static void Main(string[] args) { while (true) { var commandsPro = new Processing(); var commandsRep = new repository(); Console.WriteLine("Enter Command"); string ReadLine = Console.ReadLine(); switch (ReadLine) { case "Add User": commandsPro.AddUser(); break; case "Add Author": commandsPro.AddAuthor(); break; case "Print All db": commandsRep.AllDB(); break; } } }