IP地址工具類

  /// <summary>
        /// 獲取客戶端IP地址
        /// </summary>
        /// <returns></returns>
        public static string GetHostAddress()
        {
            string userHostAddress = HttpContext.Current.Request.UserHostAddress;
            if (string.IsNullOrEmpty(userHostAddress))
            {
                userHostAddress = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
            }

            //最後判斷獲取是否成功，並檢查IP地址的格式（檢查其格式很是重要）
            if (!string.IsNullOrEmpty(userHostAddress) && IsIP(userHostAddress))
            {
                return userHostAddress;
            }
            return "127.0.0.1";
        }

        public static bool IsIP(string ip)
        {
            return System.Text.RegularExpressions.Regex.IsMatch(ip, @"^((2[0-4]\d|25[0-5]|[01]?\d\d?)\.){3}(2[0-4]\d|25[0-5]|[01]?\d\d?)$");
        }