Code example: Just try to refacoter your code based on this and see what happens.
class FooObservableCollection : ObservableCollection<Foo>
{
protected override void InsertItem(int index, Foo item)
{
base.Add(index, Foo);
if (this.CollectionChanged != null)
this.CollectionChanged(this, new NotifyCollectionChangedEventArgs (NotifyCollectionChangedAction.Add, item, index);
}
}
var collection = new FooObservableCollection();
collection.CollectionChanged += CollectionChanged;
collection.Add(new Foo());
void CollectionChanged (object sender, NotifyCollectionChangedEventArgs e)
{
Foo newItem = e.NewItems.OfType<Foo>().First();
}