HttpWebRequest代理访问网站

private void button1_Click(object sender, EventArgs e)
        {
            string str ="http://www.7y8.com/V/ip.asp";
            MessageBox.Show("访问的IP地址是："+getIPAddr(GetResponseStr(str)));
        }

        //使用代理访问
        private string GetResponseStr(string str)
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(str);
            request.Proxy = CreatProxy("http://65.110.17.142:80","","");
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            Stream stream = response.GetResponseStream();//获得回应的数据流
            //将数据流转成 String
            string result = new StreamReader(stream, System.Text.Encoding.UTF8).ReadToEnd();
            return result;
        }

        /// <summary>
        /// 创建代理对象
        /// </summary>
        /// <param name="str_IP">HTTP代理地址(默认是80端口)</param>
        /// <param name="str_UserName">用户名(匿名则用户名和密码为空)</param>
        /// <param name="str_Pwd">密码</param>
        /// <returns></returns>
        private WebProxy CreatProxy(string str_IP, string str_UserName, string str_Pwd)
        {
            str_IP = str_IP.ToUpper().IndexOf("HTTP://") > -1 ? str_IP : "http://" + str_IP;
            WebProxy myProxy = new WebProxy();
            myProxy.Address = new Uri(str_IP);
            myProxy.Credentials = new NetworkCredential(str_UserName, str_Pwd);
            return myProxy;
        }

        //抓取页面上显示的IP地址
        private string getIPAddr(string str)
        {
            System.Text.RegularExpressions.Regex reg = new System.Text.RegularExpressions.Regex(@"\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}");
            return reg.Match(str).Value.ToString();
        }