private void btnAdd_Click(object sender, System.EventArgs e)
        {
            frmNewItem newItemForm = new frmNewItem();
            InvItem    invItem     = newItemForm.GetNewItem();

            if (invItem != null)
            {
                invItems += invItem;
            }
        }
        private void btnDelete_Click(object sender, System.EventArgs e)
        {
            int i = lstItems.SelectedIndex;

            if (i != -1)
            {
                InvItem invItem = invItems[i];
                string  message = "Are you sure you want to delete "
                                  + invItem.Description + "?";
                DialogResult button =
                    MessageBox.Show(message, "Confirm Delete",
                                    MessageBoxButtons.YesNo);
                if (button == DialogResult.Yes)
                {
                    invItems -= invItem;
                }
            }
        }
 private void HandleChange(InvItemList invItems)
 {
     invItems.Save();
     FillItemListBox();
 }