Order.cs

public class FulfillOrder
{
    private readonly IOrderRepository _repository;
    private readonly IMapper _mapper;

    public FulfillOrder(IOrderRepository repository, IMapper mapper)
    {
        _repository = repository;
        _mapper = mapper;
    }
    
    public async Task Handle(int orderId)
    {
        var entity = await _repository.GetById(orderId);
        var domain = _mapper.Map<Order>(entity);
        domain.Fulfill();
        await _repository.Update(_mapper.Map<OrderEntity>(domain));
    }
}