获取用户IP

  /// <summary>
        /// 获取IP
        /// </summary>
        /// <returns></returns>
        private string GetIp()
        {
            string ip = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
            if (ip == null || ip.Length == 0 || ip.ToLower().IndexOf("unknown") > -1)
            {
                ip = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
            }
            return ip;
        }