列表1:ProgressBar.cs

public class ProgressBar : System.Web.UI.Control,
System.Web.UI.ICallbackEventHandler{
private int PercentCompleted{
　get
　{
　　if System.Web.HttpContext.Current.Session
　　["PercentComplete"] == null) {
　　　System.Web.HttpContext.Current.Session
　　　　["PercentComplete"] = 1;
　}　
　else {
　　System.Web.HttpContext.Current.Session["PercentComplete"] =
　　(int)System.Web.HttpContext.Current.Session["PercentComplete"] + 1;
　}
　return (int)System.Web.HttpContext.Current.Session["PercentComplete"];
}
set
{
　System.Web.HttpContext.Current.Session["PercentComplete"] = 1;
}
}
public string RaiseCallbackEvent(string eventArguments) {
　int percent = this.PercentCompleted;
　if (percent > 100)
　{
　　this.PercentCompleted = 1;
　　return "completed";
　}
　else
　{
　　return percent.ToString() + "%";
　}
}
protected override void OnPreRender(EventArgs e) {
　this.Page.ClientScript.ReGISterClientScriptBlock(typeof(ProgressBar),
"ProgressBar", this.GetClientSideScript(), true);
　base.OnPreRender(e);
}
protected override void Render(HtmlTextWriter writer) {
　System.Text.StringBuilder sb = new StringBuilder();
　sb.Append(@"<table id=""ProgressBarContainer"" bgcolor=""LightSteelBlue""
　border=""0"" width=""400"" style=""DISPLAY:none; POSITION: absolute;
　Z-INDEX: 10"">");
　sb.Append(@"<tr><td colspan=""3"" style=""padding:3px 2px 2px 10px"">");
　sb.Append(@"<font face=""Verdana,Arial,sans-serif"" size=""2"">");
　sb.Append(@"<span id=""ProgressBarLabel"">Uploading...</span>");
　sb.Append(@"</font></td></tr><tr><td>");
　sb.Append(@"<font size=""1""> </font></td><td bgcolor=""#999999""
　width=""100%"">");
　sb.Append(@"<table id=""ProgressBar"" border=""0"" width=""0""
　cellspacing=""0"">");
　sb.Append(@"<tr><td style=""background-image:url(progressbar.gif)"">
　<font size=""1""> </font></td>");
　sb.Append(@"</tr></table></td>");
　sb.Append(@"<td><font size=""1""> </font></td></tr>");
　sb.Append(@"<tr height=""5px""><td colspan=""3""></td></tr>");
　sb.Append(@"</table>");
　writer.Write(sb.ToString());
　base.Render(writer);
}
private string GetClientSideScript() {
　System.Reflection.Assembly dll =
　System.Reflection.Assembly.GetExecutingAssembly();
　StreamReader reader;
　reader = new StreamReader(dll.GetManifestResourceStream
　　("ProgressBar.txt"));
　StringBuilder js = new StringBuilder(reader.ReadToEnd());
　string fp = this.Page.ClientScript.GetCallbackEventReference
　　(this,"","UpdateProgressBar","");
　js.Replace("##InitiateCallBack##",fp);
　reader.Close();
　return js.ToS
tring();
}
}

<script language="javascript">
var isCompleted=false;
//这个函数初始化到服务器端的回调
function DrawProgressBar(){
　##InitiateCallBack##;
　if (!isCompleted) {
　　window.setTimeout('DrawProgressBar()'，200);
　}
　else
　{
　　isCompleted=false;
　　document.getElementById("ProgressBarContainer").style.display = 'none';
　}
}
//当thecallback完成时，下列函数被调用
function UpdateProgressBar(percent){
　if (percent == 'completed'){
　　isCompleted=true;
　}
　else{
　　document.getElementById("ProgressBar").width = percent;
　}
}