线程化多个异步调用

看看这个例子:

关键的是,等待自动resetEvents发生在后台线程中。

public partial class MainPage : UserControl
{
    public MainPage()
    {
        InitializeComponent();

        Completed += (s, a) => { Debug.WriteLine("done"); };

        wrk.DoWork += (s, a) =>
            {
                Start();
            };

        wrk.RunWorkerAsync();
    }
    public event EventHandler Completed;

    private void Start()
    {
        auto1.WaitOne();
        auto2.WaitOne();

        Completed(this, EventArgs.Empty);
    }

    public AutoResetEvent auto1 = new AutoResetEvent(false);
    public AutoResetEvent auto2 = new AutoResetEvent(false);

    BackgroundWorker wrk = new BackgroundWorker();

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        ServiceReference1.Service1Client clien = new SilverlightAsyncTest.ServiceReference1.Service1Client();

        clien.DoWorkCompleted += new EventHandler<SilverlightAsyncTest.ServiceReference1.DoWorkCompletedEventArgs>(clien_DoWorkCompleted);
        clien.DoWork2Completed += new EventHandler<SilverlightAsyncTest.ServiceReference1.DoWork2CompletedEventArgs>(clien_DoWork2Completed);

        clien.DoWorkAsync();
        clien.DoWork2Async();
    }

    void clien_DoWork2Completed(object sender, SilverlightAsyncTest.ServiceReference1.DoWork2CompletedEventArgs e)
    {
        Debug.WriteLine("2");
        auto1.Set();
    }

    void clien_DoWorkCompleted(object sender, SilverlightAsyncTest.ServiceReference1.DoWorkCompletedEventArgs e)
    {
        Debug.WriteLine("1");
        auto2.Set();
    }
}

可以使用每个异步方法返回的IAsyncResult中的WaitHandle来完成。

代码很简单。在Silverlight中,我只做了10次服务调用,将一个项目添加到列表框中。我将等到所有服务调用结束后再向列表中添加另一条消息(这必须在不同的线程中运行,以避免阻塞UI)。还要注意,向列表中添加项目必须通过Dispatcher完成,因为它们将修改UI。有很多lamda,但很容易理解。

 public MainPage()
        {
            InitializeComponent();
            var results = new ObservableCollection<string>();
            var asyncResults = new List<IAsyncResult>();
            resultsList.ItemsSource = results;
            var service = new Service1Client() as Service1;

            1.To(10).Do(i=>
                asyncResults.Add(service.BeginDoWork(ar =>
                    Dispatcher.BeginInvoke(() => results.Add(String.Format("Call {0} finished: {1}", i, service.EndDoWork(ar)))),
                    null))
            );

            new Thread(()=>
            {
                asyncResults.ForEach(a => a.AsyncWaitHandle.WaitOne());
                Dispatcher.BeginInvoke(() => results.Add("Everything finished"));
            }).Start();
        }

public class Service1
    {
        private const int maxMilliSecs = 500;
        private const int minMillisSecs = 100;
        [OperationContract]
        public int DoWork()
        {
            int millisSecsToWait = new Random().Next(maxMilliSecs - minMillisSecs) + minMillisSecs;
            Thread.Sleep(millisSecsToWait);
            return millisSecsToWait;
        }
    }