public void AddAirline(string airlineName) { if (airlineValidator.ValidateAirlineName(airlineName)) { if (!airlineRepository.AirlineExists(airlineName)) { this.airlineRepository.AddAirline(airlineName); this.Message = $"Airline {airlineName} successfully added"; } else { this.Message = $"Oops, airline {airlineName} already exists!"; } } else { this.Message = this.airlineValidator.Message; } }