CODEWITHSUNDEEP
c#task-parallel-library
Teddy Bo
Teddy Bo

Reputation: 679

How not to continue a cancelled task?

Here is a sample code:

var task = Task.Factory.StartNew(() => { throw new Exception(); });
task.ContinueWith(t => Console.WriteLine("Exception"), TaskContinuationOptions.OnlyOnFaulted);
task.ContinueWith(t => Console.WriteLine("Success"), TaskContinuationOptions.NotOnFaulted)
    .ContinueWith(t => Console.WriteLine("Should not be executed. Task status = " + t.Status, TaskContinuationOptions.NotOnCanceled));
Console.ReadLine();

The output is (the order does not matter):

Exception

Should not be executed. Task status = Canceled

Why was the second ContinueWith executed and how to prevent it?

Upvotes: 4

Views: 555

Answers (2)

Ilya Kozhevnikov
Ilya Kozhevnikov

Reputation: 10432

Because typo, Ctrl+Shift+F1 it.

// ContinueWith([NotNull] Action<Task> continuationAction)
// WriteLine([NotNull] string format, object arg0)
.ContinueWith(t => Console.WriteLine("Should not be executed. Task status = " + t.Status, TaskContinuationOptions.NotOnCanceled));

// ContinueWith([NotNull] Action<Task> continuationAction, TaskContinuationOptions continuationOptions)
// WriteLine(string value) 
.ContinueWith(t => Console.WriteLine("Should not be executed. Task status = " + t.Status), TaskContinuationOptions.NotOnCanceled);

Upvotes: 1

Timothy Shields
Timothy Shields

Reputation: 79601

The parentheses in your last call to ContinueWith are wrong:

.ContinueWith(t =>
    Console.WriteLine(
        "Should not be executed. Task status = " + t.Status,
        TaskContinuationOptions.NotOnCanceled));

TaskContinuationOptions.NotOnCanceled is being passed as an argument to WriteLine.

Fixed:

.ContinueWith(t =>
    Console.WriteLine(
        "Should not be executed. Task status = " + t.Status),
    TaskContinuationOptions.NotOnCanceled);

Upvotes: 2

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