public static string GetIP()
{
　　return System.Web.HttpContext.Current.Request.UserHostAddress;
}

2.

public static string GetAddressIP()
{
　　string strUrl = "http://www.ip138.com/ip2city.asp"; //获得IP的网址
　　Uri uri = new Uri(strUrl);
　　WebRequest webreq = WebRequest.Create(uri);
　　Stream s = webreq.GetResponse().GetResponseStream();
　　StreamReader sr = new StreamReader(s, Encoding.Default);
　　string all = sr.ReadToEnd(); //读取网站返回的数据 格式：您的IP地址是：[x.x.x.x]
　　int j = all.IndexOf("[");
　　int k = all.IndexOf("]");
　　string tempip = all.Substring(j + 1, k - j - 1);

　　string ip = tempip.Replace("]", "").Replace(" ", "").Replace("<", "").Replace("http://www.mamicode.com/", ""); //去除杂项找出ip
　　return ip;
}