Show Progress Bar when uploading files using AJAX UpdateProgress

hi guys.. i having difficulties to show progress bar when uploading files using AJAX UpdateProgress.

my progress bar is disappear even i have paste the following javascript. pls advise. TQ

<script type="text/javascript">
window.onsubmit = function () {
    if (Page_IsValid) {
        var updateProgress = $find("<%= UpdateProgress1.ClientID %>");
        window.setTimeout(function () {
            updateProgress.set_visible(true);
        }, 100);
    }
}</script>

<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager><asp:UpdateProgress ID="UpdateProgress1" runat="server" AssociatedUpdatePanelID="UpdatePanel1"><ProgressTemplate><div class="modal"><div class="center"><img alt="" src="loader.gif" /></div></div></ProgressTemplate></asp:UpdateProgress><asp:UpdatePanel ID="UpdatePanel1" runat="server"><ContentTemplate><div style="margin: 20px"><asp:FileUpload ID="FileUpload1" runat="server" /><br /><asp:Button ID="btnUpload" Text="Submit" runat="server" /></div></ContentTemplate><Triggers><asp:PostBackTrigger ControlID="btnUpload" /></Triggers></asp:UpdatePanel>