Using CancellationToken for timeout in Task.Run does not work [duplicate]

Answer 1

I think because you're not invoking the method ThrowIfCancellationRequested() from your CancellationToken object. You're ignoring, in this way, the request for the cancellation of the task.

You should do something like this:

void Main()
{
    var ct = new CancellationTokenSource(500).Token;
     var v = 
     Task.Run(() =>
    {
        Thread.Sleep(1000);
        ct.ThrowIfCancellationRequested();
        return 10;
    }, ct).Result;

    Console.WriteLine(v); //now a TaskCanceledException is thrown.
    Console.Read();
}

The second variant of your code works, because you're already initializing a token with a Canceled state set to true. Indeed, as stated here:

If canceled is true, both CanBeCanceled and IsCancellationRequested will be true

the cancellation has already been requested and then the exception TaskCanceledException will be immediately thrown, without actually starting the task.