Make Bitmap On Startup

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();
}