private void ListView_ItemSelected(object sender, SelectedItemChangedEventArgs e)
        {
            var item = e.SelectedItem as Contato;
            var page = new EditPage(item);

            Navigation.PushAsync(page);
        }
        private void Button_Clicked(object sender, EventArgs e)
        {
            var page = new EditPage(new Contato());

            Navigation.PushAsync(page);
        }