compressing bytes

[C# Programming]

hi I have this code that convert an picture box image in bytes

MemoryStream ms = new MemoryStream();
pictureBox1.Image.Save(ms, ImageFormat.Jpeg);
byte[] data = ms.ToArray();
ms.Close();
MessageBox.Show("image Converted in bytes");

now i want to compress these bytes too according to this code
plz help me