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IRequestHandler

Namespace: RA.Utilities.Dispatcher.Abstractions

IRequestHandler<TRequest> and IRequestHandler<TRequest, TResponse> are the interfaces your request handlers implement. They define a single abstract member, HandleAsync, plus a context-aware overload with a default implementation.

📦 Type Definition​

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

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

public interface IRequestHandler<in TRequest> where TRequest : IRequest
{
    ValueTask<Result> HandleAsync(TRequest request, CancellationToken cancellationToken);

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

🎯 Purpose​

Handlers contain your business logic. They return results:

  • Success — Result.Success(value) / Result.Success().
  • Expected failure — Result.Failure(exception) with a typed exception from RA.Utilities.Core.Exceptions (NotFoundException, ConflictException, BadRequestException, ...). Failures are returned, not thrown — truly exceptional cases still throw.

🚀 Usage​

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

public class CreateProductHandler : IRequestHandler<CreateProductCommand, int>
{
    public async ValueTask<Result<int>> HandleAsync(
        CreateProductCommand command, CancellationToken cancellationToken)
    {
        if (await _repository.DoesProductExistAsync(command.Name, cancellationToken))
            return Result.Failure<int>(new ConflictException(nameof(Product), command.Name));

        return Result.Success(await _repository.AddAsync(command, cancellationToken));
    }
}

🔧 Auto-Registration​

Concrete, non-generic IRequestHandler implementations are discovered by the package's source generator and registered automatically when AddMediator() is called (request handlers scoped) — no explicit AddDispatcher call needed. See the Auto Registration guide for the discovery rules and diagnostics.

🔗 Related​