PipelineBehaviour for all Requests

Hi,

i’m new to MediatR and i tried to create a validation behavior for all my requests (commands and queries). But the example i’ve found works for queries only. So the question is, do i have to implement all behaviours twice?

public class ValidationBehaviour<TRequest, TResponse> : IPipelineBehaviour<TRequest, TResponse> where TRequest : IRequest<TResponse>
    {
        private readonly IEnumerable<IValidator<TRequest>> validators;

        public ValidationBehaviour( IEnumerable<IValidator<TRequest>> validators )
        {
            if (validators == null)
            {
                throw new ArgumentNullException(nameof(validators));
            }

            this.validators = validators;
        }

        public Task<TResponse> Handle( TRequest request, RequestHandlerDelegate<TResponse> next )
        {
            var context = new ValidationContext( request );

            var failures = this.validators.Select( v => v.Validate( context ) ).SelectMany( result => result.Errors ).Where( f => f != null ).ToList();

            if( failures.Any() )
            {
                throw new ValidationException( failures );
            }

            return next();
        }
    }

[jbogard]

The wiki is open for anyone to contribute.

[endeffects]

Thanks for your help. I got it working now with the PreRequestProcessor. I found out that i forgot to register the RequestPreProcessorBehaviour. Now everything is working as expected.

I have to say that i really like your MediatR library, but it is really hard to find some documentation and examples beyond the standard. Maybe you can improve this in the future. 😃