C# 调用委托线程BeginInvoke与EndInvoke

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本文详细介绍了如何在C#中使用异步回调和线程池，包括线程池的工作原理、如何创建线程池任务以及如何实现异步回调函数。通过实例演示了在异步操作中如何正确地利用线程池来提高程序的并发性和效率。

第一步，委托的申明

private delegate string RunOnThreadPool(out int threadId);

第二步，将被作为线程运行的函数

private static string Test(out int threadId)
{
    Console.WriteLine("starting...");
    Console.WriteLine("is thread pool thread: {0}", Thread.CurrentThread.IsThreadPoolThread);
    Thread.Sleep(TimeSpan.FromSeconds(2));
    threadId = Thread.CurrentThread.ManagedThreadId;
    return string.Format("thread pool worker thread id was:{0}", threadId);
}

第三步，回调函数

private static void Callback(IAsyncResult ar)
{
    Console.WriteLine("starting a callback...");
    Thread.Sleep(TimeSpan.FromSeconds(2));
    Console.WriteLine("starting passed to a callback:{0}", ar.AsyncState);
    Console.WriteLine("is thread pool thread: {0}", Thread.CurrentThread.IsThreadPoolThread);
    Console.WriteLine("thread pool worker thread id: {0}", Thread.CurrentThread.ManagedThreadId);
}

第四步，主函数

static void Main(string[] args)
{
    int threadId = 0;
    // 申明对函数的引用
    RunOnThreadPool poolDelegate = Test;
    var t = new Thread(() => Test(out threadId));
    t.Start();
    t.Join();
    Console.WriteLine("thread id: {0}", threadId);
    //回调函数在委托函数调用结束后开始
    IAsyncResult r = poolDelegate.BeginInvoke(out threadId, Callback, "a delegate asynchronous call");
    //等待，直到线程结束
    r.AsyncWaitHandle.WaitOne();
    //while(!r.AsyncWaitHandle.WaitOne(TimeSpan.FromSeconds(0.1)))
    //{
    //    Console.Write("*");
    //}
    //获取线程运行结束后的结果
    string result = poolDelegate.EndInvoke(out threadId, r);

    Console.WriteLine("thread pool worker thread id: {0}", threadId);

    Console.WriteLine(result);

    Thread.Sleep(TimeSpan.FromSeconds(2));

    Console.ReadKey();
}