public class Helper
    {
        public static string Bytes2Hex(byte[] bytes, int index, int count)
        {
            try
            {
                return BitConverter.ToString(bytes, index, count).Replace("-", String.Empty);
            }
            catch { }

            return string.Empty;
        }

        public static string Bytes2Hex(byte[] bytes)
        {
            try
            {
                return BitConverter.ToString(bytes).Replace("-", String.Empty);
            }
            catch { }

            return string.Empty;
        }
        
        public static byte[] Hex2Bytes(string hex, int index, int length)
        {
            return Hex2Bytes(hex.Substring(index, length));
        }

        public static byte[] Hex2Bytes(string hex)
        {
            byte[] bytes = new byte[hex.Length / 2];
            for (int i = 0; i < bytes.Length; i++)
                bytes[i] = Convert.ToByte(hex.Substring(2 * i, 2), 16);
            return bytes;            
        }
    }