A fail-fast lightweight event Event Aggregator for Pub/Sub

EventAggregator.cs

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

// From https://www.youtube.com/channel/UCHg8bDmXIYKAwvyc4yMGuUw
namespace Lang.Utility 
{
    public interface IEvent {}

    public class EventAggregator 
    {
        static EventAggregator instance;
        public static EventAggregator Instance
        {
            get 
            {
                if (instance == null) instance = new EventAggregator();
                return instance;
            }
        }

        private readonly IDictionary<Type, IList<Action<IEvent>>> subscriptions = new Dictionary<Type, IList<Action<IEvent>>>();

        public void Publish<T>(T eventContext)
            where T : IEvent
        {
            var myEventType = typeof(T);

            if(subscriptions.ContainsKey(myEventType))
            {
                foreach(var action in subscriptions[myEventType])
                {
                    action(eventContext);
                }
            }
        }

        public void Subscribe<T>(Action<T> action)
            where T : IEvent
        {
            var myEventType = typeof(T);
            
            if (!subscriptions.ContainsKey(myEventType))
            {
                subscriptions.Add(myEventType, new List<Action<IEvent>>());
            }
            subscriptions[myEventType].Add(x => action((T)x));
        }
    }
}

// Usage
public class TestAggregator 
{
    public void Test()
    {
        EventAggregator.Instance.Subscribe<MyEvent>(MyCallBack);
        EventAggregator.Instance.Publish(new MyEvent());
    }

    void MyCallBack(MyEvent context)
    {
      // Do your work
    }

    public class MyEvent : IEvent {}
}