Skip to main content

IPipelineBehavior

Namespace: RA.Utilities.Dispatcher.Abstractions

IPipelineBehavior<TRequest> and IPipelineBehavior<TRequest, TResponse> let you inject cross-cutting concerns around request handler execution — validation, logging, transaction management, caching — without touching the handlers themselves.

📦 Type Definition​

public interface IPipelineBehavior<TRequest> where TRequest : IRequest
{
    ValueTask<Result> HandleAsync(TRequest request, RequestHandlerDelegate next, CancellationToken cancellationToken);

    ValueTask<Result> HandleAsync<TContext>(
        TRequest request, RequestHandlerContextDelegate<TContext> next,
        PipelineContext<TContext> context, CancellationToken cancellationToken)
        where TContext : class, new()
        => HandleAsync(request, () => next(context), cancellationToken); // default implementation
}

public interface IPipelineBehavior<TRequest, TResponse> where TRequest : IRequest<TResponse>
{
    ValueTask<Result<TResponse>> HandleAsync(TRequest request, RequestHandlerDelegate<TResponse> next, CancellationToken cancellationToken);

    ValueTask<Result<TResponse>> HandleAsync<TContext>(
        TRequest request, RequestHandlerContextDelegate<TResponse, TContext> next,
        PipelineContext<TContext> context, CancellationToken cancellationToken)
        where TContext : class, new()
        => HandleAsync(request, () => next(context), cancellationToken); // default implementation
}

🎯 How It Works​

Behaviors form a chain around the handler. The dispatcher composes them in registration order, outermost first; the next delegate you receive invokes the next behavior — or the handler itself when you're innermost.

A behavior can:

  • Do work before and after — e.g., start a stopwatch, await next(), then log the elapsed time.
  • Short-circuit — return a failed Result without calling next() (that's exactly what ValidationBehavior does on invalid requests).
  • Transform — inspect or replace the Result returned by the inner pipeline.

🚀 Custom Behavior Example​

public class TimingBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
    where TRequest : IRequest<TResponse>
{
    public async ValueTask<Result<TResponse>> HandleAsync(
        TRequest request, RequestHandlerDelegate<TResponse> next, CancellationToken cancellationToken)
    {
        var stopwatch = Stopwatch.StartNew();
        Result<TResponse> result = await next();
        Console.WriteLine($"Handled in {stopwatch.ElapsedMilliseconds} ms");
        return result;
    }
}

🔧 Registration​

Closed (non-generic) behaviors are auto-registered by the source generator under their interface. Generic behaviors (like the one above) must be registered explicitly:

builder.Services
    .AddDispatcher<MyCommand, int, MyCommandHandler>()
    .AddDecoration<TimingBehavior<MyCommand, int>>();

See Auto Registration for the discovery rules and the DSAG010 diagnostic.

🔗 Related​