AJAX :: How To Add Dynamic ModalPopupExtender Modal Popup To Page

i have created a class as follows which will create a dynamic popup 

public static void createModal() {
Button btnShow = new Button();
btnShow.ID = "btnCancel";
Panel p = new Panel();
p.ID = "ModalPanel";
p.Height = Unit.Percentage(300);
p.Width = Unit.Percentage(800);

[Code]......

And in my page my design is as follows

<asp:ScriptManager ID="script" runat="server"></asp:ScriptManager>
<asp:UpdatePanel ID="up" runat="server" UpdateMode="Conditional" ChildrenAsTriggers="true">
<%--<Triggers>
<asp:PostBackTrigger ControlID="btnShow" />
</Triggers>--%> <ContentTemplate>
<asp:Button ID="btnShow" runat="server" Text="Open" OnClick="btnShow_Click"></asp:Button>
</ContentTemplate>
</asp:UpdatePanel>

This is my code on button click to show the popup

protected void btnShow_Click(object sender, EventArgs e) {
common.createModal(btnShow);
}

If i didnot include the trigger on the page modal is not showing, but if I include the trigger modal popup is showing, can this be achieved with out registering the triggers.