阻塞直到事件完成

Question

如何在异步事件完成之前阻塞？

这是一种阻塞直到事件被调用的方法，方法是在事件处理程序中设置一个标志并轮询该标志：

private object DoAsynchronousCallSynchronously()
{
    int completed = 0;
    AsynchronousObject obj = new AsynchronousObject();
    obj.OnCompletedCallback += delegate { Interlocked.Increment(ref completed); };
    obj.StartWork();

    // Busy loop
    while (completed == 0)
        Thread.Sleep(50);

    // StartWork() has completed at this point.
    return obj.Result;
}

有没有办法在没有轮询的情况下做到这一点？

Answer 1

    private object DoAsynchronousCallSynchronously()
    {
        AutoResetEvent are = new AutoResetEvent(false);
        AsynchronousObject obj = new AsynchronousObject();    
        obj.OnCompletedCallback += delegate 
        {
            are.Set();
        };    
        obj.StartWork();    

        are.WaitOne();
        // StartWork() has completed at this point.    
        return obj.Result;
    }

Answer 2

不使用异步操作？异步操作背后的重点不是阻塞调用线程。

如果您想在操作完成之前阻塞调用线程，请使用同步操作。