获取连接的用户ip

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(".") == -1)    //没有“.”肯定是非IPv4格式 
                    result = null;
                else
                {
                    if (result.IndexOf(",") != -1)
                    {
                        //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 = 0; i < temparyip.Length; i++)
                        {
                            if (IsIPAddress(temparyip[i])
                                && temparyip[i].Substring(0, 3) != "10."
                                && temparyip[i].Substring(0, 7) != "192.168"
                                && temparyip[i].Substring(0, 7) != "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|((1d{2})|([1-9]?d))).){3}(?:25[0-5]|2[0-4]d|((1d{2})|([1-9]?d))))");
            if (rx.IsMatch(ip))
            {
                return true;
            }
            return false;
        }