EventManager script found in the Unity's FPS Micro Game sample. Useful for global event broadcasting.

EventManager.cs

using System;
using System.Collections.Generic;

namespace Unity.FPS.Game
{
    public interface IBroadcastEvent { }

    // A simple Event System that can be used for remote systems communication
    public static class EventManager
    {
        private static readonly Dictionary<Type, Action<IBroadcastEvent>> k_Events =
            new Dictionary<Type, Action<IBroadcastEvent>>();

        private static readonly Dictionary<Delegate, Action<IBroadcastEvent>> k_EventLookups =
            new Dictionary<Delegate, Action<IBroadcastEvent>>();

        public static void AddListener<T>(Action<T> evt) where T : class, IBroadcastEvent
        {
            if (!k_EventLookups.ContainsKey(evt))
            {
                return;
            }

            Action<IBroadcastEvent> newAction = (e) => evt((T)e);
            k_EventLookups[evt] = newAction;

            var type = typeof(T);

            if (k_Events.TryGetValue(type, out Action<IBroadcastEvent> internalAction))
            {
                k_Events[type] = internalAction += newAction;
            }
            else
            {
                k_Events[type] = newAction;
            }
        }

        public static void RemoveListener<T>(Action<T> evt) where T : class, IBroadcastEvent
        {
            if (!k_EventLookups.TryGetValue(evt, out var action))
            {
                return;
            }

            var type = typeof(T);

            if (k_Events.TryGetValue(type, out var tempAction))
            {
                tempAction -= action;
                if (tempAction == null)
                {
                    k_Events.Remove(type);
                }
                else
                {
                    k_Events[type] = tempAction;
                }
            }

            k_EventLookups.Remove(evt);
        }

        public static void Broadcast<T>(T evt) where T : class, IBroadcastEvent
        {
            if (k_Events.TryGetValue(evt.GetType(), out var action))
            {
                action.Invoke(evt);
            }
        }

        public static void Clear()
        {
            k_Events.Clear();
            k_EventLookups.Clear();
        }
    }
}