int i = 0;
int j = 0;
//前面是輔助(也就是所謂的工作者)線程，后面是I/O線程
ThreadPool.GetMaxThreads(out i, out j);
Console.WriteLine(i.ToString() + "   " + j.ToString()); //默認都是1000

//獲取空閑線程，由于現在沒有使用異步線程，所以為空
ThreadPool.GetAvailableThreads(out i, out j);
Console.WriteLine(i.ToString() + "   " + j.ToString()); //默認都是1000

public static bool QueueUserWorkItem (System.Threading.WaitCallback callBack, object state);

static void Main(string[] args)
 {
     Person p = new Person(1, "劉備");
     //啟動工作者線程
    ThreadPool.QueueUserWorkItem(new WaitCallback(RunWorkerThread), p);
 }

static void RunWorkerThread(object obj)
 {
     Thread.Sleep(200);
     Console.WriteLine("線程池線程開始!");
     Person p = obj as Person;
     Console.WriteLine(p.Name);
 }


 public class Person
 {
     public Person(int id, string name) { Id = id; Name = name; }
     public int Id { get; set; }
     public string Name { get; set; }
 }

public static System.Threading.RegisteredWaitHandle RegisterWaitForSingleObject (System.Threading.WaitHandle waitObject, System.Threading.WaitOrTimerCallback callBack, object state, int millisecondsTimeOutInterval, bool executeOnlyOnce);

// TaskInfo contains data that will be passed to the callback method.
public class TaskInfo
{
    public RegisteredWaitHandle Handle = null;
    public string OtherInfo = "default";
}


public static void Main(string[] args)
{
    // 主線程使用AutoResetEvent來給已注冊的等待句柄發信號, 此等待句柄執行回調方法
    AutoResetEvent ev = new AutoResetEvent(false);

    TaskInfo ti = new TaskInfo();
    ti.OtherInfo = "First task";
    // The TaskInfo for the task includes the registered wait handle returned by RegisterWaitForSingleObject.  This
    // allows the wait to be terminated when the object has been signaled once (see WaitProc).
    ti.Handle = ThreadPool.RegisterWaitForSingleObject(
        ev,
        new WaitOrTimerCallback(WaitProc),
        ti,
        1000,
        false
    );

    // 主線程等待三秒,為了演示隊列中的線程超時，然后發信號.
    Thread.Sleep(3100);
    Console.WriteLine("Main thread signals.");
    ev.Set();//發信號

    // The main thread sleeps, which should give the callback method time to execute.  If you comment out this line, the program usually ends before the ThreadPool thread can execute.
    Thread.Sleep(1000);
    // If you start a thread yourself, you can wait for it to end by calling Thread.Join.  This option is not available with  thread pool threads.
}

//The callback method executes when the registered wait times out, 
//or when the WaitHandle (in this case AutoResetEvent) is signaled. 
//WaitProc unregisters the WaitHandle the first time the event is  signaled.
public static void WaitProc(object state, bool timedOut)
{
    TaskInfo ti = (TaskInfo)state;

    string cause = "TIMED OUT";
    if (!timedOut) //如果Timeout為false，表示接收到的信號后執行的
    {
        cause = "SIGNALED";
        //如果回調方法執行的話是因為WaitHandle觸發信號的話，則用反注冊等待句柄來取消回調方法將來的執行。
        if (ti.Handle != null)
            ti.Handle.Unregister(null);//
    }

    Console.WriteLine("WaitProc( {0} ) executes on thread {1}; cause = {2}.",
        ti.OtherInfo, Thread.CurrentThread.GetHashCode().ToString(), cause);//超時后執行的
}