Proper handling of a possible System.NullReferenceException in lambda expressions

Question

Here is a question of interest

return _projectDetail.ExpenditureDetails
    .Where(detail => detail.ProgramFund == _programFund
         && detail.Expenditure.User == _creditCardHolder)
    .Sum(detail => detail.ExpenditureAmounts.FirstOrDefault(
        amount => amount.isCurrent && !amount.requiresAudit)
    .CommittedMonthlyRecord.ProjectedEac);

ProjectDetails table structure (1 to many) ExpanditureDetails
CostsDetails (1 to many)
ExpanditureAmounts consumables (1 to 1) CommittedMonthlyRecords

ProjectedEac is the decimal field in CommittedMonthlyRecords.

The problem I discovered in Unit test (albeit an unlikely event) is that the following line may be null:

detail.ExpenditureAmounts.FirstOrDefault(
    amount => amount.isCurrent && !amount.requiresAudit)

My initial request was a nested loop in which I would make several trips to the database, which I do not want to repeat. I looked at what looks like some similar questions, but the solution does not seem to fit .

Any ideas?

Answer 1

?

return _projectDetail.ExpenditureDetails.Where(detail => 
        detail.ProgramFund == _programFund && 
        detail.Expenditure.User == _creditCardHolder
    ).Sum(detail => {
        var a = detail.ExpenditureAmounts.FirstOrDefault(
            amount => amount.isCurrent && !amount.requiresAudit
        );
        return a != null ? a.CommittedMonthlyRecord.ProjectedEac : 0.0m;
    });