Linq query containing null value

Question

var records = from entity in q1.question_papers
              select new
              {
                  QuestionPaperID = entity.QUESTION_PAPER_ID,
                  SubjectID = entity.SUBJECT_ID,       
                  PreviousAttempts = SubIdAtt.Where(c => c.SUBID == entity.SUBJECT_ID)
                                             .Select(c => c.ATT)   
                                             .FirstOrDefault(),
              };

Above is my linq query where in PreviousAttempts field I get null value if doesn't satisfy where. So instead of containing null I want to change this 0 if it contains null and restore original value if it doesn't contain non null value.

How can I achieve this since I am not able to change PreviousAttempts through for each of record?

James · Accepted Answer · 2013-10-28 16:26:04Z

9

You can use the null-coalescing operator here e.g.

PreviousAttempts = SubIdAtt.Where(c => c.SUBID == entity.SUBJECT_ID)
                           .Select(c => c.ATT)
                           .FirstOrDefault() ?? 0;

Or alternatively, if you want to keep it all LINQified use the DefaultIfEmpty method e.g.

PreviousAttempts = SubIdAtt.Where(c => c.SUBID == entity.SUBJECT_ID)
                           .Select(c => c.ATT)
                           .DefaultIfEmpty(0)
                           .FirstOrDefault();

edited Oct 28, 2013 at 16:26

answered Oct 28, 2013 at 16:09

James

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Sam · Accepted Answer · 2013-10-28 16:10:30Z

6

You could use the coalescing operator. ??

           var records = from entity in q1.question_papers
                           select new
                           {
                               QuestionPaperID = entity.QUESTION_PAPER_ID,
                               SubjectID = entity.SUBJECT_ID,

                               PreviousAttempts = SubIdAtt.Where(c => c.SUBID == entity.SUBJECT_ID).Select(c => c.ATT).FirstOrDefault() ?? 0
                           };

answered Oct 28, 2013 at 16:10

Sam

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