用c#截图桌面

我得到一个错误，说在运行时Save()行上需要编码器参数。我不知道我应该为这个参数写什么。什么好主意吗?

using (Bitmap bmpScreenCapture = new Bitmap(Screen.PrimaryScreen.Bounds.Width, Screen.PrimaryScreen.Bounds.Height))
{
                using (Graphics g = Graphics.FromImage(bmpScreenCapture))
                {
                    g.CopyFromScreen(Screen.PrimaryScreen.Bounds.X,
                                     Screen.PrimaryScreen.Bounds.Y,
                                     0, 0,
                                     bmpScreenCapture.Size,
                                     CopyPixelOperation.SourceCopy);
                    MemoryStream ms = new MemoryStream();
                    bmpScreenCapture.Save(ms, bmpScreenCapture.RawFormat);   // <---- ERROR
                    byte[] bytes = ms.GetBuffer();
                    ms.Close();
                }
}