WPF TreeView: How to style selected items with rounded corners like in Explorer

Question

The selected item in a WPF TreeView has a dark blue background with \"sharp\" corners. That looks a bit dated today:

Answer 1

Windows 10 TreeView (and ListView) Style

I was originally looking for a way to apply the Windows 10 color scheme to a TreeViewItem, including

• IsMouseOver on current item only
• Windows 10 colors which WPF already applies them to ListBox (not Windows Explorer)

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If any of you are looking for exactly this, please feel free to take the code below. I used Helge Klein's solution for the IsMouseOver issue and applied the Windows 10 colors to the XAML. Therefore I propose this as an addition to the accepted answer.

Also, see below for a word on ListView and ComboBox as well.

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Screenshot

App.xaml

TreeViewItemHelper (by Helge Klein, minor changes / simplification)

public static class TreeViewItemHelper
{
    private static TreeViewItem CurrentItem;
    private static readonly RoutedEvent UpdateOverItemEvent = EventManager.RegisterRoutedEvent("UpdateOverItem", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(TreeViewItemHelper));
    private static readonly DependencyPropertyKey IsMouseDirectlyOverItemKey = DependencyProperty.RegisterAttachedReadOnly("IsMouseDirectlyOverItem", typeof(bool), typeof(TreeViewItemHelper), new FrameworkPropertyMetadata(null, new CoerceValueCallback(CalculateIsMouseDirectlyOverItem)));
    public static readonly DependencyProperty IsMouseDirectlyOverItemProperty = IsMouseDirectlyOverItemKey.DependencyProperty;

    static TreeViewItemHelper()
    {
        EventManager.RegisterClassHandler(typeof(TreeViewItem), UIElement.MouseEnterEvent, new MouseEventHandler(OnMouseTransition), true);
        EventManager.RegisterClassHandler(typeof(TreeViewItem), UIElement.MouseLeaveEvent, new MouseEventHandler(OnMouseTransition), true);
        EventManager.RegisterClassHandler(typeof(TreeViewItem), UpdateOverItemEvent, new RoutedEventHandler(OnUpdateOverItem));
    }
    public static bool GetIsMouseDirectlyOverItem(DependencyObject obj)
    {
        return (bool)obj.GetValue(IsMouseDirectlyOverItemProperty);
    }
    private static object CalculateIsMouseDirectlyOverItem(DependencyObject item, object value)
    {
        return item == CurrentItem;
    }
    private static void OnUpdateOverItem(object sender, RoutedEventArgs e)
    {
        CurrentItem = sender as TreeViewItem;
        CurrentItem.InvalidateProperty(IsMouseDirectlyOverItemProperty);
        e.Handled = true;
    }
    private static void OnMouseTransition(object sender, MouseEventArgs e)
    {
        lock (IsMouseDirectlyOverItemProperty)
        {
            if (CurrentItem != null)
            {
                DependencyObject oldItem = CurrentItem;
                CurrentItem = null;
                oldItem.InvalidateProperty(IsMouseDirectlyOverItemProperty);
            }

            Mouse.DirectlyOver?.RaiseEvent(new RoutedEventArgs(UpdateOverItemEvent));
        }
    }
}

ListBox/ListView and ComboBox: In Windows 7 (and 8?), this will cause the design from TreeView to ListBox/ListView and ComboBox to differ. Therefore, if you want to apply this color scheme to these control types as well, too, use this: