public Balance Subtract(Amount amount)
{
if (amount == null || !amount.Quantity.HasValue)
{
throw new BalanceError(BalanceError.ErrorMessageCannotSubtractUninitializedAmountFromBalance);
}
if (amount.IsRealZero)
{
return(this);
}
if (Amounts.ContainsKey(amount.Commodity))
{
Amount existingAmount = Amounts[amount.Commodity];
existingAmount.InPlaceSubtract(amount);
if (existingAmount.IsRealZero)
{
Amounts.Remove(amount.Commodity);
}
}
else
{
Amounts.Add(amount.Commodity, amount.Negated());
}
return(this);
}
public void DeleteFromCart(Food food, int amount)
{
Items.Remove(food);
Amounts.Remove(amount);
}