Using CancellationToken for timeout in Task.Run does not work

Question

OK, my questions is really simple. Why this code does not throw TaskCancelledException?

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

    Console.WriteLine(v); // this outputs 10 - instead of throwing error.
    Console.Read();
}

But this one works

static void Main()
{
    var v = Task.Run(() =>
    {
        Thread.Sleep(1000);
        return 10;
    }, new CancellationToken(true).Token).Result;

    Console.WriteLine(v); // this one throws
    Console.Read();
}

Answer 1

Cancellation in Managed Threads:

Cancellation is cooperative and is not forced on the listener. The listener determines how to gracefully terminate in response to a cancellation request.

You didn't write any code inside your Task.Run method to access your CancellationToken and to implement cancellation - so you effectively ignored the request for cancellation and ran to completion.