How do I unsubscribe all handlers from an event for a particular class in C#?

Question

Basic premise:

I have a Room which publishes an event when an Avatar \"enters\" to all Avatars within the Room. When an Avatar leaves the Room I want it to remove a

Answer 1

What I'd like to do is in debug (do not think that this is good performance wise for release and one should catch it during development) throw exceptions when a class's events are not unsubscribed, this is the method that I use:

#if DEBUG
private void CheckEventHasNoSubscribers(Delegate eventDelegate)
{
    if (eventDelegate != null)
        if (eventDelegate.GetInvocationList().Length != 0)
        {
            var subscriberCount = eventDelegate.GetInvocationList().Length;

            // determine the consumers of this event
            var subscribers = new StringBuilder();
            foreach (var del in eventDelegate.GetInvocationList())
                subscribers.AppendLine((subscribers.Length != 0 ? ", " : "") + del.Target);

            // throw an exception listing all current subscription that would hinder GC on them!
            throw new Exception(
                $"Event:{eventDelegate.Method.Name} still has {subscriberCount} subscribers, with the following targets [{subscribers}]");
        }
}

#endif

The in my Dispose of the item that owns the delegate, or any other location where you're workflow supposed to release the object I would call it like this.

protected virtual void Dispose(bool disposing)
{
    if (!disposedValue)
    {
        if (_orderCacheLock != null)
            _orderCacheLock.Dispose();

        if(_SettingTradeTimeOut!=null)
            _SettingTradeTimeOut.Dispose();

        _orderCacheLock = null;
#if DEBUG
        CheckEventHasNoSubscribers(OnIsProfitable);
        CheckEventHasNoSubscribers(OnPropertyChanged);
#endif
        disposedValue = true;
    }
}

It's then super easy to find the subscribers to these "orphaned" events and fix the code

ps: An Extension of this "practice pattern" looks like this.

public static void CheckEventHasNoSubscribers(this Delegate eventDelegate)
{
    if (eventDelegate != null)
        if (eventDelegate.GetInvocationList().Length != 0)
        {
            var subscriberCount = eventDelegate.GetInvocationList().Length;
        // determine the consumers of this event
        var subscribers = new StringBuilder();
        foreach (var del in eventDelegate.GetInvocationList())
            subscribers.AppendLine((subscribers.Length != 0 ? ", " : "") + del.Target);

        // point to the missing un-subscribed events
        throw new Exception( $"Event:{eventDelegate.Method.Name} still has {subscriberCount} subscribers, with the following targets [{subscribers}]");
    }

}