Code snippets for "Why you should always unsubscribe event handlers" post

s1.cs

public class Publisher
{
    public event EventHandler MyEvent;
 
    public void FireEvent()
    {
        if (MyEvent != null)
        {
            MyEvent(this, EventArgs.Empty);
        }
    }
}

s2.cs

public class BadSubscriber
{
    public BadSubscriber(Publisher publisher)
    {
        publisher.MyEvent += publisher_MyEvent;
    }
 
    void publisher_MyEvent(object sender, EventArgs e)
    {
        Console.WriteLine("the publisher notified the bad subscriber of an event");
    }
}

s3.cs

public class GoodSubscriber : IDisposable
{
    private readonly Publisher publisher;
 
    public GoodSubscriber(Publisher publisher)
    {
        this.publisher = publisher;
        publisher.MyEvent += publisher_MyEvent;
    }
 
    void publisher_MyEvent(object sender, EventArgs e)
    {
        Console.WriteLine("the publisher notified the good subscriber of an event");
    }
 
    public void Dispose()
    {
        publisher.MyEvent -= publisher_MyEvent;
    }
}

s4.cs

static void Main(string[] args)
{
    var publisher = new Publisher();
    var badSubscriber = new BadSubscriber(publisher);
    var goodSubscriber = new GoodSubscriber(publisher);
 
    var badSubscriberRef = new WeakReference(badSubscriber);
    var goodSubscriberRef = new WeakReference(goodSubscriber);
 
    publisher.FireEvent();
 
    badSubscriber = null;
    goodSubscriber.Dispose();
    goodSubscriber = null;
 
    GC.Collect();
 
    Console.WriteLine(goodSubscriberRef.IsAlive ? "good publisher is alive" : "good publisher is gone");
    Console.WriteLine(badSubscriberRef.IsAlive ? "bad publisher is alive" : "bad publisher is gone");
 
    publisher.FireEvent();
}