Stopping a task without a CancellationToken

Question

I am using an external library that has async methods, but not CancellationToken overloads.

Now currently I am using an extension method fr

Answer 1

As you suggest you can cancel a task by passing in a CancellationToken and then calling Cancel.

As for how you'd go about triggering that cancellation depends on the nature of your application.

A few possible scenarios

1. Carry on until you click cancel
2. Cancel after a fixed time
3. Cancel if there's been no progress for a fixed time

In case 1 you simply cancel the task from your cancel button, for example

private void cancel_Click(object sender, RoutedEventArgs e)
{
    ...
    cts = new CancellationTokenSource();
    await MyAsyncTask(cts.Token);
    cts.Cancel();
    ...
}

In case 2 you could start a timer when you start your task and then cancel the task after a set time using CancelAfter, for example

private void start_Click(object sender, RoutedEventArgs e)
{
    ...
    cts = new CancellationTokenSource();
    cts.CancelAfter(30000);
    await MyAsyncTask(cts.Token);
    ...
}

In case 3 you could do something with progress, for example

private void start_Click(object sender, RoutedEventArgs e)
{
    ...
    Progress progressIndicator = new Progress(ReportProgress);
    cts = new CancellationTokenSource();
    await MyAsyncTask(progressIndicator, cts.Token);
    ...
}

void ReportProgress(int value)
{
    // Cancel if no progress
}

Here are a few useful links Parallel programming, task cancellation, progress and cancellation, cancel tasks after set time, and cancel a list of tasks.