ASP.NET 2.0实现AJAX的Web开发(1)(2)

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， Helvetica， 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.ToString();
}
}