#眉標=ThreadPool、foreach、Queue
#副標= .NET執行緒控制技巧
#大標=運用ThreadPool發揮CPU運算能力
#作者=文／圖 吳剛志
#引言=


==<box>===========
程式1	不使用多執行緒，直接以迴圈來處理每一個工作
private static void SingleThreadSample
	(string[] files)
{
    foreach (string file in files)
    {
        MakeThumb(file);
    }
}
==<end>==============




==<box>===========
程式2	
private static void MultiThreadSample1
	(string[] files)
{
    List<Thread> threads = new List<Thread>();

    foreach (string file in files)
    {
        Thread t = new Thread(_MTS1);
        threads.Add(t);
        t.Start(file);
    }
    foreach (Thread t in threads)
    {
        t.Join();
    }
}

private static void _MTS1(object state)
{
    MakeThumb(state as string);
}
==<end>==============



==<box>===========
程式3	
private static void MultiThreadSample2
	(string[] files, int threadCount)
{
    Queue<string> queue = 
		new Queue<string>(files);
    Thread[] threads = new Thread[threadCount];
    for (int pos = 0; 
		pos < threads.Length; 
		pos++)
    {
        threads[pos] = new Thread(_MTS2);
        threads[pos].Start(queue);
    }
    foreach (Thread t in threads)
    {
        t.Join();
    }
}

private static void _MTS2(object state)
{
    Queue<string> queue = (Queue<string>)state;
    while(true) {
        string file = null;
        lock (queue)
        {
            if (queue.Count == 0) break;
            file = queue.Dequeue();
        }
        MakeThumb(file);
    }
}
==<end>==============




==<box>===========
程式4	
private static void ThreadPoolSample
	(string[] files)
{
    List<WaitHandle> waits = 
		new List<WaitHandle>();
        foreach (string file in files)
    {
        WorkItem wi = new WorkItem(file);
        waits.Add(wi.wait);
        ThreadPool.QueueUserWorkItem(_WCB, wi);
    }
    foreach (WaitHandle wait in waits)
    {
        wait.WaitOne();
    }
}

private static void _WCB(object state)
{
    WorkItem wi = state as WorkItem;
    MakeThumb(wi.file);
    wi.wait.Set();
}

private class WorkItem
{
    public WorkItem(string _file)
    {
        this.file = _file;
    }
    public string file = null;
    public ManualResetEvent wait = 
		new ManualResetEvent(false);
}
==<end>==============