public static string GetUserIP()

        {

            string result = String.Empty;

            result = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];

            if (result != null && result != String.Empty)

            {

                //可能有代理

                if (result.IndexOf(".") == -)    //没有“.”肯定是非IPv4格式

                    result = null;

                else

                {

                    if (result.IndexOf(",") != -)

                    {

                        //有“,”，估计多个代理，取第一个不是内网的IP。

                        result = result.Replace(" ", "").Replace("'", "");

                        string[] temparyip = result.Split(",;".ToCharArray());

                        for (int i = ; i < temparyip.Length; i++)

                        {

                            if (IsIPAddress(temparyip[i])

                                && temparyip[i].Substring(, ) != "10."

                                && temparyip[i].Substring(, ) != "192.168"

                                && temparyip[i].Substring(, ) != "172.16.")

                            {

                                return temparyip[i];    //找到不是内网的地址

                            }

                        }

                    }

                    else if (IsIPAddress(result)) //代理即是IP格式

                        return result;

                    else

                        result = null;    //代理中的内容 非IP，取IP

                }

            }

            if (null == result || result == String.Empty)

            {

                result = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];

                if (result == "::1")

                    result = "127.0.0.1";

            }

            return result;

        } 

        public static bool IsIPAddress(string ip)

        {

            Regex rx = new Regex(@"((?:(?:25[0-5]|2[0-4]\d|((1\d{2})|([1-9]?\d)))\.){3}(?:25[0-5]|2[0-4]\d|((1\d{2})|([1-9]?\d))))");

            if (rx.IsMatch(ip))

            {

                return true;

            }

            return false;

        }