protected override bool OnBackButtonPressed()
 {
     Model.DisposeModel();
     MessagingCenter.Unsubscribe <ZonesPlanViewModel>(this, "Rebuild");
     MessagingCenter.Unsubscribe <ZonesPlanViewModel>(this, "Reshape");
     base.OnBackButtonPressed();
     return(false);
 }
 protected override bool OnBackButtonPressed()
 {
     Model.DisposeModel();
     base.OnBackButtonPressed();
     return(false);
 }