async void onAddBtnClicked(object sender, EventArgs e)
        {
            Rubrica newRubrica = new Rubrica();
            var     nextPage   = new RubricaCreateUpdatePage(true);

            nextPage.BindingContext = newRubrica;

            await Navigation.PushAsync(nextPage);
        }
        async public void OnEdit(object sender, EventArgs e)
        {
            var     menuItem = ((MenuItem)sender);
            Rubrica rubrica  = menuItem.CommandParameter as Rubrica;

            var nextPage = new RubricaCreateUpdatePage(false);

            nextPage.BindingContext = rubrica;
            await Navigation.PushAsync(nextPage);
        }