silverlight - Disable DispatcherTimer while a phone call is active on WP7 -

my wp7 (silverlight) app keeps getting rejected because "should not continue vibrating in case of incoming phone call". however, reacting on applicaton_deactivated event not allow me fix problem since method not called on incoming phone call...

the problematic vibration done through dispatchertimer, keeps running in background behind phone call. moving execution main thread didn't change anything.

do apps continue running behind phone calls? or there way stop vibration?

initialization of vibrator , timer:

vibrator = vibratecontroller.default; vibratortimer = new dispatchertimer(); vibratortimer.tick += new eventhandler(vibraterepatedly); vibratortimer.interval = new timespan(0, 0, 0, 0, uiconstants.vibration_interval); vibrationspan = new timespan(0, 0, 0, 0, uiconstants.vibration_duration); 

tick method:

private void vibraterepatedly(object sender, eventargs e) {     vibrator.start(vibrationspan); } 

during incoming call obscured event called , not application_deactivated event. obscured event in app, can't distinguish if due incoming call, incoming sms or reminder.

here link msdn documentation of obscured event get. there corresponding unobscured event can detect.