SelectAndGiveFocusToFirstElementInListBoxBehaviour - example code for StackOverflow question 6467928

gistfile1.cs

    public class SelectAndGiveFocusToFirstElementInListBoxBehavior
    {
        public static readonly DependencyProperty EnabledProperty =
            DependencyProperty.RegisterAttached(
                "Enabled",
                typeof(bool),
                typeof(SelectAndGiveFocusToFirstElementInListBoxBehavior),
                new FrameworkPropertyMetadata(0, new PropertyChangedCallback(OnEnabledChanged)));

        public static bool GetEnabled(ListBox listBox) {...}

        public static void SetEnabled(ListBox listBox, bool value) {...}

        private static void OnEnabledChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs args)
        {
            var listBox = dependencyObject as ListBox;

            if (listBox != null)
            {
                ListenToItemsCollectionChange(listBox);               
            }
        }
        
        private static void ListenToItemsCollectionChange(ListBox listBox)
        {
            var collection = (INotifyCollectionChanged)listBox.Items;

            collection.CollectionChanged += (sender, args) => SelectAndSetFocusToFirstElementIfEnabled(listBox);
        }
        
        private static void SelectAndSetFocusToFirstElementIfEnabled(ListBox listBox)
        {
            if (GetEnabled(listBox))
            {
                SelectAndSetFocusToFirstElement(listBox);
            }
        }

        private static void SelectAndSetFocusToFirstElement(ListBox listBox) {...}
    }