不使用pictureBox!!!

我是这样写的,可不见图,说 System.Drawing.Bitmap并不包含FromFile的定义!
这是怎么回事???

 private void Form1_Paint(object sender, PaintEventArgs e)
 {
        backImage = Bitmap.FromFile("Background.bmp");
        g = this.CreateGraphics();
        g.DrawImage(backImage, 0, 0);
}