A simple weak event pattern by C# for Game.

EventManager.cs

using System;
using System.Collections.Generic;
using System.Linq;

// Static singleton class.
// There is no necessary to access this class directly.
public class EventManager {

    private static Dictionary<GameEvent, List<WeakReference>> listeners =
        new Dictionary<GameEvent, List<WeakReference>>();

    public static void AddListener(EventListener listener, GameEvent e) {
        if (!listeners.ContainsKey(e)) {
            listeners [e] = new List<WeakReference> ();
        }

        listeners [e].Add (new WeakReference(listener));
    }

    public static void RemoveListener(EventListener listener, GameEvent e) {
        RemoveListener (new WeakReference (listener), e);
    }

    public static void RemoveListener(WeakReference reference, GameEvent e) {
        listeners [e].Remove (reference);
    }

    public static void Trigger(GameEvent e) {
        if (listeners.ContainsKey(e)) {
            listeners [e].ToList().ForEach ((r) => {
                if (r.IsAlive) {
                    ((EventListener)r.Target).on(e);
                } else {
                    RemoveListener(r, e);
                }
            });
        }
    }

}

// Mainly using class.
public class EventListener {

    public readonly Action<GameEvent> on;
    private List<GameEvent> events;

    public EventListener(Action<GameEvent> on) {
        this.on = on;
        events = new List<GameEvent> ();
    }

    // Attach this listener to the event.
    public EventListener Listen(GameEvent e) {
        events.Add (e);
        EventManager.AddListener (this, e);
        return this;
    }

    public void Dispose() {
        events.ForEach((e) => EventManager.RemoveListener(this, e));
    }

}

// This class can be customized.
public class GameEvent {

    public readonly string name;

    public GameEvent(string name) {
        this.name = name;
    }

    public override string ToString() {
        return "GameEvent (" + name + ")";
    }

    public override bool Equals (object obj) {
        if (obj == null || obj.GetType() != GetType()) {
            return false;
        }
        var e = (GameEvent)obj;
        return e.name == name;
    }

    public override int GetHashCode() {
        return name.GetHashCode();
    }

}

Usage

new EventListener ((e) => {
    // do something.
}).Listen(new GameEvent("click"));