Sven Groot said:

Best I can think of is to save the bitmap (using the Save method) to a MemoryStream, then read out the MemoryStream into a byte array.

EDIT: So, basically:

System.Drawing.Bitmap bmp = GetTheBitmap();
System.IO.MemoryStream stream = new System.IO.MemoryStream();
bmp.Save(stream, System.Drawing.Imaging.ImageFormat.Bmp);
stream.Position = 0;
byte[] data = new byte[stream.Length];
stream.Read(data, 0, stream.Length);

That MemoryStream would include the Bitmap file header, you'll need to manually truncate the first 14 bytes.