CQRS & PurchaseOrder AggregateRoot

我是CQRS和DDD的新手，为了练习，我正在使用MS WideWorldImporters数据库，目前我被困在采购订单下达命令上，说实话我不知道它应该是什么样子，你能指导我吗？ 我应该有 1 个 PlaceOrderCommand 和处理程序应该使用它来创建采购订单填写其订单行并保存。如果是，当域模型如下所示时，命令应如下所示：

示例域模型：

public class PurchaseOrder : AggregateRoot<int>
{
    private PurchaseOrder(int id, int supplierID, DateTime orderDate, int deliveryMethodID, int contactPersonID) : base(id)
    {
        SupplierID = supplierID;
        OrderDate = orderDate;
        DeliveryMethodID = deliveryMethodID;
        ContactPersonID = contactPersonID;
    }
    public List<PurchaseOrderLine> PurchaseOrderLines { get; private set; }
    public int SupplierID { get; private set; }
    public DateTime OrderDate { get; private set; }
    public int DeliveryMethodID { get; private set; }
    public int ContactPersonID { get; private set; }
    public static PurchaseOrder CreatePurchaseOrder(int supplierID, int deliveryMethodID, int contactPersonID)
    {
        return new PurchaseOrder(1, supplierID, DateTime.Now, deliveryMethodID, contactPersonID);
    }
    public void AddPurchaseOrderLine(int stockItemID)
    {
        PurchaseOrderLines.Add(new PurchaseOrderLine(this.Id, stockItemID));
    }
}

示例命令处理程序：

    public class PurchaseOrdersCommandHandler : 
    ICommandHandler<PlacePurchaseOrder>
{
    private readonly IPurchaseOrderRepository purchaseOrderRepository;
    public PurchaseOrdersCommandHandler(IPurchaseOrderRepository purchaseOrderRepository)
    {
        this.purchaseOrderRepository = purchaseOrderRepository;
    }
    public void Handle(PlacePurchaseOrder command)
    {
        // TODO: based on command Create Purchase order with its line items and save it to db as a whole
    }
}

public void Handle(PlacePurchaseOrder command)
{
    var purchaseOrder = PurchaseOrder.CreatePurchaseOrder(command.id, command.upplierID, command.orderDate, command.deliveryMethodID, command.contactPersonID);
    foreach(int stockItemID in command.OrderLines)
    {
        purchaseOrder.AddPurchaseOrderLine(stockItemID)
    }
    this.purchaseOrderRepository.Save(purchaseOrder);
}