CommandHandlers.cs

    public class AddProductCommandHandler : IRequestHandler<AddProductCommand>
    {
        private readonly ProductDatabase _database;
        private readonly IMediator _mediator;

        public AddProductCommandHandler(ProductDatabase database, IMediator mediator)
        {
            _database = database;
            _mediator = mediator;
        }

        public void Handle(AddProductCommand command)
        {
            // command validation
            // add product to database
            
            var @event = new ProductAddedEvent(product.Id, product.Name, product.CategoryId);
            _mediator.Publish(@event);
        }
    }
    
    public class AddReviewCommandHandler : IRequestHandler<AddReviewCommand>
    {
        private readonly ProductDatabase _database;
        private readonly IMediator _mediator;

        public AddReviewCommandHandler(ProductDatabase database, IMediator mediator)
        {
            _database = database;
            _mediator = mediator;
        }

        public void Handle(AddReviewCommand command)
        {
            // command validation
            // add review to database

            var @event = new ReviewAddedEvent(review.Id, review.UserId, review.ProductId, review.Rating);
            _mediator.Publish(@event);
        }
    }
    
    public class CompleteOrderCommandHandler : IRequestHandler<CompleteOrderCommand>
    {
        private readonly ProductDatabase _database;
        private readonly IMediator _mediator;

        public CompleteOrderCommandHandler(ProductDatabase database, IMediator mediator)
        {
            _database = database;
            _mediator = mediator;
        }

        public void Handle(CompleteOrderCommand command)
        {
            // command validation
            // create order in database

            var @event = new OrderCompletedEvent(order.Id, order.ProductId, order.Amount);
            _mediator.Publish(@event);
        }
    }

    public class ChangeFieldValueCommandHandler
    {
        private readonly ProductDatabase _database;
        private readonly IMediator _mediator;

        public ChangeFieldValueCommandHandler(ProductDatabase database, IMediator mediator)
        {
            _database = database;
            _mediator = mediator;
        }

        public void Handle(ChangeFieldValueCommand command)
        {
            // command validation
            // change field value for product

            var @event = new FieldValueChangedEvent(fieldValue.Id, fieldValue.Value);
            _mediator.Publish(@event);
        }
    }