Pretty simple question here. If you use a gdi+ item to draw some text, how do you go back to it and update it or clear it.

protected override void OnPaint(PaintEventArgs pe)
{
Font fnt = new Font("Verdana", 16);
Graphics g = pe.Graphics;

// Main Title Bar
g.DrawString("SELECT OPERATIONAL MODE", fnt, new SolidBrush(Color.Yellow), 230, 50);

...
}

I don't see any means to remove or update something that was drawn.
Can someone give some input on my view of this problem and if possible, how to attack it?