private static void CarsManagement() { ICarCategoriesRepository carCategoriesRepository = new CarCategoriesRepository(); var firstCarCategory = carCategoriesRepository.GetAllCategories().First(); ICarsRepository carsRepository = new CarsRepository(); var firstCarId = carsRepository.InsertCar(new Car { CategoryId = firstCarCategory.Id, Fuel = Fuel.Petrol, NumberOdSeats = 5, NumberOfWheels = 4 }); carsRepository.InsertCar(new Car { CategoryId = firstCarCategory.Id, Fuel = Fuel.Petroleum, NumberOdSeats = 2, NumberOfWheels = 4, EngineDetails = new EngineDetails { EngineSize = 1800, NumberOfGears = 6 }, PartBrands = new Collection <PartBrand> { new PartBrand { Name = "Mercedes" }, new PartBrand { Name = "BMW" } } }); var firstCategory = carCategoriesRepository.GetCategoryById(firstCarCategory.Id); }