Public Overridable Event CollectionChanged As NotifyCollectionChangedEventHandler

Dim instance As ObservableCollection
Dim handler As NotifyCollectionChangedEventHandler

AddHandler instance.CollectionChanged, handler

public virtual event NotifyCollectionChangedEventHandler CollectionChanged

public:
virtual  event NotifyCollectionChangedEventHandler^ CollectionChanged {
    void add (NotifyCollectionChangedEventHandler^ value);
    void remove (NotifyCollectionChangedEventHandler^ value);
}

JScript does not support events.

<object CollectionChanged="NotifyCollectionChangedEventHandler" .../>