public void VoidSale()
{
SaleLineItem[] sliToDelete = SaleLineItems.ToArray();
for (int i = 0; i < sliToDelete.Length; i++)
{
SaleLineItems.Remove(sliToDelete[i]);
}
}
public void CancelSaleLineItem(MenuProduct menuProduct)
{
SaleLineItem sli = SaleLineItems.Where(s => s.MenuProduct == menuProduct).FirstOrDefault();
SaleLineItems.Remove(sli);
}