Random random = new Random();
Color getRandomColor()
{
return Color.FromArgb(
random.Next(256) ,
random.Next(256) ,
random.Next(256) );
}
private void button1_Click(object sender, System.EventArgs e)
{
Graphics g = this.CreateGraphics();
int x0 = this.Width /2;
int y0 = this.Height /2;
for( int r=0 ; r<this.Height/2; r++ )
{
g.DrawEllipse(
new Pen( getRandomColor(),1),
x0-r,y0-r, r*2, r*2
);
}
g.Dispose();
}