ASP.NET AJAX Discussion and Suggestions

Re: Start callback immediately after page loaded

Jin-Yu Yin - MSFT — Tue, 24 Jul 2007 06:14:29 GMT

If the contents of the panel are very large,you can delay by several seconds to load the content.

You don't need to load it when the whole page load.when the whole page is loading,set the panel unvisible.

Then load the content of the panel.

Code as follow:

<%@ Page Language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<script runat="server">
    protected void Button1_Click(object sender, EventArgs e)
    {
        System.Threading.Thread.Sleep(3000);
        TextBox1.Text = DateTime.Now.ToString();
    }
</script>

<script type="text/javascript">
function delayLoad()
{
document.getElementById("<%= Button1.ClientID %>").click();
document.getElementById("<%= UpdateProgress1.ClientID %>").style.display = "block";
}
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" runat="server">
    <title>Untitled Page</title>
</head>
<body onload="setTimeout('delayLoad()',3000)">
    <form id="form1" runat="server">
    <div>
        <asp:ScriptManager ID="ScriptManager1" runat="server">
        </asp:ScriptManager>
        <asp:UpdatePanel ID="UpdatePanel1" runat="server" UpdateMode="Conditional">
            <ContentTemplate>
                <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
                <div visible="true"><asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" /></div>
            </ContentTemplate>
        </asp:UpdatePanel>
        <asp:UpdateProgress ID="UpdateProgress1" runat="server" AssociatedUpdatePanelID="UpdatePanel1">
            <ProgressTemplate>
                Waiting..............
            </ProgressTemplate>
        </asp:UpdateProgress>
    </div>
    </form>
</body>
</html>

More informatin,see:Delaying Content Load using Timer and UpdatePanel AND Controlling visibility of contents of collapsiblepanel

Thanks

Re: Start callback immediately after page loaded

miksh — Thu, 19 Jul 2007 15:24:04 GMT

gt1329a:
If it feels better to abstract how you inject them, you could use ClientScript.GetPostBackEventReference(UpdatePanel1, "") to generate the actual call.

This looks more resanable, thanks. So far, I added a hidden button inside an UpdatePanel and make a javasript's click on it to trigger the update. But I like your approach more.

Re: Start callback immediately after page loaded

gt1329a — Thu, 19 Jul 2007 15:14:23 GMT

They really aren't anything to worry about, in my experience. If you've ever used a GridView, DataGrid, LinkButton, or half a dozen other common controls, you're already relying on the __doPostBack() mechanism.

If it feels better to abstract how you inject them, you could use ClientScript.GetPostBackEventReference(UpdatePanel1, "") to generate the actual call.

Re: Start callback immediately after page loaded

miksh — Thu, 19 Jul 2007 11:24:30 GMT

Usually I try to avoid any explicit __doPostBack(...) calls.

Re: Start callback immediately after page loaded

Steve Marx — Thu, 19 Jul 2007 02:53:15 GMT

Here are a couple more ideas I blogged a while ago: http://smarx.com/posts/delayed-load-with-an-updatepanel.aspx.

Re: Start callback immediately after page loaded

gt1329a — Thu, 19 Jul 2007 01:46:25 GMT

Which part are you uncomfortable with?

Re: Start callback immediately after page loaded

miksh — Thu, 19 Jul 2007 00:58:13 GMT

Thanks, I'll try but IMHO this hack might be not compatible with the next ajax versions.

I forgot to mention that my UpdatePanel is updated by a timer. Is there any way to fire the timer's OnTick event immediately?
Any other ideas to trigger the UpdatePanel on client-side?

Re: Start callback immediately after page loaded

gt1329a — Thu, 19 Jul 2007 00:18:12 GMT

You could use the OnLoad event of the UpdatePanel to render the panel's contents, and IsPostBack to not render that content on the initial page load. Then, in your client script, call __doPostBack("UpdatePanel", '') from pageLoaded() to trigger that UpdatePanel_Load code.

Start callback immediately after page loaded

miksh — Wed, 18 Jul 2007 20:47:37 GMT

I have a UpdatePanel on the page. But instead of the standard scenario when the page is completly rendered on the first call I need to display an empty panel content with the loading indicator and start update immediately after the page has been loaded.

How to impelment it?