asp.net客户端IP跟踪

        /// <summary>
        /// 获取客户端IP地址（无视代理）
        /// </summary>
        /// <returns>若失败则返回回送地址</returns>
        public static string GetWebClientIp()
        {
            string userHostAddress = HttpContext.Current.Request.UserHostAddress;

            if (HttpContext.Current.Request.ServerVariables["HTTP_VIA"] != null) // using proxy 
            {
                userHostAddress = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"].ToString(); // Return real client IP. 
            } 
            if (string.IsNullOrEmpty(userHostAddress))
            {
                userHostAddress = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
            }

            //最后判断获取是否成功，并检查IP地址的格式（检查其格式非常重要）
            if (!string.IsNullOrEmpty(userHostAddress) && IsIP(userHostAddress))
            {
                return userHostAddress;
            }
            return "127.0.0.1";
        }

        /// <summary>
        /// 检查IP地址格式
        /// </summary>
        /// <param name="ip"></param>
        /// <returns></returns>
        public static bool IsIP(string ip)
        {
            return System.Text.RegularExpressions.Regex.IsMatch(ip,
                @"^((2[0-4]d|25[0-5]|[01]?dd?).){3}(2[0-4]d|25[0-5]|[01]?dd?)$");
        }