如何在wpf后台执行任务同时提供报告并允许取消？

小编典典

如何在wpf后台执行任务同时提供报告并允许取消？

我想在单击wpf按钮后执行长时间运行的任务。这是我做的。

private void Start(object sender, RoutedEventArgs e)
{
    for (int i = 0; i < 10; i++)
    {
        Thread.Sleep(2000); // simulate task
    }
}

问题是，这会使wpf gui无法响应。我也想允许取消并每1秒报告一次进度。我将代码扩展如下。

    DispatcherTimer dispatcherTimer = new DispatcherTimer(); // get progress every second
    private int progress = 0; // for progress reporting
    private bool isCancelled = false; // cancellation

    private void Start(object sender, RoutedEventArgs e)
    {
        InitializeTimer(); // initiallize interval timer 
        Start(10); // execute task
    }

    private void InitializeTimer()
    {
        dispatcherTimer.Tick += dispatcherTimer_Tick;
        dispatcherTimer.Interval = new TimeSpan(0,0,1);
        dispatcherTimer.Start();
    }

    private void dispatcherTimer_Tick(object sender, EventArgs e)
    {
        Logger.Info("Current loop progress " + progress); // report progress
    }

    private void Cancel(object sender, RoutedEventArgs e) // cancel button
    {
        isCancelled = true;
    }

    private int Start(int limit)
    {
        isCancelled = true;
        progress = 0;

        for (int i = 0; i < limit; i++)
        {
            Thread.Sleep(2000); // simulate task
            progress = i; // for progress report
            if (isCancelled) // cancellation
            {
                break;
            }
        }
        return limit;
    }

我的目标平台是.NET 4.5。推荐的方法是什么？

谢谢。

阅读 356

2020-05-19

共1个答案

小编典典

我以为我在这里回答了你的问题。如果您需要有关如何使用Task
Parallel Library进行操作的更多示例代码，请使用CancellationTokenSource和IProgress<T>，这里是：

Action _cancelWork;

private async void StartButton_Click(object sender, RoutedEventArgs e)
{
    this.StartButton.IsEnabled = false;
    this.StopButton.IsEnabled = true;
    try
    {
        var cancellationTokenSource = new CancellationTokenSource();

        this._cancelWork = () => 
        {
            this.StopButton.IsEnabled = false;
            cancellationTokenSource.Cancel();
         };

        var limit = 10;

        var progressReport = new Progress<int>((i) => 
            this.TextBox.Text = (100 * i / (limit-1)).ToString() + "%");

        var token = cancellationTokenSource.Token;

        await Task.Run(() =>
            DoWork(limit, token, progressReport), 
            token);
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
    this.StartButton.IsEnabled = true;
    this.StopButton.IsEnabled = false;
    this._cancelWork = null;
}

private void StopButton_Click(object sender, RoutedEventArgs e)
{
    this._cancelWork?.Invoke();
}

private int DoWork(
    int limit, 
    CancellationToken token,
    IProgress<int> progressReport)
{
    var progress = 0;

    for (int i = 0; i < limit; i++)
    {
        progressReport.Report(progress++);
        Thread.Sleep(2000); // simulate a work item
        token.ThrowIfCancellationRequested();
    }
    return limit;
}

2020-05-19