CODEWITHSUNDEEP
c#asp.netlinqasp.net-mvc-4asp.net-mvc-3
Enrique Gil
Enrique Gil

Reputation: 754

Join in LINQ with DefaultIfEmpty still causing NullReferenceException

Is it really possible to cause a NullReferenceException on a join statement even if it has the DefaultIfEmpty() code?

     var getWorkerList = (from a in workerList
                         join ps in db.ProjectStatus on a.StatusId equals ps.StatusId into hjps
                         from ps in hjps.DefaultIfEmpty()
                         join psc in db.StatusColor on ps.StatusCode equals psc.StatusCode into hjpsc
                         from psc in hjpsc.DefaultIfEmpty()
                         join lu in db.LOOKUPS on psc.StatusColorID equals lu.LOOKUPS_ID into hjlu
                         from lu in hjlu.DefaultIfEmpty()
                         select new WorkerModel()
                         {
                            FullName = a.FullName
                            ,Color = lu.LOOKUPS_Code                  
                         }).OrderBy(a => a.WorkerId).ToList();

Here is where I get the NullReferenceException Error :

join lu in db.LOOKUPS on psc.StatusColorID equals lu.LOOKUPS_ID into hjlu
                         from lu in hjlu.DefaultIfEmpty()

When adding this join statement I get the error. Please help.

Upvotes: 1

Views: 1471

Answers (2)

Amir Sherafatian
Amir Sherafatian

Reputation: 2083

you are using 'left join' instead of 'join' by '.DefaultIfEmpty()'

so you have to correct select statement: replace 'Color = lu.LOOKUPS_Code' with this: 'Color = lu == null ? "" : lu.LOOKUPS_Code'.

also you are able to use a different overload of '.DefaultIfEmpty()' to set a replacement instead of 'null', so then the select statement wouldn't throw an exception

Upvotes: 1

nvoigt
nvoigt

Reputation: 77304

.DefaultIfEmpty() returns a sequence with a single default value if the original source is empty.

It will still throw a null reference exception, if the original source is null.

Upvotes: 4

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