You can use binding expressions:
private void ComboBox_Loaded(object sender, RoutedEventArgs e)
{
((ComboBox)sender).GetBindingExpression(ComboBox.ItemsSourceProperty)
.UpdateTarget();
}
But as Blindmeis noted you can also fire change notifications, further if your collection implements INotifyCollectionChanged
(for example implemented in the ObservableCollection<T>
) it will synchronize so you do not need to do any of this.