How to display progress bar for long running page in Javascript

Discussion in 'ASP .Net' started by Anonieko, Feb 4, 2006.

  1. Anonieko

    Anonieko Guest

    Query: How to display progress bar for long running page


    Yet another solution. REFERENCE:

    My only regret is that when click the browser back button, it loads the
    progress bar again.
    Any solution to this?
    Anonieko, Feb 4, 2006
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  2. Anonieko

    ElronVel Guest

    here is the code

    ------Article highlights

    There are probably half a dozen or more ways to accomplish this task,
    including using a hidden IFRAME with Remote Scripting, using the
    XMLHTTP COM object from the client side (a technique that is actually
    used in ASP.NET 2.0 with partial page caching and callbacks), using
    popup windows, and other little tricks. The one I present here is one
    of the simplest. It uses an intermediate page with some timed script on
    the client side that has actually loaded the destination page with the
    long running process in the background. All you do is have a button or
    hyperlink in the page that wants to call the long - running page which
    really loads the intermediate script page, and has the real destination
    page on the querystring, like so:

    <A HREF="ProgressPage.aspx?destPage=EndPage.aspx">Kick off long running

    The "ProgressPage.aspx" has client script that looks like this:

    <title>Loading, please wait...</title>
    var ctr = 1;
    var ctrMax = 50; // how many is up to you-how long does your end page
    var intervalId;
    function Begin()
    //set this page's window.location.href to the target page
    window.location.href = "<%= Request.QueryString["destPage"]%>";
    // but make it wait while we do our progress...
    intervalId = window.setInterval("ctr=UpdateIndicator(ctr, ctrMax)",
    function End() {
    // once the interval is cleared, we yield to the result page (which
    has been running)

    function UpdateIndicator(curCtr, ctrMaxIterations)
    curCtr += 1;
    if (curCtr <= ctrMaxIterations) { =curCtr*10 +"px";
    return curCtr;
    { =0;
    return 1;
    <body onload="Begin()" onunload="End()">
    <form id="Form1" method="post" runat="server">
    <div align=center><h3>Loading Data, please wait...</h3></div>
    <table id=indicator border="0" cellpadding="0" cellspacing="0"
    width="0" height="20" align="center" >
    <td align="center" bgcolor=red width="100%"></td>

    What the above script does is as follows:

    In Body onload, Begin() is called. This immediately sets the
    location.href property of the window to the final page, which begins
    loading immediately in the background while the rest of the script
    We set the intervalId variable to the call to
    window.setInterval("ctr=UpdateIndicator(ctr, ctrMax)", 500); which sets
    a timed call to the UpdateIndicator method every 500 milliseconds.
    UpdateIndicator increments the ctr variable and increase the DHTML
    width of table "indicator' to the value of ctr * 10 pixels. This is
    client side DHTML code so it executes in the browser immediately.
    When the target page has completed loading, the onUnload event is
    called and the interval timer is cleared in the End() method Your end
    page will then take over and you will see the result.
    In my Endpage.aspx, the page with the long running process, I've put in
    a routine that actually does some real work that takes time (instead of
    Thread.Sleep(xxx) which most examples would show):

    private void Page_Load(object sender, System.EventArgs e)
    //Kick off your long running process here...
    // this is just a surrogate for whatever long running
    //process your page does.
    WebClient wc= new WebClient();
    for(int i= 1; i<40;i++)
    byte[] b=wc.DownloadData("");
    Response.Write("<li>Got Microsoft " + i.ToString()+" Length: " +

    The above code uses the WebClient class to request the Microsoft home
    page 40 times, and each time the result comes back, it adds a line with
    some info to an unordered list.

    The result of all this is that when the user clicks the link to go to
    the long-running page, they will first see our Progress page with a red
    indicator that steadily increases in width until the target page has
    completed processing:
    ElronVel, Feb 4, 2006
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