WPF: Hit testing is slow.

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        this.Loaded += MainWindow_Loaded;
    }

    public Canvas canvas;
    Random random = new Random();
    int add = 5;

    Timer timerEllipses;

    void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        canvas = new Canvas();
        canvas.Background = Brushes.Black;
        this.Content = canvas;

        timerEllipses = new Timer();
        timerEllipses.Interval = 1;
        timerEllipses.Start();

        Timer timer = new Timer();
        timer.Interval = 2000;
        timer.Elapsed += timer_Elapsed;
        timer.Start();
    }

    void timer_Elapsed(object sender, ElapsedEventArgs e)
    {
        this.Dispatcher.Invoke((Action)(() =>
        {
            int add = this.add;

            int x = random.Next((int)canvas.ActualWidth);
            int y = random.Next((int)canvas.ActualHeight);

            for (int i1 = 0; i1 < canvas.ActualWidth; i1++)
                for (int i2 = 0; i2 < canvas.ActualHeight; i2++)
                    VisualTreeHelper.HitTest(canvas, new Point(i1, i2)); // Slows down

            Ellipse ellipse = new Ellipse();
            ellipse.Width = 1;
            ellipse.Height = 1;
            ellipse.Stroke = Brushes.White;
            canvas.Children.Add(ellipse);

            timerEllipses.Elapsed += delegate
            {
                this.Dispatcher.Invoke((Action)(() =>
                {
                    ellipse.Width += add;
                    ellipse.Height += add;

                    ellipse.Margin = new Thickness(x - (ellipse.Width / 2), y - (ellipse.Height / 2), 0, 0);

                }));
            };
        }));
    }
}

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        this.Loaded += MainWindow_Loaded;
    }

    public Canvas canvas;
    Random random = new Random();

    Ellipse ellipse;
    int add = 5;
    double x = 0;
    double y = 0;

    Stopwatch stopwatch = new Stopwatch();
    public double elapsed = 10;

    void MainWindow_Loaded(object sender, RoutedEventArgs e)
    {
        canvas = new Canvas();
        canvas.Background = Brushes.Black;
        this.Content = canvas;

        ellipse = new Ellipse();
        ellipse.Width = 1;
        ellipse.Height = 1;
        ellipse.Stroke = Brushes.White;
        canvas.Children.Add(ellipse);

        new System.Threading.Thread(Thread1).Start();
    }

    void Thread1()
    {
        stopwatch.Start();

        while (true)
        {
            if (stopwatch.Elapsed.TotalMilliseconds >= elapsed)
            {
                stopwatch.Stop();

                this.Dispatcher.Invoke((Action)(() =>
                {
                    for (int i1 = 0; i1 < canvas.ActualWidth; i1++)
                        for (int i2 = 0; i2 < canvas.ActualHeight; i2++)
                            VisualTreeHelper.HitTest(canvas, new Point(i1, i2)); // Slows down

                    ellipse.Width += add;
                    ellipse.Height += add;

                    ellipse.Margin = new Thickness(x - (ellipse.Width / 2), y - (ellipse.Height / 2), 0, 0);
                }));

                stopwatch.Restart();
            }
        }
    }
}