private void button2_Click(object sender, EventArgs e)
{
Random r = new Random();
Bitmap b = new Bitmap(Width, Height);
Graphics g = Graphics.FromImage(b);
SolidBrush br = new SolidBrush(Color.FromArgb(150, r.Next(255),
r.Next(255), r.Next(255)));
g.FillRectangle(br,0,0,Width,Height);
pictureBox1.Image = b;
}