Cipher

class AEScbcCipher
    {
        private int AESblockSize;
        private byte[] keyByte = new byte[16];
        private byte[] ivByte = new byte[16];
        private string keyString = "xxx";
        private string ivString = "xxx";

        public AEScbcCipher(int AESblockSize)
        {
            this.AESblockSize = AESblockSize;
            setKey();
            setIV();
        }
        public AEScbcCipher()
        {
            this.AESblockSize = 16;
            setKey();
            setIV();
        }

        private void setKey()
        {
            for (int j = 0; j < keyByte.Length; j += 2)
            {
                byte result;
                if (byte.TryParse(keyString.Substring(j, 2), System.Globalization.NumberStyles.HexNumber, System.Globalization.CultureInfo.CreateSpecificCulture("en-US"), out result) == true)
                {
                    keyByte[j / 2] = result;
                }
            }
        }
        private void setIV()
        {
            for (int j = 0; j < ivByte.Length; j += 2)
            {
                byte result;
                if (byte.TryParse(ivString.Substring(j, 2), System.Globalization.NumberStyles.HexNumber, System.Globalization.CultureInfo.CreateSpecificCulture("en-US"), out result) == true)
                {
                    ivByte[j / 2] = result;
                }
            }
        }

        private byte[] PerformCryptography(ICryptoTransform cryptoTransform, byte[] data)
        {
            using (var memoryStream = new MemoryStream())
            {
                using (var cryptoStream = new CryptoStream(memoryStream, cryptoTransform, CryptoStreamMode.Write))
                {
                    //I get Exception here
                    cryptoStream.Write(data, 0, data.Length);
                    cryptoStream.FlushFinalBlock();
                    return memoryStream.ToArray();
                }
            }
        }

        public byte[] Encrypt(byte[] data)
        {
            if (data == null || data.Length <= 0)
                throw new ArgumentNullException("plainText");
            if (keyByte == null || keyByte.Length <= 0)
                throw new ArgumentNullException("Key");
            if (ivByte == null || ivByte.Length <= 0)
                throw new ArgumentNullException("IV");
            using (Aes aesAlg = Aes.Create())
            {
                aesAlg.Key = keyByte;
                aesAlg.IV = ivByte;
                using (var encryptor = aesAlg.CreateEncryptor(keyByte, ivByte))
                {
                    return PerformCryptography(encryptor, data);
                }
                //unreachable code
                return data;
            }

        }

        public byte[] Decrypt(byte[] data)
        {
            using (Aes aesAlg = Aes.Create())
            {
                aesAlg.Key = keyByte;
                aesAlg.IV = ivByte;
                using (var decryptor = aesAlg.CreateDecryptor(keyByte, ivByte))
                {
                    return PerformCryptography(decryptor, data);
                }
                //unreachable code
                return data;
            }
        }
}
}