how to store image in byte ?

You can do it in various ways. Here are some:

1st way:(By using MemoryStream)

public byte[] imageToByteArray(System.Drawing.Image img)
{
   byte[] byteArray = new byte[0];
   using (MemoryStream stream = new MemoryStream())
   {
      img.Save(stream, System.Drawing.Imaging.ImageFormat.Png);
      stream.Close();
      byteArray = stream.ToArray();
   }
   return byteArray;
}

2nd way:(By using System.Drawing.ImageConvertor)

public static byte[] ImageToByte(Image img)
{    
  ImageConverter converter = new ImageConverter();    
  return (byte[])converter.ConvertTo(img, typeof(byte[]));
}

Good luck,
OI