Cancelling an async task without a CancellationToken

I have seen a number of examples of how to write asynchronous tasks which include the CancellationToken to allow them to be cancelled. My problem is finding a simple way to cancel a method such as:

                MapLocationFinderResult result =
                    await MapLocationFinder.FindLocationsAsync(
                                        addressToGeocode,
                                        hintPoint,
                                        resultCount);

This call is made inside an async method which is called from an event handler.

I want to present a busy indicator and a CANCEL button on the screen but I need a way to cancel the "await" when the button is clicked (and of course to know it has been cancelled so I can prevent some other actions from occurring).

If I work my way far enough through the inheritances then I eventually come to a Cancel method in the IAsyncInfo interface but I don't know if or how this can be used.

Any help would be appreciated.

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Woke up one day and realised reality television had destroyed too many brain cells so started writing App's to re-start my brain.