Follower

bool b = false;
        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            b = true;
            a.Clear();
        }

        private void Form1_MouseUp(object sender, MouseEventArgs e)
        {
            b = false;

        }
        ArrayList a = new ArrayList();
        Point[] p = new Point[50];
        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {
            if (b == true)
            {
                a.Add(new Point(e.X, e.Y));
                if (a.Count >= 50)
                {
                    for (int i = 0; i < a.Count - 50; i++)
                    {
                        a.RemoveAt(i);
                    }

                    a.CopyTo(p);
                }
                else
                {
                    a.CopyTo(p);
                }
                Bitmap bp = new Bitmap(this.Width, this.Height);
                Graphics g = Graphics.FromImage(bp);
                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;
                Pen pn = new Pen(Brushes.Black);
                pn.Width = 2;
                pn.DashStyle = System.Drawing.Drawing2D.DashStyle.Dash;
                g.DrawLines(pn, p);
                this.BackgroundImage = bp;
            }