直接上程式碼：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    public class AESEncrypt
    {
        //向量偏移
        private static string _key1 = "********";

        
 
#region AES 加密
        /// <summary>
        ///  AES 加密
        /// </summary>
        /// <param name="str">明文（待加密）</param>
        /// <param name="key">密文</param>
        /// <returns></returns>
        public static string AesEncrypt(string str, string key)
        {
            
 
if (string.IsNullOrEmpty(str)) return null;
            Byte[] toEncryptArray = Encoding.UTF8.GetBytes(str);

            RijndaelManaged rm = new RijndaelManaged
            {
                Key = Encoding.UTF8.GetBytes(key),
                IV = Encoding.UTF8.GetBytes(_key1),
                Mode 
 
= CipherMode.CBC,
                Padding = PaddingMode.PKCS7
            };
            ICryptoTransform cTransform = rm.CreateEncryptor();
            Byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
            return Convert.ToBase64String(resultArray, 0, resultArray.Length);
        }
        #endregion

        #region AES 解密
        /// <summary>
        ///  AES 解密
        /// </summary>
        /// <param name="str">明文（待解密）</param>
        /// <param name="key">密文</param>
        /// <returns></returns>
        public static string AesDecrypt(string str, string key)
        {
            if (string.IsNullOrEmpty(str)) return null;
            Byte[] toEncryptArray = Convert.FromBase64String(str);
            RijndaelManaged rm = new RijndaelManaged
            {
                Key = Encoding.UTF8.GetBytes(key),
                IV = Encoding.UTF8.GetBytes(_key1),
                Mode = CipherMode.CBC,
                Padding = PaddingMode.PKCS7
            };
            ICryptoTransform cTransform = rm.CreateDecryptor();
            Byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
            return Encoding.UTF8.GetString(resultArray);
        }
        #endregion
    }
}