無法在EF4中將父實體與現有子實體一起添加

Question

我正在使用通用存儲庫作為存儲庫中的DataLayer。 現在，我將創建一個新實體（訂單），並根據用戶選擇的值向其添加OrderDetail。

每個OrderDetail與Product都有一個->一個關系。 用戶選擇一種產品，然后將其添加到已添加到訂單中的OrderDetail中。

現在，Order和OrderDetail是“新”對象，但是Product（及其相關實體）從我的數據庫中檢索並添加到OrderItem（當時是一個）中。 因此，它們被附加到DynamicProxy（我的上下文是由通用存儲庫創建的）

我總是收到IEntityChangeTracker的錯誤：

實體對象不能由IEntityChangeTracker的多個實例引用

現在，我知道問題出在DbContext上...但是仍然我找不到任何解決方案，任何想法？

這是我的DbContext類

/// ///這是數據訪問層管理類。 ////公共局部類MyDataLayer {/// ///這是將此類的實例存儲在中的鍵。 ///在屬性中使用。 ///私有靜態只讀字符串UOW_INSTANCE_KEY =“ MyDataLayer_Instance”;

    /// <summary>
    /// This is used for thread-safety when creating the instance of this class to be stored in
    /// the UnitOfWorkStore.
    /// </summary>
    private static readonly object s_objSync = new object();

    // The DataContext object
    private readonly ITTEntities m_context;



    // ********************************************************************************
    // *** Constructor(s) *************************************************************
    // ********************************************************************************

    /// <summary>
    /// Default constructor.  Creates a new MyEntities DataContext object.
    /// This is hidden (private) because the instance creation is managed as a "unit-of-work", via the
    /// <see cref="Instance" /> property.
    /// </summary>
    private MyDataLayer()
    {
        m_context = new ITTEntities();
    }



    // ********************************************************************************
    // *** Public properties **********************************************************
    // ********************************************************************************

    /// <summary>
    /// The ObjectContext object that gives us access to our business entities.
    /// Note that this is NOT static.
    /// </summary>
    public ITTEntities Context
    {
        get { return m_context; }
    }


    /// <summary>
    /// This will get the "one-and-only" instance of the MyDataLayer that exists for the lifetime of the current "unit of work",
    /// which might be the lifetime of the currently running console application, a Request/Response iteration of an asp.net web app,
    /// an async postback to a web service, etc.
    /// 
    /// This will never return null.  If an instance hasn't been created yet, accessing this property will create one (thread-safe).
    /// This uses the <see cref="UnitOfWorkStore" /> class to store the "one-and-only" instance.
    /// 
    /// This is the instance that is used by all of the DAL's partial entity classes, when they need a reference to a MyEntities context
    /// (MyDataLayer.Instance.Context).
    /// </summary>
    public static MyDataLayer Instance
    {
        get
        {
            object instance = UnitOfWorkStore.GetData(UOW_INSTANCE_KEY);

            // Dirty, non-thread safe check
            if (instance == null)
            {
                lock (s_objSync)
                {
                    // Thread-safe check, now that we're locked
                    if (instance == null) // Ignore resharper warning that "expression is always true".  It's not considering thread-safety.
                    {
                        // Create a new instance of the MyDataLayer management class, and store it in the UnitOfWorkStore,
                        // using the string literal key defined in this class.
                        instance = new MyDataLayer();
                        UnitOfWorkStore.SetData(UOW_INSTANCE_KEY, instance);
                    }
                }
            }

            return (MyDataLayer)instance;
        }
    }
}

Answer 1

當您添加圖時，EF將更改實體的狀態，即使它們已經被跟蹤。 我相信在您的情況下，因為您添加了一個實體，所以相關實體的狀態（在上下文中已被跟蹤）將變為添加。 您可以做的是先添加新實體，然后在添加實體后設置關系。