Question

Could anybody explain the following code return total ?? decimal.Zero please?

public decimal GetTotal()
{
    // Part Price * Count of parts sum all totals to get basket total
    decimal? total = (from basketItems in db.Baskets
                      where basketItems.BasketId == ShoppingBasketId
                      select (int?)basketItems.Qty * basketItems.Part.Price).Sum();
    return total ?? decimal.Zero;
}

Does it mean the following?

    if (total !=null) return total;
    else return 0;

Answer 1

Yes, that’s what it means. It’s called the null-coalescing operator.

It’s just a syntax shortcut. However, it can be more efficient because the value being read is only evaluated once. (Note that there can also be a functional difference in cases where evaluating the value twice has side effects.)