public string Validate() { var appIdDigits = appId.GetDigitsQuantity(); if (ProfileId.GetDigitsQuantity() != 17) { return("Profile Id must to contain of 17 digits"); } else if (frequency < 5) { return("Frequency must to be positive and more than 5 seconds"); } else if (appIdDigits < 3 || appIdDigits > 6) { return("App Id must to be between 3 and 6 digits"); } return(string.Empty); }