ASP.NET(c#)获取外网IP，通过网页抓取方式

public static string Get_Ip()
 {
            WebRequest request = WebRequest.Create("http://iframe.ip138.com/ic.asp");
            WebResponse response = request.GetResponse();
            StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding("gb2312"));
            string read = reader.ReadToEnd();
            Regex regex = new Regex("<center>(?<title>.*?)</center></body></html>");
            string ip = "";
            if (regex.IsMatch(read))
            {
                read = regex.Match(read).Groups["title"].Value;
                string[] arr = read.Split('[');
                ip = arr[1].Split(']')[0];
            }
            return ip;

}