CODEWITHSUNDEEP
c#wpfasynchronousasync-await
avechuche
avechuche

Reputation: 1560

Task.WaitAll with CancelationToken

I need to execute many methods at the same time and the result of all, concatenate them in a single list. In the following example, I wait 3 seconds for each method, but in one of them I added a sleep (10 seconds) to check the result and it is not the expected one. The method never cancels and waits for those 10 seconds. What is the problem? Thank you!

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>();
}

Upvotes: 1

Views: 176

Answers (1)

Max
Max

Reputation: 7090

You must pass the CancellationToken to the methods and check if cancellationToken is requested or directly raise an exception.

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>();
}

See this question

Upvotes: 2

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