private Image CreateBitmap()

{

    System.Drawing.Bitmap flag = new System.Drawing.Bitmap(10, 10);

    for (int x = 0; x < flag.Height; ++x)

        for (int y = 0; y < flag.Width; ++y)

            flag.SetPixel(x, y, Color.White);

    for (int x = 0; x < flag.Height; ++x)

        flag.SetPixel(x, x, Color.Red);

    return flag;

}



private void Form1_Load(object sender, EventArgs e)

{

    pictureBox1.Image = CreateBitmap();

}

منبع : http://msdn2.microsoft.com/en-us/library/aa287582(VS.71).aspx