How to properly cancel a BackgroundWorker

Question

I've got a GUI form which is acting as the main thread, while I've got a different class for the actual work which is needed to be done.

Is there a way to properly check the CancellationPending property of the worker since it's being activated from a different class, other than passing the worker as a parameter for the "DoJob" method so it could check the property?

The code (in the main class):

// This method is registered as the DoWork method for the worker
private void BackgroundWorker_DoWork(object sender, DoWorkEventArgs e)
{
    workClassInstance.DoJob();
}

private void buttonCancel_Click(object sender, RoutedEventArgs e)
{
    if (bw.WorkerSupportsCancellation == true)
    {
        bw.CancelAsync();
    }
}

Answer 1

Not really; you pretty much need to check the IsCancelled property of the BGW periodically to properly cancel. If it's important that a given operation explicitly not know about the BGW then there are a few options.

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One thing you can do if it's really important to not expose the BGW is to use a CancellationToken instead. You can create a CancellationTokenSource and expose it to whatever is responsible for canceling the task, and then pass the Token value of the cts to whatever is responsible for being canceled.

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Another option is that you could pass a Func<bool> as a parameter to DoJob. That function, when invoked, would return whether or not the task has currently requested cancellation. You would then call it like so:

workClassInstance.DoJob(()=> worker.CancellationPending);

You've now "hidden" the background worker from the workClassInstance and only exposed that aspect of its functionality that it needs, namely whether or not cancellation has been requested.