Mashape secret code verification (upd)

// updated: 03-04-2013
//

using System.Web;

public static class Mashape // www.mashape.com/priore
    {
        private static string[] VALID_MASHAPE_ADDR = new string[] { "23.21.64.131", "23.21.68.63", "23.23.86.71", "23.23.87.232", "23.23.103.203", "23.23.103.204", "23.23.103.207", "23.23.103.212", "23.23.103.218", "50.17.255.165" };

        public static bool IsValidSecretCode(string secret_code)
        {
            HttpContext context = HttpContext.Current;
            if (context == null)
                throw new ArgumentException("Invalid HTTP Context!");
            return IsValidSecretCode(secret_code, context);
        }

        public static bool IsValidSecretCode(string secret_code, HttpContext context)
        {
            string keySecret = "HTTP_X_MASHAPE_PROXY_SECRET:" + secret_code;
            string tagSubscr = "HTTP_X_MASHAPE_SUBSCRIPTION:";

            HttpRequest request = context.Request;
            string remote_addr = request.ServerVariables["REMOTE_ADDR"];
            string all_http = request.ServerVariables["ALL_HTTP"];
            return VALID_MASHAPE_ADDR.Contains(remote_addr) && all_http.Contains(keySecret) && all_http.Contains(tagSubscr);
        }
    }