[英]Unable to add parent entity with existing child entities in EF4
我正在使用通用存储库作为存储库中的DataLayer。 现在,我将创建一个新实体(订单),并根据用户选择的值向其添加OrderDetail。
每个OrderDetail与Product都有一个->一个关系。 用户选择一种产品,然后将其添加到已添加到订单中的OrderDetail中。
现在,Order和OrderDetail是“新”对象,但是Product(及其相关实体)从我的数据库中检索并添加到OrderItem(当时是一个)中。 因此,它们被附加到DynamicProxy(我的上下文是由通用存储库创建的)
我总是收到IEntityChangeTracker的错误:
实体对象不能由IEntityChangeTracker的多个实例引用
现在,我知道问题出在DbContext上...但是仍然我找不到任何解决方案,任何想法?
这是我的DbContext类
/// ///这是数据访问层管理类。 ////公共局部类MyDataLayer {/// ///这是将此类的实例存储在中的键。 ///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;
}
}
}
当您添加图时,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,所以相关实体的状态(在上下文中已被跟踪)将变为添加。 您可以做的是先添加新实体,然后在添加实体后设置关系。
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