Defrag Output in C#

Sorry if this has been posted somewhere before, but I have several problems when trying to use the Windows disk defragmenter in C#.

I would like to run the defrag.exe process from within my application, and show real-time feedback.

I have written something like the code below:

        private void defragAction(object sender, RoutedEventArgs e)
        {
            System.Threading.Thread workT = new System.Threading.Thread(new System.Threading.ThreadStart(new Action(
     delegate
     {
         System.Diagnostics.Process defragProcess = new Process();

            defragProcess.StartInfo.FileName = "defrag.exe";
            string letter = curInfo.Name.Substring(0, 1).ToUpper();
            defragProcess.StartInfo.Arguments = letter + @": -f";
            defragProcess.StartInfo.RedirectStandardInput = true;
            defragProcess.StartInfo.RedirectStandardOutput = true;
            defragProcess.StartInfo.UseShellExecute = false;
            defragProcess.StartInfo.CreateNoWindow = true;
            defragProcess.EnableRaisingEvents = true;
            defragProcess.OutputDataReceived += defragOutputRecieved;
            defragProcess.StartInfo.WindowStyle = ProcessWindowStyle.Normal;

            defragProcess.Start();
                    defragProcess.BeginOutputReadLine();
                }
            )));
            workT.Start();

I then have another method to recieve the output:

private void defragOutputRecieved(object sender, DataReceivedEventArgs e)
        {
            Application.Current.Dispatcher.Invoke(new Action(
                delegate
                {
                    MessageBox.Show(e.Data);
                }));
        }

The problem is that the output stream is only read when the defrag process has finished or is cancelled. I need real-time user feedback in my application.

I don't understand as Process.BeginOutputReadLine() is supposed to be an asynchronous operation.

Has anyone got any suggestions on how I can make this work?

Thanks.