public void writeByteArrayToFile(byte[] buff, string fileName)
{
 
     try
     {
               FileStream fs = new FileStream(fileName, FileMode.Create, FileAccess.ReadWrite);
               BinaryWriter bw = new BinaryWriter(fs);
               bw.Write(buff);
               bw.Close();

      }
      catch (Exception ex)
      {
              Console.WriteLine(ex.Message);
      }
}