public void AddBook(Book aBook) { if (LookupBook(aBook.GetISBN()) != null) { Console.WriteLine($"ISBN {aBook.GetISBN()} er allerede i brug!"); } else { books.Add(aBook); Console.WriteLine($"Bogen {aBook.GetISBN()} er tilføjet!"); } books.Add(aBook); // Add code that can add the given Book object to the list }
public void AddBook(Book aBook) { books.Add(aBook.GetISBN(), aBook); }