Is it possible to subscribe to a lib event on a REST request and wait for a return?

I would like to know if it is possible to subscribe to a third party lib event, which in this case is Microsoft.Speech.dll, because in my attempt, it didnt work, that is, the recognition does not happen and the event is not triggered. I tried using Task and without, but nothing. I don’t really know if it’s possible to subscribe to an event that way and the request wait it. Follow the code.