Task启动方式及源码探究

        static void Main(string[] args)
        {
            for (int i = 0; i < 5; i++)
            {
                 Task.Run(() => Sayhi("task"));
                 new TaskFactory().StartNew(() => Sayhi("taskfactory"));
            }
        
            Console.ReadLine();
        } 


        public static void Sayhi(string method)
        {
            Console.WriteLine(method+":"+Thread.CurrentThread.ManagedThreadId);
        }

 new TaskFactory().StartNew(() => Sayhi("taskfactory"),TaskCreationOptions.LongRunning);

public static Task Run(Action action)
        {
            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
            return Task.InternalStartNew(null, action, null, default(CancellationToken), TaskScheduler.Default, 

TaskCreationOptions.DenyChildAttach, InternalTaskOptions.None, ref stackMark); }

   public Task StartNew(Action action)
        {
            StackCrawlMark stackMark = StackCrawlMark.LookForMyCaller;
            Task currTask = Task.InternalCurrent;
            return Task.InternalStartNew(currTask, action, null, m_defaultCancellationToken, GetDefaultScheduler(currTask),
                m_defaultCreationOptions, InternalTaskOptions.None, ref stackMark);
        }

 internal void ScheduleAndStart(bool needsProtection)
        { 
            try
            {
                // Queue to the indicated scheduler.
                m_taskScheduler.InternalQueueTask(this); //调度任务
            }
            catch (ThreadAbortException tae)
            {
                AddException(tae);
                FinishThreadAbortedTask(true, false);
            }
       }

m_taskScheduler实例就是上面的TaskScheduler.Default,来瞧瞧是装了什么东西

 private static readonly TaskScheduler s_defaultTaskScheduler = new ThreadPoolTaskScheduler();

 public static TaskScheduler Default 
        {
            get
            {
                return s_defaultTaskScheduler;
            }
        }

ThreadPoolTaskScheduler，瞧瞧这单词是不是有内味了，来，答案快水落石出了。

   protected internal override void QueueTask(Task task)
        {
            if ((task.Options & TaskCreationOptions.LongRunning) != 0)
            {
                // Run LongRunning tasks on their own dedicated thread.
                Thread thread = new Thread(s_longRunningThreadWork);
                thread.IsBackground = true; // Keep this thread from blocking process shutdown
                thread.Start(task);
            }
            else
            {
                // Normal handling for non-LongRunning tasks.
                bool forceToGlobalQueue = ((task.Options & TaskCreationOptions.PreferFairness) != 0);
                ThreadPool.UnsafeQueueCustomWorkItem(task, forceToGlobalQueue);  
            }
        }