Sample code for a blog post I wrote about: WPF Bindings Not Updating When PropertyChanged Raised When Bound Against a Proxy Object

ExampleConfig.xml

<hibernate-configuration  xmlns="urn:nhibernate-configuration-2.2" >
    <session-factory name="YourAppName">
        <property name="connection.driver_class">NHibernate.Driver.SqlClientDriver</property>
        <property name="dialect">NHibernate.Dialect.MsSql2005Dialect</property>
        <property name="connection.connection_string">
            Server=(local);initial catalog=nhibernate;Integrated Security=SSPI
        </property>
        <property name="proxyfactory.factory_class"> YouProjectNameSpace.FixDataBindingProxyFactoryFactory, YourProjectAssembly</property>
    </session-factory>
</hibernate-configuration>

ExampleOfProblem.cs

public class ShoppingCart : INotifyPropertyChanged
{
    public virtual Guid Id { get; private set; }

    public virtual IList<CartItem> _items = new ObservableCollection<CartItem>();

    public virtual IEnumerable<CartItem> { get { return _items; } }
	
    public virtual decimal Total { get { return _items.Sum(i => i.Price); } }
	
    public virtual void AddItem(CartItem item)
    {
        _items.Add(item);
		
        // We raise this event to notify subscribers that our Total has very likely changed its value.
        PropertyChanged(this, new PropertyChangedEventArgs("Total"));
    }
	
    public virtual event PropertyChangedEventHandler PropertyChanged = delegate {};
}

FixDataBindingLazyInitializer.cs

public class FixDataBindingLazyInitializer : LazyInitializer
{
	private PropertyChangedEventHandler _subscribers = delegate { };
	public object ProxyInstance { get; set; }

	public FixDataBindingInterceptor(String entityName, Type persistentClass, object id, MethodInfo getIdentifierMethod, MethodInfo setIdentifierMethod, IAbstractComponentType aType, ISessionImplementor session)
		: base(entityName, persistentClass, id, getIdentifierMethod, setIdentifierMethod, aType, session)
	{
	}

	public override void Intercept(Castle.DynamicProxy.IInvocation invocation)
	{
		// WPF will call a method named add_PropertyChanged to subscribe itself to the property changed events of
		// the given entity. The method to call is stored in invocation.Arguments[0]. We get this and add it to the
		// proxy subscriber list.
		if (invocation.Method.Name.EndsWith("PropertyChanged"))
		{
			PropertyChangedEventHandler propertyChangedEventHandler = (PropertyChangedEventHandler)invocation.Arguments[0];
			if (invocation.Method.Name.StartsWith("add_"))
			{
				_subscribers += propertyChangedEventHandler;
			}
			else
			{
				_subscribers -= propertyChangedEventHandler;
			}
		}
		else
		{
			base.Intercept(invocation);
		}            
	}

	public override void Initialize()
	{
		base.Initialize();

		var notifyPropertyChanged = Target as INotifyPropertyChanged;

		if (notifyPropertyChanged != null)
		{
			// We subscribe to our Target's property changed event so we can pass it on
			// to any objects that subscribe to the proxies event.
			notifyPropertyChanged.PropertyChanged += TargetPropertyChanged;
		}
	}

	void TargetPropertyChanged(object sender, PropertyChangedEventArgs e)
	{
		_subscribers(ProxyInstance, e);
	}
}

FixDataBindingProxyFactory.cs

public class FixDataBindingProxyFactory : ProxyFactory
{
	public override INHibernateProxy GetProxy(object id, ISessionImplementor session)
	{
		// If it is not a proxy for a class do what you usually did.
		if (!IsClassProxy) return base.GetProxy(id, session);

		try
		{
			var initializer = new FixDataBindingLazyInitializer(EntityName, PersistentClass, id,
					   GetIdentifierMethod, SetIdentifierMethod, ComponentIdType, session);

			// Add to the list of the interfaces that the proxy class will support the INotifyPropertyChanged interface.
			// This is only needed in the case when we need to cast our proxy object as INotifyPropertyChanged interface.
			var extraInterfaces = new[] {typeof (INotifyPropertyChanged)};
			
			var interfaces = Interfaces.Concat(extraInterfaces).ToArray();

			object generatedProxy = DefaultProxyGenerator.CreateClassProxy(PersistentClass, interfaces, initializer);

			initializer._constructed = true;
			initializer.ProxyInstance = generatedProxy;
			return (INHibernateProxy)generatedProxy;
		}
		catch (Exception e)
		{
			log.Error("Creating a proxy instance failed", e);
			throw new HibernateException("Creating a proxy instance failed", e);
		}
	}
}

FixDataBindingProxyFactoryFactory.cs

public class FixDataBindingProxyFactoryFactory : IProxyFactoryFactory
{
	public IProxyFactory BuildProxyFactory()
	{
		return new FixDataBindingProxyFactory();
	}

	public bool IsInstrumented(Type entityClass)
	{
		return true;
	}

	public IProxyValidator ProxyValidator
	{
		get { return new DynProxyTypeValidator(); }
	}
}

Can you please update the code to use the new build in proxy in NH >= 3.3