PlaceOrderDelegate.cs

public class PlaceOrderHandler : IHandleMessages<PlaceOrder>
{
    private readonly SalesDbContext _dbContext;
    private readonly WarehouseInventoryQuery.DoAllProductsHaveQtyOnHand _doAllProductsHaveQtyOnHand;

    public PlaceOrderHandler(SalesDbContext dbContext, WarehouseInventoryQuery.DoAllProductsHaveQtyOnHand doAllProductsHaveQtyOnHand)
    {
        _dbContext = dbContext;
        _doAllProductsHaveQtyOnHand = doAllProductsHaveQtyOnHand;
    }

    public async Task Handle(PlaceOrder message, IMessageHandlerContext context)
    {
        if (_doAllProductsHaveQtyOnHand(message.OrderId) == false)
        {
            return;
        }

        await _dbContext.Orders.AddAsync(new Order
        {
            OrderId = message.OrderId,
            Status = OrderStatus.Pending
        });
        await _dbContext.SaveChangesAsync();

        var orderPlaced = new OrderPlaced
        {
            OrderId = message.OrderId
        };
        await context.Publish(orderPlaced);
    }
}