在C#中订阅事件之前取消订阅事件会发生什么情况？

public class EventPublisher
{
    public event EventHandler MyEvent;

    public void PublishEvent()
    {
        MyEvent?.Invoke(this, EventArgs.Empty);
    }
}

public class EventSubscriber
{
    public void Subscribe(EventPublisher publisher)
    {
        publisher.MyEvent += HandleEvent;
    }

    public void Unsubscribe(EventPublisher publisher)
    {
        publisher.MyEvent -= HandleEvent;
    }

    private void HandleEvent(object sender, EventArgs e)
    {
        Console.WriteLine("Event handled");
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        EventPublisher publisher = new EventPublisher();
        EventSubscriber subscriber = new EventSubscriber();

        subscriber.Subscribe(publisher);
        publisher.PublishEvent();

        subscriber.Unsubscribe(publisher);
        publisher.PublishEvent();
    }
}