Winform中如何讀取局域網路由的IP地址代碼

System.Net.WebClient client = new System.Net.WebClient();
client.Encoding = System.Text.Encoding.Default;
string lip = client.DownloadString("http://www.ip138.com/ip2city.asp");
string sip = reply.Substring(reply.IndexOf("您的IP地址是"), reply.IndexOf("</center>") - reply.IndexOf("您的IP地址是"));
MessageBox.Show(sip);