C# 多线程编程 - 线程池

常用技术

线程池中调用委托
向线程池中放入异步操作
线程池与并行度
实现一个取消选项
线程池中使用等待事件处理器和超时
计时器
BackgroundWorker组件

线程池中的工作线程都是后台线程
保持线程中的操作都是短暂的

异步编程模型

private delegate string RunOnThreadPool(out int threadId);

private static void CallBack(IAsyncResult ar) {
    Console.WriteLine("\nstarting a callback ...");
    Console.WriteLine("state passed to a callback: {0}", ar.AsyncState);
    Console.WriteLine("CallBack is threadpool thread: {0}", Thread.CurrentThread.IsThreadPoolThread);
    Console.WriteLine("CallBack ThreadPool worker thread id: {0}", 
	Thread.CurrentThread.ManagedThreadId);
}
private static string Test(out int threadId) {
    Console.WriteLine("\nTest Starting ...");
    Console.WriteLine("Test is threadpool thread: {0}", Thread.CurrentThread.IsThreadPoolThread);
    Thread.Sleep(2000);
    threadId = Thread.CurrentThread.ManagedThreadId;
    return string.Format("Test ThreadPool worker thread id: {0}", threadId);
}

public static void TestPoolDelegate() {
    int threadId = 0;
    RunOnThreadPool poolDelegate = Test;

    Thread t = new Thread(() => Test(out threadId));
    t.Start();
    t.Join();

    Console.WriteLine("TestPoolDelegate ThreadId: {0}", threadId);
	
    // 异步编程模型 APM，推荐使用任务并行库 TPL
    IAsyncResult r = poolDelegate.BeginInvoke(out threadId, CallBack, "a delegate asynchronous call");
    r.AsyncWaitHandle.WaitOne();
    string result = poolDelegate.EndInvoke(out threadId, r);
    // *****************************************************
    
    Console.WriteLine("TestPoolDelegate ThreadPool worker thread id: {0}", threadId);
    Console.WriteLine(result);

    Thread.Sleep(2000);
}

向线程池中放入异步操作

private static void AsyncOperation(object state) {
    Console.WriteLine("\n******************************************\n状态: {0}", state ?? "(null)");
    Console.WriteLine("Worker thread id: {0}", Thread.CurrentThread.ManagedThreadId);
    Thread.Sleep(2000);
}
public static void TestPoolAsync() {
    const int x = 1;
    const int y = 2;

    const string lambdaState = "state 2";

    ThreadPool.QueueUserWorkItem(AsyncOperation, "async state");
    Thread.Sleep(1000);

    ThreadPool.QueueUserWorkItem(state =>
    {
        Console.WriteLine("\nOperation state: {0}", state);
        Console.WriteLine("Worker Thread id: {0}", Thread.CurrentThread.ManagedThreadId);

        Thread.Sleep(5000);
    }, "lambda state");

    ThreadPool.QueueUserWorkItem(_ =>
    {
        Console.WriteLine("\nOperation state: {0}, {1}", x + y, lambdaState);
        Console.WriteLine("********** Worker Thread id: {0}", Thread.CurrentThread.ManagedThreadId);

        Thread.Sleep(10000);
    }, "lambda _");
    
    Thread.Sleep(2000);
}