无法在EF4中添加具有现有子实体的父实体

Question

我正在使用一个通用存储库作为我的存储库中的DataLayer。现在，我正在创建一个新的实体(Order)，并根据用户选择的值向其添加OrderDetail。

每个OrderDetail有一个->，一个与Product的关系。用户选择一个产品，我将其添加到OrderDetail中，然后添加到订单中。

现在，Order和OrderDetail是“新”对象，但是产品(及其相关实体)从我的数据库中检索并添加到OrderItem (当时只有一个)。因此，它们被附加到一个DynamicProxy (我的上下文是由泛型存储库创建的)

我总是得到IEntityChangeTracker的错误：

实体对象不能由多个IEntityChangeTracker实例引用

现在，我知道问题在于DbContext ...but，我仍然无法找到任何解决方案，有什么想法吗？

这是我的DbContext课

/这是数据访问层管理类。/公共部分类MyDataLayer {/这是我们将该类的实例存储在。/在属性中使用。/私有静态只读字符串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

添加图表时，EF将更改实体的状态，即使它们已经被跟踪。我相信在您的情况下，因为您添加了一个实体，相关实体的状态(在上下文中已经被跟踪)将更改为add。您可以做的是首先添加新实体，并在添加实体后设置关系。