为什么Task.IsCanceled不是真的？

Question

我这里有一个简单的程序

private static void CancellingSingleTask()
{
    DateTime whenStarted = DateTime.Now;

    Console.WriteLine("[{0}] - Main: Started", TimeSpan.FromTicks(DateTime.Now.Ticks - whenStarted.Ticks));

    CancellationTokenSource cts = new CancellationTokenSource();
    CancellationToken ct = cts.Token;

    Task task = Task.Factory.StartNew(() => 
    {
        int? taskId = Task.CurrentId;

        Console.WriteLine("[{0}] - Task - [{1}]:  Started", TimeSpan.FromTicks(DateTime.Now.Ticks - whenStarted.Ticks), taskId);

        Thread.Sleep(2000);

        if (ct.IsCancellationRequested)
        {
            Console.WriteLine("[{0}] - Task - [{1}]:  Cancellation Requested", TimeSpan.FromTicks(DateTime.Now.Ticks - whenStarted.Ticks), taskId);
            throw new OperationCanceledException();
        }
        Console.WriteLine("[{0}] - Task - [{1}]:  No Cancellation Requested", TimeSpan.FromTicks(DateTime.Now.Ticks - whenStarted.Ticks), taskId);
    }, ct);

    Action Print = () =>
    {
        Console.WriteLine("[{0}] - Main: Task.IsCanceled = [{1}]  Task.IsFaulted = [{2}] Task.IsCompleted = [{3}] Task.Status = [{4}]", TimeSpan.FromTicks(DateTime.Now.Ticks - whenStarted.Ticks),
            task.IsCanceled, task.IsFaulted, task.IsCompleted, task.Status);
    };

    Console.WriteLine("[{0}] - Main: Started New Task", TimeSpan.FromTicks(DateTime.Now.Ticks - whenStarted.Ticks));
    Print();

    Thread.Sleep(1000);

    Console.WriteLine("[{0}] - Main: Cancelling Task", TimeSpan.FromTicks(DateTime.Now.Ticks - whenStarted.Ticks));

    cts.Cancel();

    Thread.Sleep(2000);

    Console.WriteLine("[{0}] - Main: After Cancelling Task", TimeSpan.FromTicks(DateTime.Now.Ticks - whenStarted.Ticks));
    Print();

    try
    {
        Console.WriteLine("[{0}] - Main: Waiting For Task", TimeSpan.FromTicks(DateTime.Now.Ticks - whenStarted.Ticks));

        task.Wait();

        Console.WriteLine("[{0}] - Main: After Waiting For Task", TimeSpan.FromTicks(DateTime.Now.Ticks - whenStarted.Ticks));
        Print();
    }
    catch (AggregateException aggregateException)
    {
        Thread.Sleep(2000);
        Console.WriteLine("[{0}] - Main: In Catch Block", TimeSpan.FromTicks(DateTime.Now.Ticks - whenStarted.Ticks));
        Print();

        foreach (var exception in aggregateException.InnerExceptions)
        {
            Console.WriteLine("[{0}] - Main: Received Exception In Task [{1}]", TimeSpan.FromTicks(DateTime.Now.Ticks - whenStarted.Ticks), exception.Message);
        }
    }

} 

样本输出
[00：00：00.0010000]-主程序：已启动
[00：00：00.0040002]-主要：已开始新任务
[00：00：00.0060003]-Main：IsCanceled = [False] IsFaulted = [False] IsCompleted = [False]状态= [Running]
[00：00：00.0070004]-任务-[1]：已开始
[00：00：01.0070576]-主程序：取消任务
[00：00：02.0071148]-任务-[1]：请求取消
[00：00：03.0111722]-主程序：取消任务后
[00：00：03.0111722]-Main：IsCanceled = [False] IsFaulted = [True] IsCompleted = [True] Status = [Faulted]
[00：00：03.0111722]-主程序：等待任务
[00：00：05.0112866]-主要：在接球区
[00：00：05.0112866]-Main：IsCanceled = [False] IsFaulted = [True] IsCompleted = [True] Status = [Faulted]
[00：00：05.0112866]-主操作：任务中收到异常[操作已取消。

我从没看到Task.IsCanceled设置为true，是我犯了一个错误还是遗漏了一些明显的东西。 我已经对此问题进行了一些研究/搜索，但是找不到最终的答案。

注意：有关StackOverFlow的相关问题取消任务 任务IsCanceled为false，而我取消了 Task.IsCancelled则不起作用

Answer 1

我想您应该将CancellationToken传递给OperationCanceledException的构造函数。

  if (ct.IsCancellationRequested)
    {
        Console.WriteLine("[{0}] - Task - [{1}]:  Cancellation Requested", TimeSpan.FromTicks(DateTime.Now.Ticks - whenStarted.Ticks), taskId);
        throw new OperationCanceledException(ct);
    }

TPL将检查两个CancellationToken是否相同，如果是这样，它将在您的情况下将其标记为“ Cancelled ，因此TPL假定您的任务未取消。

甚至更好地使用ThrowIfCancellationRequested方法，就像那样简单

ct.ThrowIfCancellationRequested();