public class EventPublisher
{
    private readonly IList<Func<IHandle>> _subscribers;

    public EventPublisher(IList<Func<IHandle>> subscribers)
    {
        _subscribers = subscribers;
    }

    public void Publish<TPayload>(TPayload payload)
        where TPayload : class
    {
        var payloadHandlers = _subscribers.OfType<Func<IHandle<TPayload>>>();

        foreach (var payloadHandler in payloadHandlers)
        {
            payloadHandler().Handle(payload);
        }
    }
}

var subscribers = new List<Func<IHandle>> {() => new SomeHandler()};
var eventPublisher = new EventPublisher(subscribers);

eventPublisher.Publish(new SomeMessage { Text = "Some random text..." });

public interface IHandle {}

public interface IHandle<TMessage> : IHandle {
    void Handle(TMessage message);
}

var subscribers = new List<Func<IHandle<SomeMessage>>> {() => new SomeHandler()};

public EventPublisher(IEnumerable<Func<IHandle>> subscribers)
{
    _subscribers = subscribers.ToList();
}

public void RegisterHandler(IHandle<TMessage> handler) { ... }