// Show Monsters
 private async void ShowModalPageMonsterList()
 {
     // When you want to show the modal page, just call this method
     // add the event handler for to listen for the modal popping event:
     Crawl.App.Current.ModalPopping += HandleModalPopping;
     _myModalBattleMonsterListPage   = new BattleMonsterListPage();
     await Navigation.PushModalAsync(_myModalBattleMonsterListPage);
 }
 // Helper to handle Modal navigation.
 private void HandleModalPopping(object sender, ModalPoppingEventArgs e)
 {
     if (e.Modal == _myModalBattleMonsterListPage)
     {
         _myModalBattleMonsterListPage = null;
         App.Current.ModalPopping     -= HandleModalPopping;
     }
 }