加密時：先對string進行utf8解析成數組-->對數組進行加密-->對加密結果用base64解析成string。

那麽揭秘時，對字符串的解析方式是必須要“倒”過來的，就成這樣子了：

解密時：先對string進行base64解析成數組-->對數組進行解密-->對解密結果用utf8解析成string

using System;
using System.Security.Cryptography;
using System.Text;

namespace ConsoleApp14
{
    public
 
 delegate void GreetDelegate(string name);
    class Program
    {
        private static void Main(string[] args)
        {
            string s = EncodeStr("Good");
            Console.WriteLine(s);
            string ss = "hFsfyUinz3jzjulh0y7HWw==";
            Console.WriteLine(DecodeStr(ss));
            Console.ReadKey();

        }
        
 
//加密和解密的密鑰必須相等。
        public static string EncodeStr(string ss)
        {
            string s = string.Empty;
            //設置密鑰
            byte[] keyArray = UTF8Encoding.UTF8.GetBytes("12345678901234567890123456789012");
            //加密時用utf8,當解密時要反過來
            byte[] toEncryptArray = UTF8Encoding.UTF8.GetBytes(ss);
            
 
//建立算法實例
            RijndaelManaged r = new RijndaelManaged();
            //設置屬性
            r.Key = keyArray;
            r.Mode = CipherMode.ECB;
            r.Padding = PaddingMode.PKCS7;
            //制定加密或者解密方式
            ICryptoTransform ic = r.CreateEncryptor();
         byte[] bb= ic.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
            //以base64進行加密輸出，當解密時要先用base64進行解析
            s = Convert.ToBase64String(bb);
            return s;
        }
        public static string DecodeStr(string ss)
        {
            string s = string.Empty;
            //設置密鑰
            byte[] keyArray = UTF8Encoding.UTF8.GetBytes("12345678901234567890123456789012");
            byte[] toEncryptArray = Convert.FromBase64String(ss);

            //建立算法實例
            RijndaelManaged r = new RijndaelManaged();
            //設置屬性
            r.Key = keyArray;
            r.Mode = CipherMode.ECB;
            r.Padding = PaddingMode.PKCS7;
            //制定加密或者解密方式
            ICryptoTransform ic = r.CreateDecryptor();
            byte[] bb = ic.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
            s = UTF8Encoding.UTF8.GetString(bb);
            return s;
        }

    }
}

Aes加密解密