Question

There is a scenario in which a user terminates the application, while it is still processing data via BackgroundWorker.
I would like to send cancel or terminate command to this method. I tried calling CancelAsync() method, but it obviously didn’t work the way I expected and the worker still continued processing.
What is a good way to signal the BackgroundWorker, and especially its RunWorkerCompleted method to stop processing?
Do I have to use state variables?

Answer 1

This is the code executed when you call CancelAsync() on a BackgroundWorker

public void CancelAsync()
{
    if (!this.WorkerSupportsCancellation)
    {
        throw new InvalidOperationException(SR.GetString
                 ("BackgroundWorker_WorkerDoesntSupportCancellation"));
    }
    this.cancellationPending = true;
}

As you can see, they set the internal cancellationPending variable to true after checking the value of WorkerSupportsCancellation.

So you need to set WorkerSupportsCancellation = true;, when you exit from your app call backGroundWorkerInstance.CancelAsync() and inside the DoWork or RunWorkerCompleted test the CancellationPending. If it’s true stop your process.