System.Security.Cryptography.CryptoStream.FlushFinalBlock C# (CSharp) Method

        public void FlushFinalBlock()
        {
            if (_finalBlockTransformed)
                throw new NotSupportedException(SR.Cryptography_CryptoStream_FlushFinalBlockTwice);
            // We have to process the last block here.  First, we have the final block in _InputBuffer, so transform it

            byte[] finalBytes = _transform.TransformFinalBlock(_inputBuffer, 0, _inputBufferIndex);

            _finalBlockTransformed = true;
            // Now, write out anything sitting in the _OutputBuffer...
            if (_canWrite && _outputBufferIndex > 0)
            {
                _stream.Write(_outputBuffer, 0, _outputBufferIndex);
                _outputBufferIndex = 0;
            }
            // Write out finalBytes
            if (_canWrite)
                _stream.Write(finalBytes, 0, finalBytes.Length);

            // If the inner stream is a CryptoStream, then we want to call FlushFinalBlock on it too, otherwise just Flush.
            CryptoStream innerCryptoStream = _stream as CryptoStream;
            if (innerCryptoStream != null)
            {
                if (!innerCryptoStream.HasFlushedFinalBlock)
                {
                    innerCryptoStream.FlushFinalBlock();
                }
            }
            else
            {
                _stream.Flush();
            }
            // zeroize plain text material before returning
            if (_inputBuffer != null)
                Array.Clear(_inputBuffer, 0, _inputBuffer.Length);
            if (_outputBuffer != null)
                Array.Clear(_outputBuffer, 0, _outputBuffer.Length);
            return;
        }

 public static string Encrypt(string plainText, string passPhrase)
 {
     byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);
     using (PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null))
     {
         byte[] keyBytes = password.GetBytes(keysize / 8);
         using (RijndaelManaged symmetricKey = new RijndaelManaged())
         {
             symmetricKey.Mode = CipherMode.CBC;
             using (ICryptoTransform encryptor = symmetricKey.CreateEncryptor(keyBytes, initVectorBytes))
             {
                 using (MemoryStream memoryStream = new MemoryStream())
                 {
                     using (CryptoStream cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
                     {
                         cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
                         cryptoStream.FlushFinalBlock();
                         byte[] cipherTextBytes = memoryStream.ToArray();
                         return Convert.ToBase64String(cipherTextBytes);
                     }
                 }
             }
         }
     }
 }