c# 获取本机公网ip

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Net;
using System.IO;
using System.Text;

public partial class qqqqqqqqqqqq : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
         string strUrl = "http://www.ip138.com/ip2city.asp"; //获得IP的网址了

            Uri uri = new Uri(strUrl);
            WebRequest wr = WebRequest.Create(uri);
            Stream s = wr.GetResponse().GetResponseStream();
            StreamReader sr = new StreamReader(s, Encoding.Default);
            string all = sr.ReadToEnd(); //读取网站的数据

            int i = all.IndexOf("[") + 1;
            string tempip = all.Substring(i, 15);
            string ip = tempip.Replace("]", "").Replace(" ", "");
            Label1.Text = ip;

    }
}