当我将控制台输出重定向到richtextbox时，程序挂起

Question

当我从代码调用外部exe并将输出重定向到我的UI richtextbox后，UI挂起并且没有在屏幕上显示输出，它慢慢启动延迟UI屏幕上的输出，任何人都知道为什么这是发生了。这是我的代码

private void RunExe(string arg)
    {
        var cmdStartInfo = new ProcessStartInfo
        {
            Arguments = arg,
            FileName = System.IO.Path.Combine(Application.StartupPath, @"Demo.exe"),
            CreateNoWindow = true,
            RedirectStandardInput = true,
            RedirectStandardOutput = true,
            RedirectStandardError = true,
            UseShellExecute = false,
            WindowStyle = ProcessWindowStyle.Hidden
        };
        _cmd = new Process {StartInfo = cmdStartInfo};
        _cmd.OutputDataReceived +=new DataReceivedEventHandler(OutputHandler);
        _cmd.Start();
        ProcessId = _cmd.Id;
        _enableButton = new Task(_cmd_Exited);
        _enableButton.Start();
        MyTabControl.Visibility = Visibility.Visible;
        if (!MyTabControl.Items.Contains(ConsoleTabItem))
        {
            MyTabControl.Items.Add(ConsoleTabItem);
        }
        txtConsoleOutput.Document.Blocks.Clear();
        ConsoleTabItem.Focus();
        ConsoleTabItem.Visibility = Visibility.Visible;
        ConsoleTabItem.IsEnabled = false;
        _cmd.BeginOutputReadLine();
        LoadResults();
    }

输出处理程序

private void OutputHandler(object sender, DataReceivedEventArgs e)
    {
        try
        {
            if (e.Data != null)
            {
                string line;
                Dispatcher.Invoke(() =>
                {
                    line = e.Data;
                    if (line != null)
                    {
                        txtConsoleOutput.AppendText(line + "\n");
                        ConsoleScrollerView.ScrollToBottom();
                    }
                });
            }
        }
        catch (NullReferenceException ex)
        {
            Console.WriteLine(ex);
        }
    }

我真的很感激任何帮助..谢谢