Aggregate with injected dependency

[fbjerggaard]

I want to inject a service in my Aggregate to be able to do some work before/after applying the changes and stumbled upon the example on how to register an aggregate with dependencies:

builder.Services.AddAggregate<Payment>(
    sp => new Payment(sp.GetRequiredService<PaymentProcessor>, otherService)
);

So far so good.

Now my aggregate looks like the following:

public class Payment: Aggregate<PaymentState>
{
    private readonly PaymentProcessor _processor;

    public Shipment(PaymentProcessor processor)
    {
        _processor = processor;
    }
}

All good so far.

Add a parameterless constructor to the Payment aggregate - since otherwise the CommandService complains:
'Payment' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'TAggregate' in the generic class 'Eventuous.CommandService<TAggregate,TState,TId>'

And then. It doesn't work. My PaymentProcessor is null since it is being loaded throgh the parameterless constructor.

I can get it to load something in the constructor with the PaymentProcessor parameter (setting a breakpoint in both constructors), but I am not really sure why one is used over the other.

Another side-issue is that an aggregate is registered as a singleton by default while I need them as scoped - but that's a topic for when I get the default implementation to work :)

[alexeyzimarev]

Have you added app.UseAggregateFactory();?

Regarding scoped registrations, Eventuous currently doesn't properly support it. I can't say how much work it would be to add request scopes to the service tbh, but, yes, it might be worth doing.

[fbjerggaard]

Yes I have added app.UseAggregateFactory();

I think making the scope user-configurable is a good idea, or at least making them scoped by default. I can see a lot of use cases for scoped services - at least in my case.

But that's probably a seperate discussion