c#-等待完成2个线程中的1个

当我试图提醒主线程时,什么都没有发生。

这是因为主线程正在监视器上等待在此处创建的对象:

private static object _syncFinger = new object(); // used for syncing

但每个线程都会替换该对象值,然后向监视器发出信号 新 对象主线程不知道新对象,因此当然,向监视器发送新对象的信号对主线程没有影响。

首先,无论何时创建对象以用于 lock ,成功 readonly :

private static readonly object _syncFinger = new object(); // used for syncing

这始终是正确的做法,这将防止您在线程等待被监视对象时犯更改被监视对象的错误。

接下来,创建一个单独的字段来保存 WinBioIdentity 值,例如:

private static WinBioIdentity _syncIdentity;

和使用 那个 要将结果传回主线程,请执行以下操作:

private static bool AttemptIdentify()
{
    // waiting for either the user cancels or a finger is inserted
    lock (_syncFinger)
    {
        _syncIdentity = null;
        Thread tEscape = new Thread(new ThreadStart(HandleIdentifyEscape));
        Thread tIdentify = new Thread(new ThreadStart(HandleIdentify));
        tEscape.IsBackground = false;
        tIdentify.IsBackground = false;
        tEscape.Start();
        tIdentify.Start();
        Monitor.Wait(_syncFinger); // -> Wait part
    }

    // Checking the change in the locked object

    if (_syncIdentity != null) // checking for identity found
    {
        Console.WriteLine("Identity: {0}", ((FingerData)_syncIdentity).Guid.ToString());
        return true;
    }

    return false; // returns with no error
}

private static void HandleIdentifyEscape()
{
    do
    {
        Console.Write("Enter 'c' to cancel: ");
    } while (Console.ReadKey().Key != ConsoleKey.C);
    LockNotify((object)_syncFinger);
}

private static void HandleIdentify()
{
    WinBioIdentity temp = null;
    do
    {
        Console.WriteLine("Enter your finger.");
        try // trying to indentify
        {
            temp = Fingerprint.Identify(); // returns FingerData type
        }
        catch (Exception ex)
        {
            Console.WriteLine("ERROR: " + ex.Message);
        }
        // if couldn't identify, temp would stay null
        if(temp == null)
        {
            Console.Write("Invalid, ");
        }
    } while (temp == null);

    __syncIdentity = temp;
    LockNotify(_syncFinger);
}

尽管如此,你还是应该使用现代的 async / await 这方面的习惯用法:

private static bool AttemptIdentify()
{
    Task<WinBioIdentity> fingerTask = Task.Run(HandleIdentify);
    Task cancelTask = Task.Run(HandleIdentifyEscape);

    if (Task.WaitAny(fingerTask, cancelTask) == 0)
    {
        Console.WriteLine("Identity: {0}", fingerTask.Result.Guid);
        return true;
    }

    return false;
}

private static void HandleIdentifyEscape()
{
    do
    {
        Console.Write("Enter 'c' to cancel: ");
    } while (Console.ReadKey().Key != ConsoleKey.C);
}

private static WinBioIdentity HandleIdentify()
{
    WinBioIdentity temp = null;
    do
    {
        Console.WriteLine("Enter your finger.");
        try // trying to indentify
        {
            temp = Fingerprint.Identify(); // returns FingerData type
        }
        catch (Exception ex)
        {
            Console.WriteLine("ERROR: " + ex.Message);
        }
        // if couldn't identify, temp would stay null
        if(temp == null)
        {
            Console.Write("Invalid, ");
        }
    } while (temp == null);

    return temp;
}

以上只是一个简单的例子。最好是 AttemptIdentify() 方法 异步 本身,然后使用 await Task.WhenAny() 而不是 Task.WaitAny() . 最好包括一些中断任务的机制,也就是说,一旦一个任务完成,你应该想中断另一个任务,这样它就不会到处乱跑,继续尝试它的工作。

但这些问题并不是 异步 / 等候 版本,无需解决即可改进现有代码。