优先线程未按预期顺序完成工作

Question

在学校，我被分配了一个任务来构建一个简单的应用程序来展示线程如何优先处理工作。问题是我触发的线程不会坚持设置和随机完成的优先级（或者看起来像这样）。

这是我的主窗口的代码：

namespace ThreadsShowtime
{
    public partial class MainWindow : Window
    {
        private SuperThread _lowest;
        private SuperThread _below;
        private SuperThread _normal;
        private SuperThread _above;
        private SuperThread _highest;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void ButtonClick(object sender, RoutedEventArgs e)
        {
            _lowest = new SuperThread(ThreadPriority.Lowest, elipseLowest, Dispatcher, lowestLbl);
            _below = new SuperThread(ThreadPriority.BelowNormal, elipseBelow, Dispatcher, belowLbl);
            _normal = new SuperThread(ThreadPriority.Normal, elipseNormal, Dispatcher, normalLbl);
            _above = new SuperThread(ThreadPriority.AboveNormal, elipseAbove, Dispatcher, aboveLbl);
            _highest = new SuperThread(ThreadPriority.Highest, elipseHighest, Dispatcher, highestLbl);

            _lowest.Start();
            _below.Start();
            _normal.Start();
            _above.Start();
            _highest.Start();
        }
    }
}

以及SuperThread类代码：

namespace ThreadsShowtime
{
    public class SuperThread
    {
        private readonly Stopwatch _stopwatch;
        public readonly Thread Thread;

        public SuperThread(ThreadPriority thp, Shape sh, Dispatcher dispatcher, ContentControl lbl)
        {
            Thread = new Thread(() => DummyMethod(dispatcher, sh, lbl)) {Priority = thp};
            _stopwatch = new Stopwatch();
        }

        public long Elapsed { get; private set; }
        public double ElapsedSeconds => Elapsed / 1000.0;


        private void DummyMethod(Dispatcher dispatcher, Shape sh, ContentControl lbl)
        {
            _stopwatch.Start();
            dispatcher.Invoke(() =>
            {
                sh.Fill = Brushes.GreenYellow;
            }, DispatcherPriority.Normal);    

            for (var idx = 0; idx < 30000; idx++) Console.WriteLine(idx);

            dispatcher.Invoke(() =>
            {
                sh.Fill = Brushes.OrangeRed;
            }, DispatcherPriority.Normal);

            _stopwatch.Stop();
            Elapsed = _stopwatch.ElapsedMilliseconds;

            dispatcher.Invoke(() =>
            {
                lbl.Content = ElapsedSeconds;
            }, DispatcherPriority.ContextIdle);

        }

        public void Start()
        {
            Thread.Start();
        }
    }
}

此应用程序的输出如下所示：

为什么会这样？ 非常感谢您提供的任何帮助。

Answer 1

由于dispatcher.Invoke() 和Console.WriteLine()，您的代码实际上是单线程的。您看到的是排队线程的稍微不可预测的结果。这些队列不是 FIFO。

要查看正确的效果，请对一些纯粹受 CPU 限制的代码进行基准测试，例如 Sort()。确保它们运行 > 200 毫秒，较小的运行是没有意义的。