private static void Main(string[] args) { var reservation = new Reservation.Reservation() { Name = "John", LastName = "Galt", Book = new Book.Book() { Name = "BookName", ISBN = "978-3-16-148410-0" } }; var reservationObserver = new ReservationObserver(reservation); foreach (var librarian in GetLibrarians()) { reservationObserver.RegisterObserver(new ReservationSubscriber(librarian)); } reservationObserver.Publish(); reservationObserver.NotifyObservers(); }