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INotificationHandler

Namespace: RA.Utilities.Dispatcher.Abstractions

INotificationHandler<TNotification> is the interface your notification subscribers implement. Each notification can have any number of handlers; Publish runs all of them, each wrapped in its own behavior pipeline.

📦 Type Definition​

public interface INotificationHandler<in TNotification> where TNotification : INotification
{
    ValueTask<Result> HandleAsync(TNotification notification, CancellationToken cancellationToken);

    ValueTask<Result> HandleAsync<TContext>(
        TNotification notification, PipelineContext<TContext> context, CancellationToken cancellationToken)
        where TContext : class, new()
        => HandleAsync(notification, cancellationToken); // default implementation
}

🎯 Purpose​

Notification handlers perform side effects in response to events: send emails, update caches, write audit logs. Each handler:

  • Returns Result.Success() on success, Result.Failure(exception) on expected failure.
  • Is invoked independently — a failure in one handler never prevents the others from running. Publish aggregates the failures into its returned Result.
  • Gets its own notification behavior pipeline (retry, logging, metrics) when behaviors are registered.

🚀 Usage​

using RA.Utilities.Core.Results;
using RA.Utilities.Dispatcher.Abstractions;

public class SendConfirmationEmail : INotificationHandler<OrderPlaced>
{
    private readonly IEmailService _emailService;

    public SendConfirmationEmail(IEmailService emailService) => _emailService = emailService;

    public async ValueTask<Result> HandleAsync(OrderPlaced notification, CancellationToken cancellationToken)
    {
        await _emailService.SendAsync(notification.CustomerEmail, "Order Confirmed");
        return Result.Success();
    }
}

🔧 Auto-Registration​

Concrete, non-generic INotificationHandler<TNotification> implementations are discovered by the package's source generator and registered automatically when AddMediator() is called (transient) — no explicit AddNotification().AddHandler<>() needed for plain handlers.

🔗 Related​