Interface IAggregationService

Namespace

Stratara.Abstractions.EventSourcing

Assembly

Stratara.Abstractions.dll

Reconstructs an aggregate by reading its event stream + applying events. Command handlers and sagas use this — never read aggregates from projection views.

public interface IAggregationService

Extension Methods

AggregationServiceTenantExtensions.AggregateOwnedByTenantAsync<TAggregate>(IAggregationService, Guid, Guid, CancellationToken)

FieldChangedEventExtensions.ApplyPropertyChanged<TAggregate>(TAggregate, FieldChangedEvent<TAggregate>)

EventStream.ApplyEvents(object, IReadOnlyList<IEvent>)

Examples

Rehydrate an aggregate in a command handler, then apply a mutation:

public sealed class ShipOrderHandler(IAggregationService aggregator, IEventSource events)
    : ICommandHandler<ShipOrder>
{
    public async Task HandleAsync(ShipOrder command, CancellationToken cancellationToken)
    {
        var order = await aggregator.AggregateAsync<Order>(command.OrderId, cancellationToken: cancellationToken)
            ?? throw new InvalidOperationException($"Order {command.OrderId} not found.");

        await events.AppendAsync<Order>(order.Id, new OrderShipped(order.Id, DateTimeOffset.UtcNow),
            cancellationToken);
        await events.SaveChangesAsync(cancellationToken);
    }
}

Remarks

Tenant ownership: handlers operating on ITenantAggregates should prefer the AggregateOwnedByTenantAsync<TAggregate>(IAggregationService, Guid, Guid, CancellationToken) extension, which returns null on either "not found" or "wrong tenant" — the handler can then map both to NotFound without leaking foreign-tenant existence.

Methods

AggregateAsync(Type, Guid, long?, long?, CancellationToken)

Reflection-based variant for when the aggregate type is known only at runtime (replay tooling, generic admin endpoints).

Task<object?> AggregateAsync(Type aggregateType, Guid streamId, long? fromVersion = null, long? toVersion = null, CancellationToken cancellationToken = default)

Parameters

aggregateType Type

The aggregate type to construct.

streamId Guid

The aggregate's stream id.

fromVersion long?

Ignored. Rebuilding always starts from the beginning of the stream, or from the latest snapshot at or below toVersion, because an aggregate rebuilt from a later version alone would lack the state its earlier events established. Kept for source compatibility.

toVersion long?

Inclusive end version, or null for stream head.

cancellationToken CancellationToken

Propagated to the read-store query.

Returns

Task<object>

The reconstructed aggregate, or null if the stream does not exist.

AggregateAsync<TAggregate>(Guid, long?, long?, CancellationToken)

Reconstruct an aggregate of TAggregate from streamId's event stream.

Task<TAggregate?> AggregateAsync<TAggregate>(Guid streamId, long? fromVersion = null, long? toVersion = null, CancellationToken cancellationToken = default) where TAggregate : notnull, new()

Parameters

streamId Guid

The aggregate's stream id.

fromVersion long?

Ignored. Rebuilding always starts from the beginning of the stream, or from the latest snapshot at or below toVersion, because an aggregate rebuilt from a later version alone would lack the state its earlier events established. Kept for source compatibility.

toVersion long?

Inclusive end version, or null for stream head.

cancellationToken CancellationToken

Propagated to the read-store query.

Returns

Task<TAggregate>

The reconstructed aggregate, or null if the stream does not exist.

Type Parameters

TAggregate

The aggregate type — must have a parameterless constructor.