private void AddItemButton_OnClicked(object sender, EventArgs e)
        {
            try
            {
                if (CategoryPicker.SelectedIndex >= 0 && QuantityPicker.SelectedIndex >= 0 &&
                    itemNameBox.Text.Length > 0 && itemPriceBox.Text.Length > 0)
                {
                    var categoryText = CategoryPicker.Items[CategoryPicker.SelectedIndex];
                    var quantityText = QuantityPicker.Items[QuantityPicker.SelectedIndex];

                    Global.CurrentCategory = categoryText;

                    Global.AddItem(
                        new Item(itemNameBox.Text, Convert.ToDouble(itemPriceBox.Text), Convert.ToInt32(quantityText),
                                 categoryText, "999999999"), _editing ? Global.ItemList.IndexOf(_refItem) : -1);

                    if (_editing)
                    {
                        Global.DeleteItem(_refItem);
                    }

                    Navigation.PopModalAsync();
                }
                else if (itemPriceBox.Text.Length == 0)
                {
                    DisplayAlert("Error creating item", "This item has no price", "OK");
                }
                else if (CategoryPicker.SelectedIndex < 0)
                {
                    DisplayAlert("Error creating item", "This item is missing the category", "OK");
                }
                else if (QuantityPicker.SelectedIndex < 0)
                {
                    DisplayAlert("Error creating item", "This order is missing the quantity", "OK");
                }
                else if (itemNameBox.Text.Length == 0)
                {
                    DisplayAlert("Error creating item", "This order is missing the name", "OK");
                }
            }
            catch
            {
                DisplayAlert("Error creating item", "Missing a required field", "OK");
            }
        }