获取客户端IP地址

/// <summary>
        /// 获取客户端IP地址
        /// </summary>
        /// <param name="request"></param>
        /// <returns></returns>
        public static string GetIpAddr(HttpRequest request)
        {
            string ip = request.ServerVariables["HTTP_X_FORWARDED_FOR"];

            if (string.IsNullOrEmpty(ip) || "unknown".Equals(ip, StringComparison.CurrentCultureIgnoreCase))
            {
                ip = request.ServerVariables["Proxy-Client-IP"];
            }
            if (string.IsNullOrEmpty(ip) || "unknown".Equals(ip, StringComparison.CurrentCultureIgnoreCase))
            {
                ip = request.ServerVariables["WL-Proxy-Client-IP"];
            }
            if (string.IsNullOrEmpty(ip) || "unknown".Equals(ip, StringComparison.CurrentCultureIgnoreCase))
            {
                ip = request.ServerVariables["HTTP_CLIENT_IP"];
            }
            if (string.IsNullOrEmpty(ip) || "unknown".Equals(ip, StringComparison.CurrentCultureIgnoreCase))
            {
                ip = request.ServerVariables["REMOTE_ADDR"];
            }
            if (string.IsNullOrEmpty(ip) || "unknown".Equals(ip, StringComparison.CurrentCultureIgnoreCase))
            {
                ip = "";
            }
            if (!string.IsNullOrEmpty(ip) && ip.IndexOf(",", StringComparison.Ordinal) != -1 && ip.Length > 6)
            {
                ip = ip.Split(',')[0];
            }
            return ip;
        }