I am trying to play around a little with MediatR and MassTransit, in fact I’m trying to make a WebAPI developed as a Modular Monolith using a slightly modified version of Clean Architecture (Applicaiton, Domain, Infrastructure, Persistance), my core idea is to use MediatR.INotification as a DomainEvent (in-domain comunication) and MassTransit for Integration events (module to module comunication)

My Setup regarding masstransit and mediatr:

services.AddMassTransit(configure =>
{
    configure.SetKebabCaseEndpointNameFormatter();
    configure.UsingInMemory((context, cfg) => cfg.ConfigureEndpoints(context));
});

// This correctly registres the service INotificationHandler<AddedRegistryDomainEvent>
services.AddMediatR(cfg =>
{
    cfg.RegisterServicesFromAssembly(typeof(Modules.Registry.Application.AssemblyReference).Assembly);
});

//Verified by breakpointing in setup before app.Run()
var x = app.Services.GetServices<INotificationHandler<AddedRegistryDomainEvent>>().ToList();

This is my ICommandHandler.Handle metho

public async Task<RegistryDTO> Handle(AddRegistryCommand request, CancellationToken cancellationToken)
{
    string denomination = string.Empty;
    if (request.Registry.IsPerson)
    {
        denomination = $"{request.Registry.FirstName} {request.Registry.LastName}";
    }
    if (request.Registry.IsCompany)
    {
        denomination = $"{request.Registry.CompanyName} {request.Registry.LegalName}";
    }

    await _repository.BeginTransactionAsync(cancellationToken);

    var entity = new RegistryEntity()
    {
        FirstName = request.Registry.FirstName,
        LastName = request.Registry.LastName,
        CompanyName = request.Registry.CompanyName,
        LegalName = request.Registry.LegalName,
        Denomination = denomination,
        IsPerson = request.Registry.IsPerson,
        IsCompany = request.Registry.IsCompany,
        IsCustomer = request.Registry.IsCustomer,
        IsSupplier = request.Registry.IsSupplier,
        IsNetwork = request.Registry.IsNetwork
    };

    await _repository.AddAsync(entity, cancellationToken);

    await _repository.SaveChangesAsync(cancellationToken);

    await _repository.CommitAsync(cancellationToken);

    var dto = new RegistryDTO(entity.Id, entity.FirstName, entity.LastName, entity.CompanyName, entity.LegalName, entity.Denomination, entity.IsPerson, entity.IsCompany, entity.IsCustomer, entity.IsSupplier, entity.IsNetwork);
    await _mediatR.Publish(new AddedRegistryDomainEvent() { Id = dto.Id.Value, Denomination = dto.Denomination }, CancellationToken.None);

    return dto;
}

And this is my event handler

public class AddedRegistryEventHandler : INotificationHandler<AddedRegistryDomainEvent>
{
    public async Task Handle(AddedRegistryDomainEvent notification, CancellationToken cancellationToken)
    {
        _log.LogInformation("This is the domain event with GUID: {EventId}", notification.EventId);
        _log.LogInformation("Registry entity successfully added with Id: {Id}", notification.Id);
        var @event = new AddedRegistryIntegrationEvent()
        {
            Id = notification.Id,
            Denomination = notification.Denomination
        };
        await _bus.Send(@event, cancellationToken);
    }
}

When i go to breakpoint inside it is never hit and it actually never logs anything from inside the eventhandler the only log i get is when it sends the command to add a Registry