ASP.NET 2.0实现AJAX的Web开发(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();

}

}