static void Main(string[] args)
{
var s1 = new MessageSubscriberOne();
var s2 = new MessageSubscriberTwo();
var s3 = new MessageSubscriberThree();
var p = new MessagePublisher();
p.Attach(s1);
p.Attach(s2);
p.NotifyUpdate(new Message("Fist Message"));
p.Detach(s1);
p.Attach(s3);
p.NotifyUpdate(new Message("Second Message"));
}
