重做 EventWaitHandle 以异步等待信号

Question

当调用 EventWaitHandle.WaitOne 时，我需要更改当前代码以不阻塞当前线程。问题是我正在等待系统范围的事件。我还没有找到合适的替代品。

代码：

EventWaitHandle handle = new EventWaitHandle(false, EventResetMode.AutoReset, "Local event", out screenLoadedSignalMutexWasCreated);

        StartOtherApp();

        if (screenLoadedSignalMutexWasCreated)
        {
            isOtherAppFullyLoaded = handle.WaitOne(45000, true);

            if (isOtherAppFullyLoaded )
            {
                // do stuff
            }
            else
            {
                // do stuff
            }

            handle.Dispose();
            signalingCompleted = true;
        }
        else
        {
            isOtherAppFullyLoaded = false;
            throw new Exception(" ");
        }

我需要应用程序继续运行，而不是在我调用 WaitOne 的线路上停止，理想情况下会有等待。我该如何实现呢？

Answer 1

你可以使用AsyncFactory.FromWaitHandle，在我的AsyncEx library：

isOtherAppFullyLoaded = await AsyncFactory.FromWaitHandle(handle,
    TimeSpan.FromMilliseconds(45000));

实现使用ThreadPool.RegisterWaitForSingleObject:

public static Task<bool> FromWaitHandle(WaitHandle handle, TimeSpan timeout)
{
    // Handle synchronous cases.
    var alreadySignalled = handle.WaitOne(0);
    if (alreadySignalled)
        return Task.FromResult(true);
    if (timeout == TimeSpan.Zero)
        return Task.FromResult(false);

    // Register all asynchronous cases.
    var tcs = new TaskCompletionSource<bool>();
    var threadPoolRegistration = ThreadPool.RegisterWaitForSingleObject(handle,
        (state, timedOut) => ((TaskCompletionSource<bool>)state).TrySetResult(!timedOut),
        tcs, timeout);
    tcs.Task.ContinueWith(_ =>
    {
        threadPoolRegistration.Dispose();
    }, TaskScheduler.Default);
    return tcs.Task;
}