在C#中實現AES加密可以通過使用AesManaged類來實現。下面是一個簡單的示例代碼：

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

public class AesEncryption
{
    public static string Encrypt(string plainText, string key, string iv)
    {
        byte[] keyBytes = Encoding.UTF8.GetBytes(key);
        byte[] ivBytes = Encoding.UTF8.GetBytes(iv);

        byte[] encryptedBytes;

        using (AesManaged aes = new AesManaged())
        {
            aes.Key = keyBytes;
            aes.IV = ivBytes;

            ICryptoTransform encryptor = aes.CreateEncryptor(aes.Key, aes.IV);

            using (MemoryStream ms = new MemoryStream())
            {
                using (CryptoStream cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
                {
                    using (StreamWriter sw = new StreamWriter(cs))
                    {
                        sw.Write(plainText);
                    }

                    encryptedBytes = ms.ToArray();
                }
            }
        }

        return Convert.ToBase64String(encryptedBytes);
    }

    public static string Decrypt(string encryptedText, string key, string iv)
    {
        byte[] keyBytes = Encoding.UTF8.GetBytes(key);
        byte[] ivBytes = Encoding.UTF8.GetBytes(iv);

        byte[] encryptedBytes = Convert.FromBase64String(encryptedText);
        string decryptedText;

        using (AesManaged aes = new AesManaged())
        {
            aes.Key = keyBytes;
            aes.IV = ivBytes;

            ICryptoTransform decryptor = aes.CreateDecryptor(aes.Key, aes.IV);

            using (MemoryStream ms = new MemoryStream(encryptedBytes))
            {
                using (CryptoStream cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Read))
                {
                    using (StreamReader sr = new StreamReader(cs))
                    {
                        decryptedText = sr.ReadToEnd();
                    }
                }
            }
        }

        return decryptedText;
    }
}

使用以上代碼，你可以通過調用AesEncryption.Encrypt方法進行加密，調用AesEncryption.Decrypt方法進行解密。請注意，你需要提供一個密鑰（key）和一個初始化向量（iv），這兩個值必須是相同的才能正確解密。