private void OnQtyPickerSelectedIndexChanged(object sender, EventArgs e)
{
var qty = int.Parse(_qtyPicker.Items[_qtyPicker.SelectedIndex]);
var item = App.Database.GetItem(_selectedCartItemId);
item.Quantity = qty;
App.Database.SaveItem(item);
_cartViewModel.SetCartItemQty(_selectedCartItemId, qty);
}