private async void Button_OnClicked(object sender, EventArgs e)
 {
     if (listView.SelectedItem != null)
     {
         if (await App.DisplayMessage(ConstValues.TITLE_STATUS_INFO, ConstValues.MSG_EVENT_PAGE, ConstValues.OPTION_NO, ConstValues.OPTION_YES))
         {
             App.DbAthlete = listView.SelectedItem as DbAthlete;
             _             = RestUtils.AddGameUser(App.DbGame.Id, App.DbAthlete.Id);
             Application.Current.MainPage = new NavigationPage(new RegisterEventPage());
             await Navigation.PushAsync(new RegisterEventPage());
         }
     }
     else
     {
         await App.DisplayMessage(ConstValues.TITLE_STATUS_INFO, ConstValues.MSG_SELECT_ATHLETE, ConstValues.OPTION_OK);
     }
 }