C# AES要解密的数据的长度无效

 
public  string Decrypt(string toDecrypt, string key)
{
            SymmetricAlgorithm des = Rijndael.Create();
            byte[] inputByteArray = Encoding.UTF8.GetBytes(toDecrypt);
            des.Key = Encoding.UTF8.GetBytes(key);
            des.IV = des.Key;
            des.Mode = CipherMode.CBC;
            des.Padding = PaddingMode.PKCS7;

            ICryptoTransform cTransform = des.CreateEncryptor();

            return UTF8Encoding.UTF8.GetString(cTransform.TransformFinalBlock(inputByteArray, 0, inputByteArray.Length));
}