public void Handle(RegisterAnnotationCommand message)
        {
            var annotation = new Annotation(message.Title, message.Description);

            if (!AnnotationValid(annotation.AnnotationHistory.FirstOrDefault()))
            {
                return;
            }

            _annotationRepository.Add(annotation);

            if (Commit())
            {
                _bus.RaiseEvent(new AnnotationRegistredEvent(annotation.Id));
            }
        }
        public Task <Unit> Handle(RegisterAnnotationCommand request, CancellationToken cancellationToken)
        {
            var annotation = new Annotation(request.Title, request.Description);

            if (!AnnotationValid(annotation.AnnotationHistory.FirstOrDefault()))
            {
                return(Unit.Task);
            }

            _annotationRepository.Add(annotation);

            if (Commit())
            {
                _mediator.RaiseEvent(new AnnotationRegistredEvent(annotation.Id));
            }
            return(Unit.Task);
        }