Question

My session uses an NHInterceptor to add INotifyPropertyChanged support to models.

// I use the session generated here to fetch Data
public class SessionServiceImpl : ISessionService
{
    [Inject]
    public ISessionFactory SessionFactory { get; set; }

    [Inject]
    public NhChangeNotificationInterceptorImpl ChangeNotificationInterceptor { get; set; }

    public ISession GetSession() // reduced code here
    {
        return SessionFactory.OpenSession(ChangeNotificationInterceptor);
    }
}

// This is the interceptor implementation
public class NhChangeNotificationInterceptorImpl : EmptyInterceptor, IInterceptor
{
    [Inject]
    public ISessionFactory SessionFactory { get; set; }

    [Inject]
    public ViewModelProxyFactory ProxyFactory { get; set; }

    public override object Instantiate(string entityTypeName, EntityMode entityMode, object id)
    {
        Type type = Type.GetType(entityTypeName); 

        if (type == null) { /* Throw Exception*/ }
        bool isViewModel = false;
        while (type != typeof(object))
        {
            Type tempType = type.BaseType;
            if (tempType == typeof(ViewModelBase))
            {
                isViewModel = true;
                break;
            }
        }

        if (entityMode == EntityMode.Poco && isViewModel)
        {
            var instance = ProxyFactory.CreateProxy(type);
            SessionFactory.GetClassMetadata(entityTypeName).SetIdentifier(instance, id, entityMode);
            return instance;
        }
        return base.Instantiate(entityTypeName, entityMode, id);
    }
}

The ProxyFactory uses Castle to create proxies that add change notification functionality. That means all my objects come from the DB as Castle Proxies, which are AFAIK transparent.

Whenever I pass one of those NH Generated MVVM-proxies into Session.Save(), all’s fine.

Now, as data driven Applications go, I also need to create new instances and save them. I can create instances of the model type and save them via the session all right. Creating a MVVM proxy instance (using Ninject to ensure that the same SessionFactory and ProxyFactory instances are used all over) and throwing this into Session.Save() results in the following:

---

"NHibernate.MappingException".
  Message=No persister for: Castle.Proxies.FieldDescriptionProxy
  Source=NHibernate
  StackTrace:
       at NHibernate.Impl.SessionFactoryImpl.GetEntityPersister(String entityName)
       at NHibernate.Impl.SessionImpl.GetEntityPersister(String entityName, Object obj)
       at NHibernate.Event.Default.AbstractSaveEventListener.SaveWithGeneratedId(Object entity, String entityName, Object anything, IEventSource source, Boolean requiresImmediateIdAccess)
       at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.SaveWithGeneratedOrRequestedId(SaveOrUpdateEvent event)
       at NHibernate.Event.Default.DefaultSaveEventListener.SaveWithGeneratedOrRequestedId(SaveOrUpdateEvent event)
       at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.EntityIsTransient(SaveOrUpdateEvent event)
       at NHibernate.Event.Default.DefaultSaveEventListener.PerformSaveOrUpdate(SaveOrUpdateEvent event)
       at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.OnSaveOrUpdate(SaveOrUpdateEvent event)
       at NHibernate.Impl.SessionImpl.FireSave(SaveOrUpdateEvent event)
       at NHibernate.Impl.SessionImpl.Save(Object obj)
       at Interpretation.UI.Service.Impl.Dao.FieldDao.SaveFields(IList`1 fields, ISession session) in C:\...\FieldDao.cs:Zeile 51.
  InnerException: 

---

Any ideas what goes wrong here (or what I might have forgotten)?

EDIT : Now got it working, but why do I have to add recognition logic (see code below) to the interceptor for instances created outside, while instances created inside can be persisted as the are?

    public override string GetEntityName(object entity)
    {
        Type type = entity.GetType();
        if (type.FullName.StartsWith("Castle.Proxies") &&
            type.FullName.EndsWith("Proxy"))
        {
            return type.BaseType.FullName;
        }
        return base.GetEntityName(entity);
    }

Answer 1

Implementing the GetEntityName method did the trick.

public override string GetEntityName(object entity)
{
    Type type = entity.GetType();
    if (type.FullName.StartsWith("Castle.Proxies") &&
        type.FullName.EndsWith("Proxy"))
    {
        return type.BaseType.FullName;
    }
    return base.GetEntityName(entity);
}