private static void AddCard(ref DeckService deckService) { Console.WriteLine("Enter the name of the deck: "); var name = Console.ReadLine(); var deck = deckService.GetDeck(name); if (deck == null) { Console.WriteLine("The deck not found.\n"); return; } Console.WriteLine("\n\nEnter a name for the new card: "); name = Console.ReadLine(); ushort number; try { Console.WriteLine("\nEnter the number of the card: "); number = ushort.Parse(Console.ReadLine() !); } catch (Exception) { Console.WriteLine("Input error.\n"); return; } var result = DeckService.AddCard(ref deck, name, number); Console.WriteLine(result.Message); }