public static StoreBill operator -(StoreBill bill1, StoreBill bill2)
{
StoreBill NewBill = new StoreBill();
if (bill1 == null & bill2 == null)
{
NewBill.Articles = null;
}
else if (bill1 == null)
{
NewBill.Articles = bill2.Articles;
}
else if (bill2 == null)
{
NewBill.Articles = bill1.Articles;
}
else
{
NewBill.Articles = bill1.Articles;
foreach (Article artBill2 in bill2.Articles)
{
foreach (Article artNewBill in NewBill.Articles)
{
if (artBill2.Item == artNewBill.Item)
{
artNewBill.Price = Math.Abs(artNewBill.Price - artBill2.Price);
artNewBill.Quantity = Math.Abs(artNewBill.Quantity - artBill2.Quantity);
}
else
{
NewBill.Articles.Add(artBill2);
}
}
}
}
return(NewBill);
}
public void CopyFrom(StoreBill bill)
{
Articles = bill.Articles;
}