参考文章： C#软件加密实例？ 。
参考官文： Aes 类。

在使用C#的自带的System.Security.Cryptography.Aes模块进行加密和解密时，需要注意的点是：定义用于对称算法的密钥Key和初始化向量IV。
如果不定义，就算是对相同字符串加密，每次得到的加密结果也都不一样。

1 代码

1.1 定义Aes加密类块

using System.IO;
using System.Security.Cryptography;

namespace Encryption
{
    internal class AesModule
    {
        Aes myAes = null;

        public AesModule()
        {
            // 创建一个Aes对象
            myAes = Aes.Create();
            // 【key的值获取方法见2.1】 
            myAes.Key = new byte[32] { 0xDD, 0xB7, 0xAA, 0xE5, 0xC6, 0x68, 0x95, 0x39, 0x72, 0x7C, 0x7F, 0xDC, 0x5B, 0xC9, 0x77, 0x21, 0x62, 0x59, 0xC4, 0x92, 0xBC, 0x7D, 0x44, 0xA7, 0x3D, 0x02, 0x37, 0x7B, 0x3C, 0x19, 0xEB, 0x7F };
            // 【IV的值获取方法见2.1】
            myAes.IV = new byte[16] { 0x84, 0xAA, 0xCD, 0x08, 0x21, 0xCE, 0x4D, 0xA7, 0x7B, 0x34, 0xD9, 0x9F, 0x28, 0x51, 0x8A, 0xEB };
        }
        ~AesModule()
        {
            myAes.Dispose();
        }
        /// <summary>
        /// 将字符串加密为字节数组
        /// </summary>
        /// <param name="original">待加密的字符串</param>
        /// <returns>加密好的字节数组</returns>
        public byte[] EncryptAes(string original)
        {
            if (original == null || original.Length <= 0) return null;
            byte[] encrypted;
            // 创建一个加密器来执行流转换。
            ICryptoTransform encryptor = myAes.CreateEncryptor(myAes.Key, myAes.IV);

            // 创建加密流。
            using (MemoryStream msEncrypt = new MemoryStream())
            {
                using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                {
                    using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                    {
                        //将原始文本写入流。
                        swEncrypt.Write(original);
                    }
                    encrypted = msEncrypt.ToArray();
                }
            }
            return encrypted;
        }
        /// <summary>
        /// 将字节数组解密为字符串
        /// </summary>
        /// <param name="bArr">待解密的字节数组</param>
        /// <returns>解密好的字符串</returns>
        public string DecryptAes(byte[] bArr)
        {
            if (bArr == null || bArr.Length <= 0) return null;

            string plaintext = null;

            ICryptoTransform decryptor = myAes.CreateDecryptor(myAes.Key, myAes.IV);
            using (MemoryStream msDecrypt = new MemoryStream(bArr))
            {
                using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                {
                    using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                    {
                        // 从解密流中读取解密的字节。
                        plaintext = srDecrypt.ReadToEnd();
                    }
                }
            }
            return plaintext;
        }
    }
}

1.2 在主函数中调用

internal class Program
{
    static void Main(string[] args)
    {
        string original = "Here is some data to encrypt!";

        AesModule aes = new AesModule();	// 创建自定义Aes模块的对象
        Console.WriteLine("Original:   {0}", original);
        byte[] bArr = aes.EncryptAes(original);	// 加密
        Console.WriteLine("Encrypted:  {0}", BitConverter.ToString(bArr));
        Console.WriteLine("Decrypted: {0}", aes.DecryptAes(bArr));	// 解密
        Console.ReadLine();
    }
}

调用结果：

Original:   Here is some data to encrypt!
Encrypted:  6B-AB-9D-2A-54-16-59-1B-B7-5F-5C-F5-43-6B-D0-C2-E3-6A-72-98-8D-42-99-D9-38-DC-20-09-9C-94-6B-27
Decrypted: Here is some data to encrypt!

2 获取Key和IV

2.1 基本方法

其实方法就是：
定义Aes对象，然后调用它的函数GenerateXXX()方法，来生成Key和IV，并且写死到程序中。

internal class demo
{
    static void Main()
    {    	
    	using (Aes myAes = Aes.Create())	// 定义Aes对象
        {
            myAes.GenerateKey();			// 生成key
            Console.WriteLine("Key");			
            PrintBytes(myAes.Key);	
            		
            myAes.GenerateIV();				// 生成IV
            Console.WriteLine("IV");
            PrintBytes(myAes.IV);
        }
        Console.ReadLine();
    }
    /// <summary>
	/// 输出字节数组，加0x并按逗号分割
	/// </summary>
	/// <param name="bArr">待输出字节数组</param>
	static void PrintBytes(byte[] bArr)
	{
	    for (int i = 0; i < bArr.Length; i++)
	    {
	        if (i != 0) Console.Write(",");
	        Console.Write("0x" + bArr[i].ToString("X2")); // 其中"X2"表示以大写十六进制格式输出，并且占两个字符的宽度（不足两位时前面补0）
	    }
	    Console.WriteLine();
	}
}

得到结果(每次运行都不一样)：

Key
0xDD,0xB7,0xAA,0xE5,0xC6,0x68,0x95,0x39,0x72,0x7C,0x7F,0xDC,0x5B,0xC9,0x77,0x21,0x62,0x59,0xC4,0x92,0xBC,0x7D,0x44,0xA7,0x3D,0x02,0x37,0x7B,0x3C,0x19,0xEB,0x7F
IV
0x84,0xAA,0xCD,0x08,0x21,0xCE,0x4D,0xA7,0x7B,0x34,0xD9,0x9F,0x28,0x51,0x8A,0xEB

将结果拷贝到代码中下述位置即可：

myAes.Key = new byte[32] { 【key】};
myAes.IV = new byte[16] {【IV】};

2.2 自定义Key

如果你想要生成自定义的Key，那么，也可以使用如下方法来生成。

byte[] key = Encoding.UTF8.GetBytes("Heisagoodboyandwillfindtruelove!");
PrintBytes(key);

会得到专属Key:

0x48,0x65,0x69,0x73,0x61,0x67,0x6F,0x6F,0x64,0x62,0x6F,0x79,0x61,0x6E,0x64,0x77,0x69,0x6C,0x6C,0x66,0x69,0x6E,0x64,0x74,0x72,0x75,0x65,0x6C,0x6F,0x76,0x65,0x21

2.3 技术方面的原理

这里仅略述该预定义AES类的使用原理：
Key定义了get-set函数，而且会自动生成Key，其源代码如下：

public virtual byte[] Key
{
    get
    {
        if (KeyValue == null)
        {
            GenerateKey();
        }
        ...
    }
    set
    {
        ...
        KeyValue = (byte[])value.Clone();
    }
}

IV类似。