Task.WaitAll with CancellationToken

Question

我需要同时执行许多方法和结果，将它们连接在一个列表中。在下面的示例中，我为每个方法等待3秒，但在其中一个方法中，我添加了一个睡眠（10秒）来检查结果，这不是预期的结果。该方法永远不会取消并等待那10秒钟。问题是什么？谢谢！

var result = await Task.Run(() => Load<MyCustomClass>(OneMethod(), OtherMethod()));

private List<T> OneMethod()
{
    return new List<T>();
}

private List<T> OtherMethod()
{
    Thread.Sleep(10000);

    return new List<T>();
}

private async Task<List<T>> Load<T>(params List<T>[] taskList)
{
    try
    {
        return (await Task.WhenAll(taskList.Select(x =>
            Task.Run(() => x, new CancellationTokenSource(3000).Token)))).SelectMany(x => x).ToList();
    }
    catch (Exception currentException)
    {
        //BLA BLA BLA
    }

    return new List<T>();
}

Answer 1

您必须将CancellationToken传递给方法并检查是否请求了cancellationToken，或者直接引发异常。

var t = new CancellationTokenSource(3000).Token
var result = await Task.Run(() => Load<MyCustomClass>(OneMethod(t), OtherMethod(t)));

private List<T> OneMethod(CancellationToken t)
{
    token.ThrowIfCancellationRequested();
    return new List<T>();
}

private List<T> OtherMethod(CancellationToken t)
{
    Thread.Sleep(10000);
    token.ThrowIfCancellationRequested();
    // or you can check if cancellation is requested
    // if (token.IsCancellationRequested) ...
    return new List<T>();
}

private async Task<List<T>> Load<T>(params List<T>[] taskList)
{
    try
    {
        return (await Task.WhenAll(taskList.Select(x =>
            Task.Run(() => x)))).SelectMany(x => x).ToList();
    }
    catch (Exception currentException)
    {
        //BLA BLA BLA
    }

    return new List<T>();
}

见this question