static void Main(string[] args)

        {

            //string str = "rqiJI7eEICT+YZmScpAdbjzLnA4mgL3uU5uHXLBeaE6s8P3noNriVQZ/fO52ar8I9BSkVZIiyP8ArdG/KkXZi5Cn8rZaOVyEjgqhfFlTRIg=";

            string str = "{ \"UserID\":1,\"Email\":null,\"LoginTime\":\"2018 - 12 - 12T11: 25:38.6208949 + 08:00\"";

            string result = EncodeAES(str, "yhkZvOJSnTHG9hKT", "yhkZvOJSnTHG9hKT");

            Console.WriteLine(result);

            //Console.WriteLine(DecodeAES(str, "ptQJqRKxICCTeo6w", "O3vZvOJSnQDP9hKT"));

            Console.ReadKey();

        }

public static string EncodeAES(string text, string key, string iv)

        {

            RijndaelManaged rijndaelCipher = new RijndaelManaged();

            rijndaelCipher.Mode = CipherMode.CBC;

            rijndaelCipher.Padding = PaddingMode.Zeros;

            rijndaelCipher.KeySize = ;

            rijndaelCipher.BlockSize = ;

            byte[] pwdBytes = System.Text.Encoding.UTF8.GetBytes(key);

            byte[] keyBytes = new byte[];

            int len = pwdBytes.Length;

            if (len > keyBytes.Length)

                len = keyBytes.Length;

            System.Array.Copy(pwdBytes, keyBytes, len);

            rijndaelCipher.Key = keyBytes;

            rijndaelCipher.IV = Encoding.UTF8.GetBytes(iv);

            ICryptoTransform transform = rijndaelCipher.CreateEncryptor();

            byte[] plainText = Encoding.UTF8.GetBytes(text);

            byte[] cipherBytes = transform.TransformFinalBlock(plainText, , plainText.Length);

            return Convert.ToBase64String(cipherBytes);

        }

public static string DecodeAES(string text, string key, string iv)

{

RijndaelManaged rijndaelCipher = new RijndaelManaged();

rijndaelCipher.Mode = CipherMode.CBC;

rijndaelCipher.Padding = PaddingMode.Zeros;

rijndaelCipher.KeySize = ;

rijndaelCipher.BlockSize = ;

byte[] encryptedData = Convert.FromBase64String(text);

byte[] pwdBytes = System.Text.Encoding.UTF8.GetBytes(key);

byte[] keyBytes = new byte[];

int len = pwdBytes.Length;

if (len > keyBytes.Length)

len = keyBytes.Length;

System.Array.Copy(pwdBytes, keyBytes, len);

rijndaelCipher.Key = keyBytes;

rijndaelCipher.IV = Encoding.UTF8.GetBytes(iv);

ICryptoTransform transform = rijndaelCipher.CreateDecryptor();

byte[] plainText = transform.TransformFinalBlock(encryptedData, , encryptedData.Length);

return Encoding.UTF8.GetString(plainText);

}