public void Handle(UpdateAnnotationCommand message)
        {
            if (!AnnotationExisting(message.AggregateId, message.MessageType))
            {
                return;
            }

            var history = new AnnotationHistory(message.Title, message.Description, message.AggregateId);

            if (!AnnotationValid(history))
            {
                return;
            }

            _annotationRepository.AddHistory(history);

            if (Commit())
            {
                _bus.RaiseEvent(new AnnotationUpdatedEvent(message.Title, message.Description, message.AggregateId));
            }
        }
        public Task <Unit> Handle(UpdateAnnotationCommand request, CancellationToken cancellationToken)
        {
            if (!AnnotationExisting(request.AggregateId, request.MessageType))
            {
                return(Unit.Task);
            }

            var history = new AnnotationHistory(request.Title, request.Description, request.AggregateId);

            if (!AnnotationValid(history))
            {
                return(Unit.Task);
            }

            _annotationRepository.AddHistory(history);

            if (Commit())
            {
                _mediator.RaiseEvent(new AnnotationUpdatedEvent(request.Title, request.Description, request.AggregateId));
            }
            return(Unit.Task);
        }