MediatR и pipeline в слое Application — Pipeline behaviours

public class ValidationBehaviour<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
    where TRequest : notnull
{
    private readonly IEnumerable<IValidator<TRequest>> _validators;

    public async Task<TResponse> Handle(
        TRequest request,
        RequestHandlerDelegate<TResponse> next,
        CancellationToken cancellationToken)
    {
        if (_validators.Any())
        {
            var context = new ValidationContext<TRequest>(request);
            var results = await Task.WhenAll(
                _validators.Select(v => v.ValidateAsync(context, cancellationToken)));
            var failures = results.SelectMany(r => r.Errors).Where(f => f != null).ToList();
            if (failures.Count != 0)
                throw new ValidationException(failures);
        }
        return await next();
    }
}