强制显示UpdateProgress

<asp:ScriptManager ID="ScriptManager1" runat="server" ScriptMode="Debug">
</asp:ScriptManager>

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
        <%= DateTime.Now %><br />
        <asp:Button ID="Button1" runat="server" Text="Button1" OnClick="Button_OnClick" />
    </ContentTemplate>
    <Triggers>
        <asp:AsyncPostBackTrigger ControlID="Button2" />
    </Triggers>
</asp:UpdatePanel>

<asp:UpdateProgress ID="UpdateProgress1" runat="server" DisplayAfter="0" DynamicLayout="false"
    AssociatedUpdatePanelID="UpdatePanel1">
    <ProgressTemplate>
        <span style="color:Red">Loading</span>
    </ProgressTemplate>
</asp:UpdateProgress>

<hr />
<asp:Button ID="Button2" runat="server" Text="Button2" OnClick="Button_OnClick" />


<script language="javascript" type="text/javascript">
    Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(
        function(sender, e)
        {
            if (e.get_postBackElement().id != "<%= this.Button2.ClientID %>")
            {
                return;
            }
            
            var updateProgress = $get("<%= this.UpdateProgress1.ClientID %>");
            var dynamicLayout = <%= this.UpdateProgress1.DynamicLayout.ToString().ToLower() %>;
            
            if (dynamicLayout)
            {
                updateProgress.style.display = "block";
            }
            else
            {
                updateProgress.style.visibility = "visible";
            }
        });
</script>

//后台代码

    protected void Button_OnClick(object sender, EventArgs e)
    {
        Thread.Sleep(2000);
    }