Taking a screen shot of a game (Counter-Strike 1.6)

[Ornakash]

Hello guys. I am trying to take a screen shot while I am ingame (counter-strike). When I try to take a screenshot it gives me a black picture. It happens only when I am in-game (when I am in desktop and take a screenshot, it works). Someone told me that this game uses OpenGL and maybe that is the problem. This is the code I use:

private Image CaptureScreen()
        {
            Rectangle screenSize = Screen.PrimaryScreen.Bounds;
            Bitmap target = new Bitmap(screenSize.Width, screenSize.Height);
            using (Graphics g = Graphics.FromImage(target))
            {
                g.CopyFromScreen(0, 0, 0, 0, new Size(screenSize.Width, screenSize.Height));
            }
            return target;
        }

thanks in advance.