C# rijndael，字符集转换导致麻烦

使用C#的Rijndael算法解决字符集转换问题

csharp
using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
class RijndaelExample
{
    static void Main()
    {
        string originalText = "Hello, World! 你好，世界！";
        // 加密
        string encryptedText = Encrypt(originalText, "mySecretKey");
        Console.WriteLine($"加密后的文本: {encryptedText}");
        // 解密
        string decryptedText = Decrypt(encryptedText, "mySecretKey");
        Console.WriteLine($"解密后的文本: {decryptedText}");
    }
    static string Encrypt(string plainText, string key)
    {
        using (RijndaelManaged rijndael = new RijndaelManaged())
        {
            rijndael.Key = Encoding.UTF8.GetBytes(key);
            rijndael.Mode = CipherMode.ECB;
            ICryptoTransform encryptor = rijndael.CreateEncryptor(rijndael.Key, rijndael.IV);
            using (MemoryStream msEncrypt = new MemoryStream())
            {
                using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                {
                    using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                    {
                        swEncrypt.Write(plainText);
                    }
                }
                return Convert.ToBase64String(msEncrypt.ToArray());
            }
        }
    }
    static string Decrypt(string cipherText, string key)
    {
        using (RijndaelManaged rijndael = new RijndaelManaged())
        {
            rijndael.Key = Encoding.UTF8.GetBytes(key);
            rijndael.Mode = CipherMode.ECB;
            ICryptoTransform decryptor = rijndael.CreateDecryptor(rijndael.Key, rijndael.IV);
            using (MemoryStream msDecrypt = new MemoryStream(Convert.FromBase64String(cipherText)))
            {
                using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                {
                    using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                    {
                        return srDecrypt.ReadToEnd();
                    }
                }
            }
        }
    }
}