try like this, and check VS console for exception:
public byte[] imageToByteArray(System.Drawing.Image imageIn)
{
if (imageIn!=null){
using (var ms = new MemoryStream())
{
try{
imageIn.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
return ms.ToArray();
}
catch(Exception ex){
Console.WriteLine("See me:"+ex.Message);
}
}
} else return null;
}