AESManaged文件加解密和前置初始化向量

我正在尝试加密/解密字节-我已经使用System.Security.Cryptography中的AESManaged类做了很多关于AES算法的密钥和IV的阅读。我读了James Johnson对以下问题http://www.techques.com/question/1-7025135/My-Length-of-the-data-to-decrypt-is-invalid-error的回答，他建议您在加密例程中使用随机IV，并将IV添加到加密消息之前。解密函数从加密消息的开头去掉随机的IV来初始化解密类，然后解密其余的字节。我已经尝试在下面的代码中做到这一点。但是，当我在加密后尝试解密时，我一直得到"要解密的数据长度无效"的错误消息。有没有人能告诉我哪里出了问题?

       USAGE: (streamToEncrypt/streamToDecrypt are System.IO.Stream)

       using (var cryptoHelper = new AESHelper())
        {
            var encryptedBytes = cryptoHelper.Encrypt(AESHelper.StreamToByteArray(streamToEncrypt));
        }

using (var cryptoHelper = new AESHelper())
        {
            var decryptedBytes = cryptoHelper.Decrypt(AESHelper.StreamToByteArray(streamToDecrypt));                             
        }
 public class AESHelper : IDisposable
 {       
    public AesManaged AESManaged;
    internal ICryptoTransform Encryptor { get; set; }
    internal ICryptoTransform Decryptor { get; set; }
    private const string KEY = "2428GD19569F9B2C2341839416C8E87G";
    private static readonly byte[] Salt = Encoding.ASCII.GetBytes("?pt1$8f]l4g80");
    private const Int32 ITERATIONS = 1042;

    internal AESHelper()
    {
        AESManaged = new AesManaged();
        AESManaged.BlockSize = AESManaged.LegalBlockSizes[0].MaxSize;
        AESManaged.KeySize = AESManaged.LegalKeySizes[0].MaxSize;                    
        AESManaged.Mode= CipherMode.CBC;
    }
   public void KeyGenerator()
    {
        var key = new Rfc2898DeriveBytes(KEY, Salt, ITERATIONS);
        AESManaged.Key = key.GetBytes(AESManaged.KeySize / 8);           
    }
    public byte[] Encrypt(byte[] input)
    {
        KeyGenerator();
        var ms = new MemoryStream();
        //Random IV 
        Encryptor = AESManaged.CreateEncryptor(AESManaged.Key, AESManaged.IV);
        //Add the IV to the beginning of the memory stream
        ms.Write(BitConverter.GetBytes(AESManaged.IV.Length), 0, sizeof(int));
        ms.Write(AESManaged.IV, 0, AESManaged.IV.Length);
        var cs = new CryptoStream(ms,
          Encryptor, CryptoStreamMode.Write);
        cs.Write(input, 0, input.Length);
        cs.Close();
        return ms.ToArray();
    }
    public byte[] Decrypt(byte[] input)
    {
        KeyGenerator();
        // Get the initialization vector from the encrypted stream
        var ms = new MemoryStream(input);
        AESManaged.IV = ReadByteArray(ms);
        Decryptor = AESManaged.CreateDecryptor(AESManaged.Key, AESManaged.IV);
        var cs = new CryptoStream(ms,
         Decryptor, CryptoStreamMode.Write);
        cs.Write(input, 0, input.Length);
        cs.Close();//Error occurs here
        return ms.ToArray();
    }
    internal static byte[] ReadByteArray(Stream s)
    {
        var rawLength = new byte[sizeof(int)];
        if (s.Read(rawLength, 0, rawLength.Length) != rawLength.Length)
        {
            throw new SystemException("Stream did not contain properly formatted byte array");
        }
        var buffer = new byte[16];
        if (s.Read(buffer, 0, buffer.Length) != buffer.Length)
        {
            throw new SystemException("Did not read byte array properly");
        }
        return buffer;
    }
     internal static byte[] StreamToByteArray(Stream inputStream)
    {
        if (!inputStream.CanRead)
        {
            throw new ArgumentException();
        }
        // This is optional
        if (inputStream.CanSeek)
        {
            inputStream.Seek(0, SeekOrigin.Begin);
        }
        var output = new byte[inputStream.Length];
        var bytesRead = inputStream.Read(output, 0, output.Length);
        Debug.Assert(bytesRead == output.Length, "Bytes read from stream matches stream length");
        return output;
    }
  public void Dispose()
    {
        if (AESManaged != null)
            ((IDisposable) AESManaged).Dispose();
    }}

Many Thanks in advance