public async Task <Rental> endExistingActiveRental(int id) { var rental = context.Rentals.Find(id); rental.RentalEnd = DateTime.Now; rental.TotalCostsInEuro = calculator.calculateRentalPrice(rental.RentalBegin, rental.RentalEnd.Value, rental.Bike.RentalPriceInEuroForFirstHour, rental.Bike.RentalPriceInEuroForEachAdditionalHour); await context.SaveChangesAsync(); return(rental); }