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我們知道 可以使用linq的 AsParallel()啟用平行作業（Plinq)，系統會自動啟用一定數量的線程去執行相應操作。它適用于有延時作業的操作。但記住：對于沒有延時操作的作業，還是老老實實用AsEnumrable()吧，因為線程 的分配，啟動，回收等反而增加了執行時間和資源。

例子1：平行作業。要注意 每次執行平行作業可能不會按順序

private void button7_Click(object sender, EventArgs e)        {
               Stopwatch sw = Stopwatch.StartNew();            Console.WriteLine("begin");             var query =   Enumerable.Range(1, 10).AsParallel().Select(o => {
    //平行作業                 //Console.WriteLine("作業 " + o.ToString ());                 Thread.Sleep(1000); //模擬延時事件                 return o;              }           ).ToArray ();            Console.WriteLine("end");            Console.WriteLine("times:" + sw.ElapsedMilliseconds.ToString());        }

看下結果，耗時2秒多，開了8個線程 。

begin

end times:2165 The thread 0x48e0 has exited with code 0 (0x0). The thread 0x551c has exited with code 0 (0x0). The thread 0x4378 has exited with code 0 (0x0). The thread 0x4668 has exited with code 0 (0x0). The thread 0x474c has exited with code 0 (0x0). The thread 0x3634 has exited with code 0 (0x0). The thread 0x419c has exited with code 0 (0x0). The thread 0x57a0 has exited with code 0 (0x0).

例子2，不使用平行作業

private void button7_Click(object sender, EventArgs e)        {
               Stopwatch sw = Stopwatch.StartNew();            Console.WriteLine("begin");             var query =   Enumerable.Range(1, 10).AsEnumerable().Select(o => {
    //平行作業                // Console.WriteLine("作業 " + o.ToString ());                 Thread.Sleep(1000); //模擬延時事件                 return o;              }           ).ToArray ();            Console.WriteLine("end");            Console.WriteLine("times:" + sw.ElapsedMilliseconds.ToString());        }

結果耗時 10秒

begin end times:10018

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