using System;
using System.Security.Cryptography;
using System.Text;
public class Program
{
    public static void Main()
    {
        // Encryption using RijndaelManaged (not recommended)
        string plainText = "Hello, World!";
        byte[] key = Encoding.UTF8.GetBytes("0123456789ABCDEF");
        byte[] iv = Encoding.UTF8.GetBytes("1234567890ABCDEF");

        using (var rijndael = new RijndaelManaged())
        {
            rijndael.Key = key;
            rijndael.IV = iv;

            byte[] encryptedData = Encrypt(plainText, rijndael);
            string decryptedText = Decrypt(encryptedData, rijndael);

            Console.WriteLine("RijndaelManaged - Encrypted Data: " +
                Convert.ToBase64String(encryptedData));
            Console.WriteLine("RijndaelManaged - Decrypted Text: " + 
                                           decryptedText);
        }

        Console.WriteLine();

        // Encryption using AesManaged (recommended)
        using (var aes = new AesManaged())
        {
            aes.Key = key;
            aes.IV = iv;

            byte[] encryptedData = Encrypt(plainText, aes);
            string decryptedText = Decrypt(encryptedData, aes);

            Console.WriteLine("AesManaged - Encrypted Data: " + 
                Convert.ToBase64String(encryptedData));
            Console.WriteLine("AesManaged - Decrypted Text: " + 
                decryptedText);
        }
    }

    public static byte[] Encrypt(string plainText,
                                                SymmetricAlgorithm algorithm)
    {
        byte[] encryptedData;

        using (var encryptor = algorithm.CreateEncryptor())
        {
            byte[] plainBytes = Encoding.UTF8.GetBytes(plainText);

            encryptedData = encryptor.TransformFinalBlock(plainBytes, 
                                             0, plainBytes.Length);
        }

        return encryptedData;
    }

    public static string Decrypt(byte[] encryptedData,
                                                SymmetricAlgorithm algorithm)
    {
        string decryptedText;

        using (var decryptor = algorithm.CreateDecryptor())
        {
            byte[] decryptedBytes = decryptor.TransformFinalBlock(
                                                        encryptedData, 
                                                        0, encryptedData.Length);

            decryptedText = Encoding.UTF8.GetString(decryptedBytes);
        }

        return decryptedText;
    }
}