null.cs

public class GetOrderQueryHandler : IRequestHandler<GetOrderQuery, OrderResponse>
{
    private readonly IOrderReadService _orderReadService;

    public GetOrderQueryHandler(IOrderReadService orderReadService)
    {
        _orderReadService = orderReadService;
    }
    
    public async Task<OrderResponse> Handle(GetOrderQuery request, CancellationToken cancellationToken)
    {
        var orderResponse = await _orderReadService.GetOrderByIdAsync(request.OrderId);

        if (orderResponse is null)
        {
            throw new OrderNotFoundException(request.OrderId);
        }

        return orderResponse;
    }
}