public IActionResult Index(CarBoatModel carBoatModel)
 {
     //Check if the model if valid
     if (ModelState.IsValid)
     {
         //Check if the vehicle is a car or boat
         if (carBoatModel.mileage.HasValue)
         {
             //Create a car object
             Car car = new Car(carBoatModel.manufacturer, carBoatModel.model, carBoatModel.productYear.ToString(), carBoatModel.mileage.ToString());
             //Inserts the car object
             DBL.InsertCar(car);
         }
         else
         {
             //Create a boat object
             Boat boat = new Boat(carBoatModel.manufacturer, carBoatModel.model, carBoatModel.productYear.ToString());
             //Inserts the boat object
             DBL.InsertBoat(boat);
         }
         //Return the view
         return(View(new CarBoatModel()));
     }
     else
     {
         //Return the index view with the model
         return(View("Index", carBoatModel));
     }
 }