.net 获取IP

/// <summary>
        /// 获取IP
        /// </summary>
        /// <returns></returns>
        private string GetIP()
        {
            string ip = string.Empty;
            if (!string.IsNullOrEmpty(System.Web.HttpContext.Current.Request.ServerVariables["HTTP_VIA"]))
                ip = Convert.ToString(System.Web.HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"]);
            if (string.IsNullOrEmpty(ip))
                ip = Convert.ToString(System.Web.HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"]);
            return ip;
        }