c# – EntityFramework 4.0 POCO代理问题

2023年8月4日 110次阅读

我看到很多人都在问一个类似的问题,但不是这个问题.我正在尝试用POCO代理做我希望相对简单的事情.

using (var context = new MyObjectContext())
{
    context.ContextOptions.ProxyCreationEnabled = true;

    // this does indeed create an instance of a proxy for me...
    // something like Product_SomeBunchOfNumbersForProxy
    var newEntity = context.CreateObject<MyEntity>();

    // throws exception because newEntity is not in ObjectStateManager...why??
    context.ObjectStateManager.GetObjectStateEntry(newEntity);

    // ok, well I guess let's add it to the context manually...
    context.AddObject("Model.Products", newEntity);

    // doesn't throw an exception...I guess that's good
    var state = context.ObjectStateManager.GetObjectStateEntry(newEntity); 

    // prints System.Data.EntityState.Unchanged...oh...well that's not good
    Console.WriteLine(state.State);

    // let's try this...
    context.DetectChanges();

    // doesn't throw an exception...I guess that's good
    state = context.ObjectStateManager.GetObjectStateEntry(newEntity);

    // prints System.Data.EntityState.Unchanged...still no good...
    Console.WriteLine(state.State);

    // dunno, worth a shot...
    context.Refresh(RefreshMode.ClientWins);

    // throws exception because newEntity is not in ObjectStateManager...
    // that didn't help...
    state = context.ObjectStateManager.GetObjectStateEntry(newEntity);
}

我究竟做错了什么？谢谢！

最佳答案 我没有对代理做太多,但看起来你期望它跟踪一个没有持久状态的对象的变化.

CreateEntity实际上只是创建了对象.这与说“新MyEntity”没什么不同.因此,您必须将该实体添加到上下文并保存更改,然后才能跟踪以下任何真正的“状态”：

using (var context = new MyObjectContext())
{
    context.ContextOptions.ProxyCreationEnabled = true;
    var newEntity = context.CreateObject<MyEntity>();
    context.Add(newEntity);
    context.SaveChanges();
    // now GetObjectStateEntry(newEntity) should work just fine.
    // ...
}
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