Visual Basic

Public Sub Save(ByVal carrier As DataCarrier, ByVal password As String, ByVal filename As String)
            Try
                Using sha As New SHA512Managed
                    Dim salt As Byte() = sha.ComputeHash(Encoding.Default.GetBytes(password))
                    Using pdb As New Rfc2898DeriveBytes(password, salt), aes As New RijndaelManaged, filestr As New FileStream(filename, FileMode.Create, FileAccess.Write)
                        Using cryptostr As New CryptoStream(filestr, aes.CreateEncryptor(pdb.GetBytes(32), pdb.GetBytes(16)), CryptoStreamMode.Write)
                            Dim str = ExportData(carrier).ToString()
                            Using w As New StreamWriter(cryptostr)
                                w.Write(str)
                            End Using
                        End Using
                    End Using
                End Using
            Catch ex As Exception
                Logging.Instance.WriteException(ex, TraceEventType.Error)
                MessageBox.Show(String.Format(My.Resources.UnhandledExceptionExString, ex.Message, ex.ToString), My.Application.Info.Title, MessageBoxButtons.OK, MessageBoxIcon.Error)
            End Try
        End Sub

Public Sub Save(ByVal carrier As DataCarrier, ByVal password As String, ByVal filename As String)
           Try
               Using sha As New SHA512Managed
                   Dim salt As Byte() = sha.ComputeHash(Encoding.Default.GetBytes(password))
                   Using pdb As New Rfc2898DeriveBytes(password, salt), aes As New RijndaelManaged, filestr As New MemoryStream() 'filestr As New FileStream(filename, FileMode.Create, FileAccess.Write)
                       Using cryptostr As New CryptoStream(filestr, aes.CreateEncryptor(pdb.GetBytes(32), pdb.GetBytes(16)), CryptoStreamMode.Write)
                           ExportData(carrier).Save(cryptostr)
                           Dim str = New String(Encoding.Default.GetChars(filestr.ToArray()))
                           Debugger.Break()
                       End Using
                   End Using
               End Using
           Catch ex As Exception
               Logging.Instance.WriteException(ex, TraceEventType.Error)
               MessageBox.Show(String.Format(My.Resources.UnhandledExceptionExString, ex.Message, ex.ToString), My.Application.Info.Title, MessageBoxButtons.OK, MessageBoxIcon.Error)
           End Try
       End Sub

Public Sub Save(ByVal carrier As DataCarrier, ByVal password As String, ByVal filename As String)
            Try
                Using sha As New SHA512Managed
                    Dim salt As Byte() = sha.ComputeHash(Encoding.Default.GetBytes(password))
                    Using pdb As New Rfc2898DeriveBytes(password, salt), aes As New RijndaelManaged, filestr As New MemoryStream() 'filestr As New FileStream(filename, FileMode.Create, FileAccess.Write)
                        Using cryptostr As New CryptoStream(filestr, aes.CreateEncryptor(pdb.GetBytes(32), pdb.GetBytes(16)), CryptoStreamMode.Write)
                            ExportData(carrier).Save(cryptostr)
                            File.WriteAllBytes(filename, filestr.ToArray())
                            Debugger.Break()
                        End Using
                    End Using
                End Using
            Catch ex As Exception
                Logging.Instance.WriteException(ex, TraceEventType.Error)
                MessageBox.Show(String.Format(My.Resources.UnhandledExceptionExString, ex.Message, ex.ToString), My.Application.Info.Title, MessageBoxButtons.OK, MessageBoxIcon.Error)
            End Try
        End Sub

1. Comment out the export line and perform the crypto-stream write directly.
2. Create two byte arrays for the key and IV and make sure pdb is creating a sensible key & IV, I would have thought that the if these were incorrect the encryption algorithm would throw. I've not used the derived bytes thing, so it is new to me
3. If the above isn't working, hard-code the key and IV byte arrays

Public Sub Save(ByVal carrier As DataCarrier, ByVal password As String, ByVal filename As String)
        Try
            Using sha As New SHA512Managed
                Dim hash = sha.ComputeHash(Encoding.Default.GetBytes(password))
                Dim key As Byte() = New Byte(31) {}
                Dim iv As Byte() = New Byte(15) {}
                Array.Copy(hash, 0, key, 0, 32)
                Array.Copy(hash, 32, iv, 0, 16)
                Using aes As New RijndaelManaged, filestr As New FileStream(filename, FileMode.Create, FileAccess.Write)
                    Using cryptostr As New CryptoStream(filestr, aes.CreateEncryptor(key, iv), CryptoStreamMode.Write)
                        ExportData(carrier).Save(cryptostr)
                    End Using
                End Using
            End Using
        Catch ex As Exception
            Logging.Instance.WriteException(ex, TraceEventType.Error)
            MessageBox.Show(String.Format(My.Resources.UnhandledExceptionExString, ex.Message, ex.ToString), My.Application.Info.Title, MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try
    End Sub
    Public Function Load(ByVal password As String, ByVal filename As String) As XDocument
        Dim sha As SHA512Managed
        Dim aes As RijndaelManaged
        Dim trans As ICryptoTransform
        Dim cryptostr As CryptoStream
        Dim filestr As FileStream
        Try
            sha = New SHA512Managed()
            Dim hash = sha.ComputeHash(Encoding.Default.GetBytes(password))
            aes = New RijndaelManaged()
            Dim key As Byte() = New Byte(31) {}
            Dim iv As Byte() = New Byte(15) {}
            Array.Copy(hash, 0, key, 0, 32)
            Array.Copy(hash, 32, iv, 0, 16)
            trans = aes.CreateEncryptor(key, iv)
            filestr = New FileStream(filename, FileMode.Open)
            cryptostr = New CryptoStream(filestr, trans, CryptoStreamMode.Read)
            Return XDocument.Load(cryptostr)
        Catch ex As Exception
            Logging.Instance.WriteException(ex, TraceEventType.Error)
            MessageBox.Show(String.Format(My.Resources.UnhandledExceptionExString, ex.Message, ex.ToString), My.Application.Info.Title, MessageBoxButtons.OK, MessageBoxIcon.Error)
        Finally
            If cryptostr IsNot Nothing Then cryptostr.Dispose()
            If filestr IsNot Nothing Then filestr.Dispose()
            If trans IsNot Nothing Then trans.Dispose()
            If aes IsNot Nothing Then aes.Dispose()
            If sha IsNot Nothing Then sha.Dispose()
        End Try
    End Function

Public Shared Function Encrypt(value As String, key() As Byte, iv() As Byte) As string
    Dim bytValue() As Byte      'The data to be encrypted
    Dim bytEncoded() As Byte    'The data after encryption
    Dim rijndael As New Rijndael Managed
    Dim ms As New MemoryStream  'The stream to write the encrypted data to
    
    bytValue = Encoding.ASCII.GetBytes(value.ToCharArray)   'Convert plain text to byte array
    'Create the crypto stream with the stream to write the encrypted data to (ms = Memory Stream)
    Using CryptoStream As New CryptoStream(ms, rijnadel.CreateEncryptor(key, iv), CryptoStreamMode.Write)
        'Encrypt the plaint text byte array (bytValue) to the memory stream (ms)
        CryptoStream.Write(bytValue, 0, bytValue.Length)
        'Flush crypto stream
        CryptoStream.FlushFinalBlock()
        'Get the encrypted byte array from the memory stream (ms)
        bytEncoded = ms.ToArray
        'Close memory stream
        ms.Close()
    End Using
    
    'Convert the encrypted byte array (bytEncoded) to a Base64 string and return it
    Return Convert.ToBase64String(bytEncoded)
End Function