backgroundworker.cancelasync always busy

hello all,

I have a wpf project, and on the timeconsuming processing, I run the method on a background worker.  like so

        public InternalLoginClass()
        {
                                    if (!backgroundWorkerTimeline.IsBusy)
                                    {
                                        object[] tempArguments = new object[3];
                                        tempArguments[0] = connString;
                                        tempArguments[1] = "FULL";
                                        tempArguments[2] = clientID;
                                        backgroundWorkerTimeline.RunWorkerAsync(tempArguments);
                                    }
}

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then when user hits button I run

            //check for background workers to complete
            if (myInternalLoginClass.backgroundWorkerTimeline.IsBusy) myInternalLoginClass.backgroundWorkerTimeline.CancelAsync();
            while (myInternalLoginClass.backgroundWorkerTimeline.IsBusy)
            {
            }
***next line of code here

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I was thinking that as long as I put in that continuous loop, while busy... do nothing,
the backgroundthread would run until finished, then since it was complete, it would hit ***next line of code here.

but when I try this the loop never exits... the workers stays in IsBusy.

Am I thinking about this the wrong way?  Even when I hit cancelasync and check in the background thread... it stays ISBUSY?

any ideas?