static void Main(string[] args) { Mediator mediator = new Mediator(); Teacher arif = new Teacher(mediator); Student orhan = new Student(mediator); Student ishak = new Student(mediator); orhan.Name = "Orhan"; ishak.Name = "İshak"; mediator.Teacher = arif; mediator.Students = new List <Student> { orhan, ishak }; arif.SendImageUrl("slide1.jpg"); Console.WriteLine("-----------------"); ishak.SendQuestion("Is it true ?", ishak); Console.WriteLine("-----------------"); arif.SendAnswer("Yes, this is true", ishak); Console.ReadLine(); }