ProcessingPipeline.cs

public class MediatorPipeline<TRequest, TResponse> 
  : IRequestHandler<TRequest, TResponse>
  where TRequest : IRequest<TResponse>
{
    private readonly IRequestHandler<TRequest, TResponse> _inner;
    private readonly IEnumearble<IMessageValidator<TRequest>> _validators;
    private readonly IMessageAuthorizer _authorizer;
    private readonly IEnumerable<IPreRequestProcessor<TRequest>> _preProcessors;
    private readonly IEnumerable<IPostRequestProcessor<TRequest, TResponse>> _postProcessors;
    private readonly IEnumerable<IResponseProcessor<TResponse>> _responseProcessors;

    public MediatorPipeline(IRequestHandler<TRequest, TResponse> inner,
        IEnumerable<IMessageValidator<TRequest>> validator,
        IMessageAuthorizor authorizer,
        IEnumerable<IPreRequestProcessor<TRequest>> preProcessors,
        IEnumerable<IPostRequestProcessor<TRequest, TResponse>> postProcessors,
        IEnumerable<IResponseProcessor<TResponse>> responseProcessors
        )
    {
        _inner = inner;
        _validators = validators;
        _authorizer = authorizer;
        _preProcessors = preProcessors;
        _postProcessors = postProcessors;
        _responseProcessors = responseProcessors;
    }

    public TResponse Handle(TRequest message)
    {
        using (LogContext.PushProperty(LogConstants.MediatRRequestType, requestType))
        using (Metrics.Time(Timers.MediatRRequest))
        {
            _securityHandler.Evaluate(message);
            
            foreach (var preProcessor in _preProcessors)
                preProcessor.Handle(request);
            
            var failures = _validators
                .Select(v => v.Validate(message))
                .SelectMany(result => result.Errors)
                .Where(f => f != null)
                .ToList();
            if (failures.Any())
                throw new ValidationException(failures);
            
            var response = _inner.Handle(request);
            
            foreach (var postProcessor in _postProcessors)
                postProcessor.Handle(request, response);
                
            foreach (var responseProcessor in _responseProcessors)
                responseProcessor.Handle(response);
                
            return response;
        }
    }
 }