One Simple Domain Event Publisher

DomainEvents.cs

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

namespace Core.DomainEvents
{
    public interface IDomainEvent
    {
        
    }

    public interface IDomainEventSubscriber<in TDomainEvent> where TDomainEvent : IDomainEvent
    {
        void Handle(TDomainEvent domainEvent);
    }

    public class DomainEventPublisher
    {
        private readonly HashSet<object> subscribers = new HashSet<object>();
        
        private DomainEventPublisher()
        {
            
        }

        public void Publish<TDomainEvent>(TDomainEvent domainEvent) where TDomainEvent : IDomainEvent
        {
            IEnumerable<object> validSubscribers = this.subscribers.Where(r => r is IDomainEventSubscriber<TDomainEvent>);

            foreach (IDomainEventSubscriber<TDomainEvent> subscriber in validSubscribers)
            {
                subscriber.Handle(domainEvent);
            }
        }

        public void Register<TDomainEvent>(IDomainEventSubscriber<TDomainEvent> subscriber) where TDomainEvent : IDomainEvent
        {
            this.subscribers.Add(subscriber);
        }

        private static DomainEventPublisher domainEventPublisherInstance;
        
        public static DomainEventPublisher Instance
        {
            get
            {
                if (domainEventPublisherInstance == null)
                {
                    domainEventPublisherInstance = new DomainEventPublisher();
                }

                return domainEventPublisherInstance;
            }
        }
    }
}