CleanArch.DevKit.Mediator.Domain 0.1.0-preview.1

CleanArch.DevKit.Mediator.Domain

Bridge between CleanArch.DevKit.Domain and CleanArch.DevKit.Mediator. Provides IDomainEventNotification (a domain event that also flows through the mediator pipeline) and a PublishDomainEventsAsync extension on IMediator that dispatches each buffered event with its concrete runtime type — so handlers registered for the specific event class are picked up.

Part of the CleanArch.DevKit toolkit.

Install

dotnet add package CleanArch.DevKit.Mediator.Domain

Pulls in CleanArch.DevKit.Domain and CleanArch.DevKit.Mediator transitively.

Quick start

// 1. Mark events that should reach the mediator pipeline.
public sealed record UserRegistered(Guid UserId, string Email) : IDomainEventNotification;

// 2. Aggregate raises the event during command processing.
public sealed class User : AggregateRoot<Guid>
{
    private User(Guid id, string email) : base(id)
        => Raise(new UserRegistered(id, email));

    public static User Register(string email) => new(Guid.NewGuid(), email);
}

// 3. Handler for the event (regular mediator notification handler).
public sealed class SendWelcomeEmail : INotificationHandler<UserRegistered>
{
    public Task Handle(UserRegistered evt, CancellationToken ct)
        => SendEmail(evt.Email, ct);
}

// 4. Unit of work drains the buffer and publishes after commit.
public sealed class CreateUserHandler(IMediator mediator, IUserRepository repo)
    : IRequestHandler<CreateUserCommand, Guid>
{
    public async Task<Guid> Handle(CreateUserCommand cmd, CancellationToken ct)
    {
        var user = User.Register(cmd.Email);
        await repo.SaveAsync(user, ct);
        await mediator.PublishDomainEventsAsync(user, ct);
        return user.Id;
    }
}

Why a typed dispatch?

IMediator.Publish<TNotification> is generic on the static type. If you wrote:

foreach (var evt in aggregate.DomainEvents)
    await mediator.Publish(evt, ct); // <-- dispatches as INotification, not UserRegistered

…the call captures TNotification = INotification at compile time and no concrete handler matches. PublishDomainEventsAsync uses a cached MakeGenericMethod per runtime type so the correct typed Publish<UserRegistered> is invoked.

What gets published?

PublishDomainEventsAsync iterates aggregate.DomainEvents and dispatches only events that also implement INotification — typically via IDomainEventNotification. Events that are IDomainEvent only are dropped from the buffer without being published. This lets you keep internal/audit-only events in the aggregate without spam-publishing them through the mediator.

The buffer is cleared in either case, so a follow-up PublishDomainEventsAsync won't re-publish the same events.

License

MIT — see LICENSE.