CancelAsync

I have a form that is constantly using an asynchronous query. It works well (most of the time, but that is a separate issue).

When I close my windows form, I issue a CancelAsync command, this also works.... most of the time. Occasionally I get an error when the form is closed, I can replicate this error by commenting out the CancelAsync line in the FormClosing event. Therefore I can safely conclude that the CancelAsync command occasionally  does not 'take'. The documentation mentions a race condition may sometimes occur, I believe this is the case.

My question therefore is, what is the recommended solution for ensuring an async command is cancel when called from a FormClosing event?

Thanks