async void onAddBtnClicked(object sender, EventArgs e)
{
var nextPage = new ElementoCreateUpdatePage(rubricaUid, categoriaUid, true)
{
BindingContext = new Elemento()
};
await Navigation.PushAsync(nextPage);
}
async public void OnEdit(object sender, EventArgs e)
{
var menuItem = ((MenuItem)sender);
Elemento elemento = menuItem.CommandParameter as Elemento;
var nextPage = new ElementoCreateUpdatePage(rubricaUid, categoriaUid, false);
nextPage.BindingContext = elemento;
await Navigation.PushAsync(nextPage);
}