在c#中实现AES 256解密的方法如下：

1. 导入必要的命名空间

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

2. 定义解密方法

public static string AESDecrypt(string encryptedText, string password, string salt) { byte[] encryptedBytes = Convert.FromBase64String(encryptedText); byte[] saltBytes = Encoding.Unicode.GetBytes(salt);

Rfc2898DeriveBytes keyGenerator = new Rfc2898DeriveBytes(password, saltBytes, 1000);
byte[] keyBytes = keyGenerator.GetBytes(32);
byte[] ivBytes = keyGenerator.GetBytes(16);

using(Aes aes = Aes.Create())
{
    aes.Key = keyBytes;
    aes.IV = ivBytes;

    using(MemoryStream ms = new MemoryStream())
    {
        using(CryptoStream cs = new CryptoStream(ms, aes.CreateDecryptor(), CryptoStreamMode.Write))
        {
            cs.Write(encryptedBytes, 0, encryptedBytes.Length);
        }
        return Encoding.Unicode.GetString(ms.ToArray());
    }
}

}

3. 调用解密方法

string encryptedText = "加密后的文本"; string password = "密码"; string salt = "盐值";

string decryptedText = AESDecrypt(encryptedText, password, salt);

解密后的文本即为 decryptedText。