C# 多线程 04-使用任务平行库 06-实现取消选项

🏷️ 《C# 多线程》

实现取消选项

本节是 Task 中实现取消选项，同使用线程池中实现取消是一样的。(参照：C# 多线程 03-使用线程池 04-实现一个取消选项)

/// <summary>
/// 实现取消选项
/// </summary>
/// <param name="args"></param>
static void Main(string[] args)
{
    var cts = new CancellationTokenSource();
    var longTask = new Task<int>(() => TaskMethod("Task 1", 10, cts.Token));
    Console.WriteLine(longTask.Status); // Created
    cts.Cancel();
    Console.WriteLine(longTask.Status); // Created
    Console.WriteLine($"First task has benn cancelled before execution");

    cts = new CancellationTokenSource();
    longTask = new Task<int>(() => TaskMethod("Task 2", 10, cts.Token));
    longTask.Start();
    for (int i = 0; i < 5; i++)
    {
        Thread.Sleep(TimeSpan.FromSeconds(0.5));
        Console.WriteLine(longTask.Status); // Running
    }
    cts.Cancel();
    for (int i = 0; i < 5; i++)
    {
        Thread.Sleep(TimeSpan.FromSeconds(0.5));
        Console.WriteLine(longTask.Status); // RanToCompletion
    }

    Console.WriteLine($"A task has been completed with result {longTask.Result}"); // -1
    Console.ReadLine();
}

static int TaskMethod(string name, int seconds, CancellationToken token)
{
    Console.WriteLine($"Task {name} is running on a thread id : {Thread.CurrentThread.ManagedThreadId}. " +
        $"Is thread pool thread: {Thread.CurrentThread.IsThreadPoolThread}");
    for (int i = 0; i < seconds; i++)
    {
        Thread.Sleep(TimeSpan.FromSeconds(1));
        if (token.IsCancellationRequested)
        {
            return -1;
        }
    }
    return 42 * seconds;
}

打印结果

Created
Created
First task has benn cancelled before execution
Task Task 2 is running on a thread id : 3. Is thread pool thread: True
Running
Running
Running
Running
Running
Running
RanToCompletion
RanToCompletion
RanToCompletion
RanToCompletion
A task has been completed with result -1