Try this:
Bitmap myBitmap = new Bitmap(300, 100, e.Graphics);
using (Graphics g = Graphics.FromImage(myBitmap))
{
g.Clear(Color.White);
g.DrawString("Test", textFont, Brushes.Black, 10, 20);
}
e.Graphics.DrawImage(myBitmap, new Point(0, 0));
e.Graphics.DrawString("Test", textFont, Brushes.Black, 10, 50);