asp.net获取访问者ip地址的函数

/// <summary>
   /// 获取IP地址
   /// </summary>
        public static string IPAddress
        {
            get
            {
                string userIP;
                // HttpRequest Request = HttpContext.Current.Request;
                HttpRequest Request = HttpContext.Current.Request; // ForumContext.Current.Context.Request;
                // 如果使用代理，获取真实IP
                if (Request.ServerVariables["HTTP_X_FORWARDED_FOR"] != "")
                    userIP = Request.ServerVariables["REMOTE_ADDR"];
                else
                    userIP = Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
                if (userIP == null || userIP == "")
                    userIP = Request.UserHostAddress;
                return userIP;
            }
        }