LINQ NullReferenceException on DefaultIfEmpty

Question

I'm looking for a solution to the problem of having the DefaultIfEmpty() extension method not picking up null values when used in a LINQ outer join.

Code as follows:

            var SummaryLossesWithNets = (from g in SummaryLosses
                                     join n in nets
                                     on g.Year equals n.Year into grouping
                                     from x in grouping.DefaultIfEmpty()
                                     select new
                                         {
                                             Year = g.Year,
                                             OEPGR = g.OccuranceLoss,
                                             AEPGR = g.AggregateLoss,
                                             OEPNET = ((x.OEPRecovery == null) ? 0 : x.OEPRecovery),
                                             AEPNET = ((x.AEPRecovery == null) ? 0 : x.AEPRecovery),
                                         });

In the List SummaryLosses there are many years worth of data I wish to join to the table 'nets' which contains a sub-portion of the years. The exception is thrown on x being a null value, I am assuming because the years in SummaryLosses not matched by years in nets creates null values in the grouping list.

How should one go about checking for the null value here? As you can see I've attempted to check for null on the properties of x, but since x is null this doesn't work.

Kind regards Richard

Answer 1

Simply check whether x is null instead:

OEPNET = x == null ? 0 : x.OEPRecovery,
AEPNET = x == null ? 0 : x.AEPRecovery

Or if x.OEPRecovery and x.AEPRecovery are nullable properties too, use:

OEPNET = x == null ? 0 : (x.OEPRecovery ?? 0),
AEPNET = x == null ? 0 : (x.AEPRecovery ?? 0)

Answer 2

If you have many join statements

check check all joined tables and ensure that the foreign key you are using (in comparing or lets say Interested in) is not null