[C#/WPF] ListBox에서 SelectedItem의 위치로 스크롤 움직이기 (Behavior)

▶ 선택되어진 SelectedItem의 위치로 스크롤 이동시키기 Behavior 입니다.

public class ListBoxScrollIntoViewBehavior : Behavior<ListBox>
{
    protected override void OnAttached()
    {
        base.OnAttached();
        AssociatedObject.SelectionChanged += AssociatedObject_SelectionChanged;
    }

    protected override void OnDetaching()
    {
        AssociatedObject.SelectionChanged -= AssociatedObject_SelectionChanged;
        base.OnDetaching();
    }

    private static void AssociatedObject_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        var listBox = sender as ListBox;

        if (listBox?.SelectedItem == null)
            return;

        Action action = () =>
        {
            listBox.UpdateLayout();

            // 선택된 아이템으로 스크롤 이동시키기.
            if (listBox.SelectedItem != null)
                listBox.ScrollIntoView(listBox.SelectedItem);
        };

        listBox.Dispatcher.BeginInvoke(action, DispatcherPriority.ContextIdle);
    }
}

▶ Xaml에서 사용

<ScrollViewer VerticalScrollBarVisibility="Auto">
    <ListBox ItemsSource="{Binding TestItemSource}" SelectionMode="Extended">
        <i:Interaction.Behaviors>
            <behavior:ListBoxScrollIntoViewBehavior />
        </i:Interaction.Behaviors>
        ...
    </ListBox>
</ScrollViewer>