判断QQ的在线状态

 大家可以打开这个URL看看
http://wpa.qq.com/pa?p=1:你的QQ:3

如http://wpa.qq.com/pa?p=1:283984419:3

using System.Net;
using System;

public class QQUtility
{
    public static bool IsOnline(string qq)
    {
        //283984419
        string url = string.Format("http://wpa.qq.com/pa?p=1:{0}:3", qq);
        HttpWebRequest request = (HttpWebRequest) WebRequest.Create(url);
        request.Headers.Set("Pragma", "no-cache");
        HttpWebResponse HttpWResp = (HttpWebResponse) request.GetResponse();

        //"/rtx_offline.gif""/rtx_online.gif"
        string query = HttpWResp.ResponseUri.PathAndQuery;

        switch (query)
        {
        case "/rtx_offline.gif":
        return false;
        //break;
        case "/rtx_online.gif":
        return true;
        //break;
        default:
        return true;
        }
    }

}
class test
{
    static void Main()
    {
        Console.WriteLine(QQUtility.IsOnline("283984419"));
        Console.Read();
    }
}