Question

我需要做一个长期运行的任务。我已经通过执行任务来完成此操作，而UI上有一个加载框。抛出异常时，我想停止任务并向用户显示一个msgbox。如果一切顺利，我会停止装箱。

下面的代码按预期工作，但我想知道我在这里是否正确，因为这是我第一次这样做。

    private readonly CancellationTokenSource cancellationTokenSource = new CancellationTokenSource();

    protected void ProgramImage()
    {
        this.OnProgrammingStarted(new EventArgs());
        var task =
            Task.Factory.StartNew(this.ProgramImageAsync)
                .ContinueWith(
                    this.TaskExceptionHandler,
                    cancellationTokenSource.Token,
                    TaskContinuationOptions.OnlyOnFaulted,
                    TaskScheduler.FromCurrentSynchronizationContext())  //Catch exceptions here
                        .ContinueWith(
                            o => this.ProgramImageAsyncDone(),
                            cancellationTokenSource.Token,
                            TaskContinuationOptions.NotOnFaulted,
                            TaskScheduler.FromCurrentSynchronizationContext());  //Run this when no exception occurred
    }

    private void ProgramImageAsync()
    {
        Thread.Sleep(5000); // Actual programming is done here
        throw new Exception("test");
    }

    private void TaskExceptionHandler(Task task)
    {
        var exception = task.Exception;
        if (exception != null && exception.InnerExceptions.Count > 0)
        {
            this.OnProgrammingExecuted(
                new ProgrammingExecutedEventArgs { Success = false, Error = exception.InnerExceptions[0] });
            this.Explanation = "An error occurrred during the programming.";
        }
        // Stop execution of further taks
        this.cancellationTokenSource.Cancel();
    }

    private void ProgramImageAsyncDone()
    {
        this.OnProgrammingExecuted(new ProgrammingExecutedEventArgs { Success = true });
        this.Explanation = ResourceGeneral.PressNextBtn_Explanation;
        this.IsStepComplete = true;
    }

事件OnProgrammingStarted显示UI线程上的加载框。事件OnProgrammingExecuted会停止此加载框，并显示编程是否已成功完成的消息。两者都将UI线程作为订阅者。

Answer 1

我也在 Code Review 上提出了这个问题，因为这里并不是正确的地方。对于那些偶然发现这个问题并希望知道答案的人：you can find it here

任务：例外和取消

1 个答案: