C#

public partial class DoubleBufferPractice : Form
    {
        Timer timer;
        Rectangle rect;

        public DoubleBufferPractice()
        {
            InitializeComponent();
            this.SetStyle(ControlStyles.OptimizedDoubleBuffer, true);
            this.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
            this.SetStyle(ControlStyles.UserPaint, true);
            rect = new Rectangle(0, this.Height/3, 50, 50);
            InitializeTimer();
        }

        private void InitializeTimer()
        {
            timer = new Timer();
            timer.Interval = 10;
            timer.Tick += new EventHandler(timer_Tick);
            timer.Start();
        }

        private void timer_Tick(object sender, EventArgs e) 
        {
            if(rect.X + rect.Width < this.Width)
                rect.X += 10;
            else
                rect.X = 0;
            this.Invalidate();
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            using(Graphics g = this.CreateGraphics()) {
                using(Brush brush = new SolidBrush(Color.Magenta)) {
                    g.FillRectangle(brush, rect);
                }
            }
            base.OnPaint(e);
        }
    }