public static class OutsideCloser
    {
        public static readonly DependencyProperty CloseProperty =
            DependencyProperty.RegisterAttached(
                "Close",
                typeof(bool),
                typeof(OutsideCloser),
                new FrameworkPropertyMetadata(PropertyChangedCallback));

        [AttachedPropertyBrowsableForType(typeof(Window))]
        public static void SetClose(Window target, bool value)
        {
            target.SetValue(CloseProperty, value);
        }

        [AttachedPropertyBrowsableForType(typeof(Window))]
        public static bool GetClose(Window target)
        {
            return (bool)target.GetValue(CloseProperty);
        }

        private static void PropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            if (d is Window window)
            {
                window.Loaded += Window_Loaded;
                window.Closed += Window_Closed;
                window.LostMouseCapture += Window_LostMouseCapture;
            }
        }

        private static void Window_LostMouseCapture(object sender, MouseEventArgs e)
        {
            var window = (Window)sender!;
            Mouse.Capture(window, CaptureMode.SubTree);
        }

        private static void Window_Closed(object? sender, EventArgs e)
        {
            var window = (Window)sender!;

            window.LostMouseCapture -= Window_LostMouseCapture;
            window.Closed -= Window_Closed;
            window.Loaded -= Window_Loaded;

            window.RemoveHandler(Mouse.PreviewMouseDownOutsideCapturedElementEvent,
                (MouseButtonEventHandler)HandleClickOutsideOfControl);
            window.ReleaseMouseCapture();
        }

        private static void Window_Loaded(object sender, RoutedEventArgs e)
        {
            var window = (Window)sender;
            Mouse.Capture(window, CaptureMode.SubTree);
            window.AddHandler(Mouse.PreviewMouseDownOutsideCapturedElementEvent,
                (MouseButtonEventHandler)HandleClickOutsideOfControl);
        }

        private static void HandleClickOutsideOfControl(object sender, MouseButtonEventArgs e)
        {
            var window = (Window)sender;
            var owner = window.Owner;
            var point = e.MouseDevice.GetPosition(owner);

            if (point.X >= 0 && point.X <= owner.ActualWidth && point.Y >= 0 && point.Y <= owner.ActualHeight)
            {
                window.Close();
            }
        }
    }