="updtpnlacademic" runat="server">
<ContentTemplate>
<td>
<asp:GridView ID="gdvwAcademic1" runat="server" OnRowCommand="gdvwAcademic1_RowCommand" OnRowDeleting="gdvwAcademic1_RowDeleting" CellPadding="4" ForeColor="#333333" GridLines="None" Width="100%" AllowSorting="True" AutoGenerateColumns="False" HorizontalAlign="Center">
<Columns>
....Other column fields
<asp:TemplateField HeaderText="Delete" ItemStyle-HorizontalAlign="Center" ShowHeader="false">
<ItemTemplate>
<asp:ImageButton ID="imgbtnacademicdelete" CommandName="Delete" OnClick="imgbtnacademicdelete_Click" CommandArgument='<%# ((GridViewRow)Container).RowIndex %>' ToolTip="Delete" runat="server" ImageAlign="Top" ImageUrl="~/Images/delete.png" Width="30" Height="25"/>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
<asp:Button ID="btndummy" runat="server" Visible="false" />
<cc1:ModalPopupExtender ID="mpacademic" runat="server" TargetControlID="btndummy" PopupControlID="Panel2" CancelControlID="btnacademicClose" BackgroundCssClass="modalBackground">
</cc1:ModalPopupExtender>
<asp:Panel ID="Panel2" runat="server" CssClass="modalPopup" HorizontalAlign="Center" style = "display:none">
<span style="color:white; font-family:'Bookman Old Style'; font-weight:bold;">Really Want To Delete This Record...!</span><br /><br /><br /><br />
<asp:Button ID="btnconfirmacademicdelete" OnClick="btnconfirmacademicdelete_Click" CssClass="BStyle" Font-Bold="true" runat="server" Text="Yes" />
<asp:Button ID="btnacademicClose" Font-Bold="true" runat="server" CssClass="BStyle" Text="Cancel" />
</asp:Panel>
</td>
</ContentTemplate>
</asp:UpdatePanel>
And following code as in the code behind ....
protected void gdvwAcademic1_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
mpacademic.Show();
//System.Windows.Forms.MessageBox.Show("RowDeleting clicked after this modal popup should be displayed.....!");
}
It only show messagebox on event if uncomment messagebox but not showing modal popup

Answer 1

<cc1:ModalPopupExtender ID="mpacademic" runat="server" TargetControlID="btndummy" PopupControlID="Panel2" CancelControlID="btnacademicClose" BackgroundCssClass="modalBackground">
</cc1:ModalPopupExtender>
The TargetControlID property is set to btndummy and
<asp:Button ID="btndummy" runat="server" Visible="false" />
btndummy is not rendering since Visible property is set to false.
Try to replace
<asp:Button ID="btndummy" runat="server" Visible="false" />
With
<asp:Button ID="btndummy" runat="server" style="display:none" />