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<%@ Page Async="true" Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs"
Inherits="Default" Trace="true" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Async pages</title>
</head>
<body>
<form id="form1" runat="server">
<div id="pageContent">
<% = rssData %>
</div>
</form>
</body>
</html>
File: Default.aspx.cs
using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Threading;
using System.Xml;
using System.Net;
using System.IO;
using System.Text;
using System.Xml.XPath;
public partial class Default : System.Web.UI.Page
{
const string RSSFEED = "http://weblogs.asp.net/despos/rss.aspx";
private WebRequest req;
public string rssData;
protected void Page_Load(object sender, EventArgs e)
{
AddOnPreRenderCompleteAsync(
new BeginEventHandler(BeginTask),
new EndEventHandler(EndTask));
}
IAsyncResult BeginTask(object sender, EventArgs e, AsyncCallback cb, object state)
{
Trace.Warn("Begin async: Thread=" +
Thread.CurrentThread.ManagedThreadId.ToString());
req = WebRequest.Create(RSSFEED);
return req.BeginGetResponse(cb, state);
}
void EndTask(IAsyncResult ar)
{
string text;
using (WebResponse response = req.EndGetResponse(ar))
{
StreamReader reader;
using (reader = new StreamReader(response.GetResponseStream()))
{
text = reader.ReadToEnd();
}
rssData = ProcessFeed(text);
}
Trace.Warn("End async: Thread=" +
Thread.CurrentThread.ManagedThreadId.ToString());
}
string ProcessFeed(string feed)
{
StringBuilder sb = new StringBuilder();
XmlDocument doc = new XmlDocument();
doc.LoadXml(feed);
XPathNavigator nav = doc.CreateNavigator();
XPathNodeIterator iterator;
iterator = nav.Select("/rss/channel/title");
iterator.MoveNext();
sb.AppendFormat("<h3>{0}</h3>", iterator.Current.Value);
iterator = nav.Select("/rss/channel/description");
iterator.MoveNext();
sb.AppendFormat("<i>{0}</i>", iterator.Current.Value);
XmlNodeList items = doc.SelectNodes("/rss/channel/item");
sb.Append("<ul>");
foreach (XmlNode n in items)
{
XmlNode title = n.SelectSingleNode("title");
XmlNode link = n.SelectSingleNode("link");
XmlNode date = n.SelectSingleNode("pubDate");
sb.AppendFormat("<li><a href=\"{0}\">{1}</a> on {2}</li>", link.InnerText, title.InnerText, date.InnerText);
}
sb.Append("</ul>");
return sb.ToString();
}
}
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