Filtro de Notificaciones

INotificationFilter<TNotification> permite que un handler omita condicionalmente su propia ejecución según los datos de la notificación.

Interfaz

public interface INotificationFilter<TNotification> where TNotification : INotification
{
    bool ShouldHandle(TNotification notification, CancellationToken ct);
}

Uso

public class PremiumCustomerEmailHandler
    : INotificationHandler<OrderPlacedEvent>,
      INotificationFilter<OrderPlacedEvent>
{
    private readonly ICustomerService _customerService;

    public PremiumCustomerEmailHandler(ICustomerService customerService)
    {
        _customerService = customerService;
    }

    // Filtro: solo manejar eventos de clientes premium
    public bool ShouldHandle(OrderPlacedEvent notification, CancellationToken ct)
    {
        return _customerService.IsPremium(notification.CustomerId);
    }

    public async Task Handle(OrderPlacedEvent notification, CancellationToken ct)
    {
        await _emailService.SendPremiumOrderConfirmationAsync(
            notification.CustomerId,
            notification.OrderId);
    }
}

Comportamiento

• Cuando ShouldHandle retorna false, el handler se omite silenciosamente — no se lanza ninguna excepción
• Cuando ShouldHandle retorna true, el handler se ejecuta normalmente
• Los demás handlers no se ven afectados

Ejemplo: Flag de Característica

public class BetaFeatureNotificationHandler
    : INotificationHandler<UserRegisteredEvent>,
      INotificationFilter<UserRegisteredEvent>
{
    private readonly IFeatureFlags _featureFlags;

    public BetaFeatureNotificationHandler(IFeatureFlags featureFlags)
    {
        _featureFlags = featureFlags;
    }

    public bool ShouldHandle(UserRegisteredEvent notification, CancellationToken ct)
    {
        return _featureFlags.IsEnabled("BetaWelcomeEmail");
    }

    public async Task Handle(UserRegisteredEvent notification, CancellationToken ct)
    {
        await _emailService.SendBetaWelcomeEmailAsync(notification.UserId);
    }
}