ASP.NET获取用户端的真实IP

ASP.NET获取用户端的真实IP在各种场景都能用到，但是用户网端变幻莫测情况众多，获取真实IP还真是不容易啊。
下面分享个比较好一点的方法:

获取IP初始版本

/// <summary>
        /// 获得当前页面客户端的IP
        /// Author:codeo.cn
        /// </summary>
        /// <returns>当前页面客户端的IP</returns>
        public static string GetIP()
        {
            string result = String.Empty;
            result = HttpContext.Current.Request.ServerVariables["HTTP_CDN_SRC_IP"];
            if (string.IsNullOrEmpty(result))
                result = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];

            if (string.IsNullOrEmpty(result))
                result = HttpContext.Current.Request.UserHostAddress;

            if (string.IsNullOrEmpty(result) || !Utils.IsIP(result))
                return "127.0.0.1";

            return result;
        }
        /// <summary>
        /// 是否为ip
        /// Author:codeo.cn
        /// </summary>
        /// <param name="ip"></param>
        /// <returns></returns>
        public static bool IsIP(string ip)
        {
            return Regex.IsMatch(ip, @"^((2[0-4]d|25[0-5]|[01]?dd?).){3}(2[0-4]d|25[0-5]|[01]?dd?)$");
        }

改进版获取用户真实IP

/// <summary>
        /// 取得客户端真实IP。如果有代理则取第一个非内网地址
        /// Author:codeo.cn
        /// </summary>
        /// <returns></returns>
        public static string GetIPAddress()
        {
            string strresult = string.Empty;
            strresult = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
            if (strresult != null && strresult != string.Empty)
            {
                //可能有代理  
                if (strresult.IndexOf(".") == -1)    //没有“.”肯定是非IPv4格式  
                {
                    strresult = null;
                }
                else
                {
                    if (strresult.IndexOf(".") != -1)
                    {
                        //有“,”，估计多个代理。取第一个不是内网的IP。    
                        strresult = strresult.Replace(" ", "").Replace("'", "");
                        string[] strarrtemparyip = strresult.Split(",;".ToCharArray());

                        for (int i = 0; i < strarrtemparyip.Length; i++)
                        {
                            if (IsIPAddress(strarrtemparyip[i]) && strarrtemparyip[i].Substring(0, 3) != "10." && strarrtemparyip[i].Substring(0, 7) != "192.168" && strarrtemparyip[i].Substring(0, 7) != "172.16.")
                            {
                                return strarrtemparyip[i];    //找到不是内网的地址  
                            }
                        }
                    }
                    else if (IsIPAddress(strresult))    //代理即是IP格式  
                    {
                        return strresult;
                    }
                    else
                    {
                        strresult = null;       //代理中的内容 非IP，取IP
                    }
                }
            }
            string strIpAddress = (HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"] != null && HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"] != string.Empty ? HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"] : HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"]);

            if (null == strresult || strresult == string.Empty)
            {
                strresult = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
            }
            if (strresult == null || strresult == string.Empty)
            {
                strresult = HttpContext.Current.Request.UserHostAddress;
            }

            return strresult;
        }
        /// <summary>
        /// 判断是否是IP地址格式 0.0.0.0 
        /// Author:codeo.cn  
        /// </summary>
        /// <param name="strIp">待判断的IP地址</param>
        /// <returns>true or false</returns>
        private static bool IsIPAddress(string strIp)
        {
            if (strIp == null || strIp == string.Empty || strIp.Length < 7 || strIp.Length > 15)
            {
                return false;
            }

            string strRegformat = @"^d{1,3}[.]d{1,3}[.]d{1,3}[.]d{1,3}___FCKpd___0quot";

            Regex regex = new Regex(strRegformat, RegexOptions.IgnoreCase);

            return regex.IsMatch(strIp);
        }