Duplicated metadata key when implementing IMetadataProvider

[foliv57]

Hi,

I'm trying to play around with IMetadataProvider. My ultimate goal is to create a provider that injects a "saga-id" to the metadata by extracting it from aggregate event (if this event implements a specific ISagaEvent).
It's not a super design, but it was more to test the IMetadataProvider and to have a workaround for my ISagaLocator.

My problem is that my IMetadataProvider is triggered multiple time for the same event and ends by throwing a "An item with the same key has already been added. Key: saga-id" error.

The implementation of my IMetadataProvider is:

public class SagaIdMetadataProvider : IMetadataProvider
{
    public IEnumerable<KeyValuePair<string, string>> ProvideMetadata<TAggregate, TIdentity>(TIdentity id, IAggregateEvent aggregateEvent, IMetadata metadata)
        where TAggregate : IAggregateRoot<TIdentity>
        where TIdentity : IIdentity
    {
        if (!metadata.ContainsKey("saga-id") && aggregateEvent is ISagaEvent sagaEvent)
        {
            yield return new KeyValuePair<string, string>("saga-id", sagaEvent.GetSagaId().Value);
        }
    }
}

And I register it like this:

builder.Services.AddEventFlow(ef =>
{
    ef.AddDefaults(typeof(Application).Assembly);
    ef.AddMetadataProvider<SagaIdMetadataProvider>();
});

My event is only instantiated and emitted ones like this:

public IExecutionResult PlaceOrder(int numberOfPersons)
{
    Emit(new OrderPlaced(this.Id, numberOfPersons));
    return ExecutionResult.Success();
}

This event is the event that starts the Saga with the implementation of ISagaIsStartedBy<Order, OrderId, OrderPlaced>.

Thanks for your help.

Dotnet version: 8.0
EventFlow version: 1.2.2

[foliv57]

Hi,

I found my error. It seems that ef.AddDefaults(typeof(Application).Assembly); already register automatically all IMetadataProvider implementations.

Meaning that by adding ef.AddMetadataProvider<SagaIdMetadataProvider>();, I registered it twice.