Save Appointment task dows not fire the Grids focus Event

Save Appointment task dows not fire the Grids focus Event

I am working on saving Appointments But if I do A (new
SaveAppointmentTask()).Show()
Then it doesnot fire the Grids OnFocus event when doing a save or a
Cancel. Please Direct me to a proper step of detecting that the Xaml page
is In Focus ie the current Page.
Here's The XAML and the CS
<Grid OnFocus="Grid_Focus"></Grid>
Cs
private void OnFocus(args args){
//if I put a break point here then it does not hit
}
Please look into it.