主要是Hex，Base64, Utf-8 和 byte[] 互转。

    class Program
    {
        static void Main(string[] args)
        {
            string str = "abccba";
            Console.WriteLine("原字符串:" + str);
            byte[] byteData = Encoding.UTF8.GetBytes(str);
            {
                string hexlower = Byte2HexLower(byteData);
                Console.WriteLine("转HEX:" + hexlower);
                byte[] byteTemp = Hex2Byte(hexlower);
                Console.WriteLine("转回字符串:" + Encoding.UTF8.GetString(byteTemp));
            }
            {
                string base64 = Convert.ToBase64String(byteData);
                Console.WriteLine("转base64:" + base64);
                byte[] byteTemp = Convert.FromBase64String(base64);
                Console.WriteLine("转回字符串:" + Encoding.UTF8.GetString(byteTemp));
            }

            Console.ReadLine();
        }
        static string Byte2HexLower(byte[] byteData)
        {
            return BitConverter.ToString(byteData, 0).Replace("-", string.Empty).ToLower();
        }

        public static byte[] Hex2Byte(string hexString)
        {
            hexString = hexString.Replace(" ", "");
            byte[] returnBytes = new byte[hexString.Length / 2];
            for (int i = 0; i < returnBytes.Length; i++)
            {
                returnBytes[i] = Convert.ToByte(hexString.Substring(i * 2, 2), 16);
            }

            return returnBytes;
        }