using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Net;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
public partial class AsyncPageTask : System.Web.UI.Page
{
　private WebRequest _request;
　protected void Page_Load(object sender, EventArgs e)
　{
　　PageAsyncTask task = new PageAsyncTask(
　　　new BeginEventHandler(BeginAsyncOperation),
　　　new EndEventHandler(EndAsyncOperation),
　　　new EndEventHandler(TimeoutAsyncOperation),
　　null
　);
　RegisterAsyncTask(task);
　}
　IAsyncResult BeginAsyncOperation(object sender, EventArgs e,
AsyncCallback cb, object state)
　{
　　_request = WebRequest.Create("http://msdn.microsoft.com");
　　return _request.BeginGetResponse(cb, state);
　}
　void EndAsyncOperation(IAsyncResult ar)
　{
　　string text;
　　using (WebResponse response = _request.EndGetResponse(ar))
　　{
　　　using (StreamReader reader = new StreamReader
(response.GetResponseStream()))
　　　　{
　　　　　text = reader.ReadToEnd();
　　　　}
　　}
　　Regex regex = new Regex("href\\s*=\\s*\"([^\"]*)\"",
RegexOptions.IgnoreCase);
　　MatchCollection matches = regex.Matches(text);
　　StringBuilder builder = new StringBuilder(1024);
　　foreach (Match match in matches)
　　{
　　　builder.Append(match.Groups[1]);
　　　builder.Append("<br/>");
　　}
　　Output.Text = builder.ToString();
　}
　void TimeoutAsyncOperation(IAsyncResult ar)
　{
　　Output.Text = "Data temporarily unavailable";
　}
}