Question

我在WPF中有以下代码，我的问题是：

如何使用并行任务和后台工作者更新我的文本框？我知道我的错误是在txtResult1.text个事件中写txtResult2.text，txtResult3.text，worker_DoWork。但是如何解决这个问题？
代码需要ReadLineAsync和WriteLineAsync吗？

这是我的代码：

    public MainWindow()
    {
        InitializeComponent();
    }
    private readonly BackgroundWorker worker = new BackgroundWorker();
    private void btnStart_Click(object sender, RoutedEventArgs e)
    {
        worker.DoWork +=worker_DoWork;
        worker.RunWorkerCompleted += worker_RunWorkerCompleted;
        worker.WorkerReportsProgress = true;
        worker.RunWorkerAsync();
    }

    void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        MessageBox.Show("Done");
    }

    private void worker_DoWork(object sender, DoWorkEventArgs e)
    {
        Parallel.Invoke(() =>
                    {  Task.Run(() => txtResult1.text = ReadCharacter("C:\\File 1.txt")); },
                    () =>
                    { Task.Run(()  => txtResult2.text = ReadCharacter("C:\\File 2.txt")); },
                    () =>
                    { Task.Run(()  => txtResult3.text = ReadCharacter("C:\\File 3.txt")); }
                    );

    }

    private string ReadCharacter(string inputFile)
    {
        string result; string TID;           
        using (StreamReader sr =new StreamReader(inputFile))
        using (StreamWriter sw = new StreamWriter(string.Format("{0}--Out.txt", inputFile.Replace(".txt",""))))
        {
            var sb = new StringBuilder();

            TID = "Thread ID: "+ Thread.CurrentThread.ManagedThreadId.ToString();
            sb.AppendLine(TID);
            sb.AppendLine("T Start : " + DateTime.Now.ToLongTimeString() + "." + 
                    DateTime.Now.Millisecond).ToString();
            while (!sr.EndOfStream)
            {
                result = sr.ReadLine();
                sw.WriteLine(result);
            };

            return
            sb.AppendLine("T Stop : "+DateTime.Now.ToLongTimeString() + "." + 
                    DateTime.Now.Millisecond).ToString();
        } 
    }

Answer 1

您的方法存在一些问题：

Task.Run

Parallel.Invoke不会向您购买任何东西如果你想做并发I / O ，那么
Parallel是错误的解决方案 - Parallel用于并行CPU绑定操作。
BackgroundWorker在这一点上几乎是遗产。我有blog series that shows how Task.Run is better than BackgroundWorker。

另外，正如@HansPassnat指出的那样，你几乎肯定会不想要并发磁盘访问，因为这通常会大大减慢你的速度。

但如果你真的想这样做，我建议采用async方法：

private async void btnStart_Click(object sender, RoutedEventArgs e)
{
  var progress = new Progress<string>(value => { txtResult1.Text = value; });
  await Task.WhenAll(ReadCharacterAsync("C:\\File 1.txt", progress),
      ReadCharacterAsync("C:\\File 2.txt", progress),
      ReadCharacterAsync("C:\\File 3.txt", progress));
  MessageBox.Show("Done");
}

private async Task ReadCharacterAsync(string inputFile, IProgress<string> progress)
{
    string result; string TID;
    using (var inFile = new FileStream(inputFile, FileMode.Open, FileAccess.Read, FileShare.None, 8192, useAsync: true))
    using (var outFile = new FileStream(string.Format("{0}--Out.txt", inputFile.Replace(".txt","")), FileMode.Create, FileAccess.ReadWrite, FileShare.None, 8192, useAsync: true))
    using (StreamReader sr =new StreamReader(inFile))
    using (StreamWriter sw = new StreamWriter(outFile))
    {
        var sb = new StringBuilder();

        TID = "Thread ID: "+ Thread.CurrentThread.ManagedThreadId.ToString();
        sb.AppendLine(TID);
        sb.AppendLine("T Start : " + DateTime.Now.ToLongTimeString() + "." + 
                DateTime.Now.Millisecond).ToString();
        while (!sr.EndOfStream)
        {
            result = await sr.ReadLineAsync();
            await sw.WriteLineAsync(result);
        };

        progress.Report(
        sb.AppendLine("T Stop : "+DateTime.Now.ToLongTimeString() + "." + 
                DateTime.Now.Millisecond).ToString());
    } 
}

Answer 2

在WPF中，您必须使用Dispatcher访问其他线程的控件：

 Parallel.Invoke(() =>
                {  Task.Run(() => this.Dispatcher.BeginInvoke(new Action(() => 
                   txtResult1.Text += ReadCharacter("C:\\File 2.txt")); },
                )

Answer 3

您必须在处理事件的同一线程上设置文本框。您可以通过Task的{{1}}方法或在下面显示的方法中使用async / await（或其他解决方案中描述的.ContinueWith(...)方法）来执行此操作：

Dispatcher.BeginInvoke

用法：

private async Task GetDataAndSetTextBoxAsync( TextBox textBox, Func<char> dataMethod )
{
    var task = Task.StartNew( taskMethod );

    await task;

    // this will run on thread that called this method
    // in a WPF application
    textBox.Text = task.Result;
}

Async和Backgroundworker组合

3 个答案: