NHibernate，代理和平等 [英] NHibernate, proxies and equality

问题描述

我正在使用NHibernate 3.3.1，发现了一个非常有趣的问题. 在我的域模型中，我定义了两个类:Carriage和CarriageRequest，它们相互引用.因为延迟加载已打开，所以当我访问carry.CarriageRequest时，它指向一个代理对象.好的，可以.但是，当我调用CarriageRequest类中定义的任何方法时，"this"将引用第三个对象实例.

I'm using NHibernate 3.3.1 and found very interesting problem. In my domain model I defined two classes: Carriage and CarriageRequest, referencing each other. Because lazy loading is turned on, when I access carriage.CarriageRequest - it points to a proxy object. That is okay. But when I invoke any method, defined in CarriageRequest class, 'this' references to a third object instance.

示例:

class CarriageRequest
{
  public virtual void Test(CarriageRequest instance)
  {
    Debug.WriteLine(Object.ReferenceEquals(this, instance)); // prints FALSE
  }
}

class Carriage
{ 
  public virtual CarriageRequest CarriageRequest { get; set; }
}

...
var carriage = session.Get<Carriage>(123);
carriage.CarriageRequest.Test(carriage.CarriageRequest);

因此，看起来NHibernate代理包装原始对象并将所有方法调用转发到包装对象.在这种情况下，如何使用"=="? 我需要做这样的事情:

So it looks like NHibernate proxies wrap original objects and forward all method invocations to wrapped objects. How can I use "==" in this case? I need to do something like this:

var shipment = (from sh in Carriage.Shipments where sh.CarriageRequest == this & sh.Warehouse == waybill.Warehouse select sh).FirstOrDefault();

此代码在代理对象内内部执行，所以'shipment'始终为null，因为'sh.CarriageRequest == this'始终为false.因为sh.CarriageRequest是代理，而这是一个包装好的原始实例.

This code is executed inside proxied object, so 'shipment' is always null, because 'sh.CarriageRequest == this' is always false. Because sh.CarriageRequest is a proxy, and this is a wrapped original instance.

推荐答案

好吧，NHibernate保证同一会话中已加载对象的引用相等.而且，如果使用延迟加载，它将使用代理包装实际对象，并且代理上的每个方法调用都将转发到包装的对象.因此，在此对象内，"this"与从会话加载的同一对象之间的每个引用比较都将失败(因为它将是一个不同的代理对象).

Okay, NHibernate guarantees reference equality for loaded objects within the same session. And if using lazy-loading, it wraps real object with a proxy and every method invocation on a proxy is forwarded to the wrapped object. So, inside this object every reference comparison between 'this' and the same object, loaded from session, will fail (because it will be a different, proxy, object).

因此，解决此问题的唯一方法是使用Equals方法或通过主键进行比较.

So, the only way to resolve this issue is to use Equals method or compare by primary keys.

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