Question

我有一个上传图片的小服务，我就这样使用它：

ImageInfo result = await service.UploadAsync(imagePath);

我想要做的是显示进度对话框，但前提是上传操作需要的时间超过2秒。上传完成后，我想关闭进度对话框。

我使用Task / ContinueWith做了一个粗略的解决方案，但我希望有一种更“优雅”的方式。

如何使用async/await实现此目的？

Answer 1

可能是这样的吗？

var uploadTask = service.UploadAsync(imagePath);
var delayTask = Task.Delay(1000);//Your delay here
if (await Task.WhenAny(new[] { uploadTask, delayTask }) == delayTask)
{
    //Timed out ShowProgress
    ShowMyProgress();
    await uploadTask;//Wait until upload completes
    //Hide progress
    HideProgress();
}

Answer 2

我以为我仍然会发布我的解决方案，因为它说明了如何显示和关闭模态对话框。它适用于WPF，但同样的概念适用于WinForms。

private async void OpenCommand_Executed(object sCommand, ExecutedRoutedEventArgs eCommand)
{
    // start the worker task
    var workerTask = Task.Run(() => {
        // the work takes at least 5s
        Thread.Sleep(5000);
    });

    // start timer task
    var timerTask = Task.Delay(2000);
    var task = await Task.WhenAny(workerTask, timerTask);

    if (task == timerTask)
    {
        // create the dialog
        var dialogWindow = CreateDialog();

        // go modal
        var modalityTcs = new TaskCompletionSource<bool>();

        dialogWindow.Loaded += (s, e) =>
            modalityTcs.SetResult(true);

        var dialogTask = Dispatcher.InvokeAsync(() =>
            dialogWindow.ShowDialog());

        await modalityTcs.Task;

        // we are now on the modal dialog Dispatcher frame
        // the main window UI has been disabled

        // now await the worker task
        await workerTask;

        // worker task completed, close the dialog
        dialogWindow.Close();
        await dialogTask;

        // we're back to the main Dispatcher frame of the UI thread
    }
}

仅当任务未在指定时间内完成时才显示进度对话框

2 个答案: