NHibernate Evict抛出未设置为对象错误实例的对象引用

Question

When I:

if (nhsession.Contains(myobj))
    nhsesion.Evict(myobj)

At the Evict method call I get this error:

{"Object reference not set to an instance of an object."}     ????????

With this stacktrace:

at NHibernate.Event.Default.EvictVisitor.EvictCollection(IPersistentCollection collection)
   at NHibernate.Event.Default.EvictVisitor.EvictCollection(Object value, CollectionType type)
   at NHibernate.Event.Default.EvictVisitor.ProcessCollection(Object collection, CollectionType type)
   at NHibernate.Event.Default.AbstractVisitor.ProcessValue(Object value, IType type)
   at NHibernate.Event.Default.AbstractVisitor.ProcessValue(Int32 i, Object[] values, IType[] types)
   at NHibernate.Event.Default.AbstractVisitor.ProcessEntityPropertyValues(Object[] values, IType[] types)
   at NHibernate.Event.Default.AbstractVisitor.Process(Object obj, IEntityPersister persister)
   at NHibernate.Event.Default.DefaultEvictEventListener.DoEvict(Object obj, EntityKey key, IEntityPersister persister, IEventSource session)
   at NHibernate.Event.Default.DefaultEvictEventListener.OnEvict(EvictEvent event)
   at NHibernate.Impl.SessionImpl.FireEvict(EvictEvent evictEvent)
   at NHibernate.Impl.SessionImpl.Evict(Object obj)
   at NewCash.UI.Presenters.OperazioneIRSPresenter.UserAction(String Action) in C:\AkrosProduzione\NewCash4\src_4\NewCash.UI\Presenters\OperazionePresenter\OperazioneIRSPresenter.vb:line 230

It seems that NHibernate evict tries to evict a null collection, how can I avoid this without having to initialize all collections properties of the object? Or is there a problem that I'm misunderstanding?

Answer 1

it looks like a bug as Rippo linked.

however even if it is a bug it is good practice to initialize collection properties to empty collections in the constructor of the model classes. Then it is not nessessary to check for null collection each time on access and to change the collection type (eg decorating it) there is only one place to change it.