public static bool IsValidTrQueryString(string queryString, BraintreeService service) { var delimiters = new string[1]; delimiters[0] = "&hash="; string[] dataSections = queryString.TrimStart('?').Split(delimiters, StringSplitOptions.None); return dataSections[1] == new Sha1Hasher().HmacHash(service.PrivateKey, dataSections[0]).ToLower(); }