private string getGasCarToFuelRegNum() { string registrationNumber = string.Empty; eFuelType fuelType = eFuelType.None; registrationNumber = getExistingRegistrationNumberFromUser(); if (m_Garage.CheckIfFueableCar(registrationNumber) == true) { fuelType = getFuelTypeInput(); if (m_Garage.CheckIfValidFuelType(registrationNumber, fuelType) == false) { throw new ArgumentException("Invalid_Fuel_Type"); } } else { throw new ArgumentException("Not_Fuelable_Vehicle"); } return(registrationNumber); }