违反多重约束 - 实体框架

Question

我在尝试保存一些数据时遇到问题。我想要做的是，我有订单，我有一份已经履行并付款的订单。但是，订单类型错误且需要更改，但这样做可能意味着增值税无法添加到订单中，因此需要计算调整以向客户提供资金或让客户付款。所以我的想法是，当在现有的付费订单上更改订单类型时，我创建订单的副本，因此SQL数据库中的另一行（订单表）具有相同的详细信息，创建项目（项目表）的副本在订单中。但是，订单表中的订单类型将有所不同。但是，当我尝试这样做时，我收到了错误

  

多重约束违反了角色＆＃39; _关系的目标有多重性1或0..1

用户在屏幕上打开订单，从会话中检索订单详细信息并存储......

public void Save()
{
    App_Order form;
    List<App_Items> itemsInSession;
    ...
    try
    {
        form = (App_Order)Session["Form" + id];
        itemsInSession = (List<App_Items>)Session["FormDrugItems" + id];        
    }

    // some validation is done

    if(orderTypeChanged == true)
    {
        App_Order duplicateOrder = new App_Order();
        duplicateOrder = CreateDuplicateOrderForm(form);
        _orderService.SaveForm(duplicateOrder);
    }

}

...

public App_Order CreateDuplicateOrderForm(App_Order form)
{
    App_Order newForm = new App_Order()
    {
        OrderType = form.orderType,
        OrderDate = form.orderDate,
        CustomerId = form.customerId,
    }

    newForm.App_Items = new List<App_Items>();

    foreach(App_Items orderItem in form.App_Item)
    {
        App_Items item = new App_Items()
        {
            ItemCode = orderItem.itemCode,
            Quantity = orderItem.quantity,
            Cost = orderItem.cost
        };

        newForm.App_Items.Add(item);
    }
}

Multiplicity Constraint Violation提到App_Customer具有多重性。它将是来自App_Customer的CustomerId，它存储在CustomerId列的App_Order表中。

关于我做错了什么或我能做些什么来修复它的任何建议？

提前致谢：）

App_Order：

public partial class App_Order
{
    [ExcludeFromCodeCoverage]
    public App_Order()
    {
        this.App_PharmacyFormDrugItem = new HashSet<App_PharmacyFormDrugItem>();
    }

    public int OrderId { get; set; }
    public short OrderTypeId { get; set; }
    public short OrderDate { get; set; }

    public int CustomerId { get; set; }
    public Nullable<int> CustomerId_Initial { get; set; }


    public virtual Ref_OrderType Ref_OrderType { get; set; }
    public virtual Ref_PaymentMonth Ref_PaymentMonth { get; set; }

    public virtual App_Customer App_Customer { get; set; }
    public virtual App_Customer App_Customer_Initial { get; set; }

    public virtual ICollection<App_Item> App_Item { get; set; }

}

App_Customer：

public partial class App_Contract
{
    public App_Contract()
    {
        this.App_CustomerAddress = new HashSet<App_CustomerAddress>();
        this.App_CustomerContact = new HashSet<App_CustomerContact>();
    }

    public int CustomerId { get; set; }
    public short CustomerTypeId { get; set; }
    public short CustomerSubTypeId { get; set; }
    public string Name { get; set; }


    public virtual ICollection<App_CustomerAddress> App_CustomerAddress { get; set; }
    public virtual ICollection<App_CustomerContact> App_CustomerContact{ get; set; }

    public virtual Ref_CustomertSubType Ref_CustomerSubType { get; set; }
    public virtual Ref_CustomerType Ref_CustomerType { get; set; }

    public virtual ICollection<App_Order> App_Order{ get; set; }

    public virtual ICollection<App_Order> App_Order1 { get; set; }

    public virtual ICollection<App_Order> App_Order2 { get; set; }

}