Anonymously Hosted DynamicMethods Assembly c# linq

Question

I have a query:

_selectQuery = _selectQuery.Substring(0, _selectQuery.Length - 1) + ")";
    var testData= (from student in view.StudentView
     join  school in db.Schools on student.schoolid equals school.id into schools
    from sc in schools.DefaultIfEmpty()

    join  tr in db.Teacher on sc.id equals tr.schoolid into teacherSchools
    from tsc in teacherSchools.DefaultIfEmpty()
select new
{
school, sc, tsc
}.Select(_selectQuery);


 foreach (var item in testData)
{
   allData.Add(item.ToDynamic());
 }

the code above throws exception in the foreach/iteration part: testData is null.

Anonymously Hosted DynamicMethods Assembly at lambda_method(Closure , <>f__AnonymousType33713 ) at System.Linq.Enumerable.WhereSelectEnumerableIterator2.MoveNext()
at Swift.PeopleCommon.Data.Export.EnhancedExportService.GetGridData(GridJsonGetRows grid, Boolean limitData) at DynamicModule.ns.Wrapped_IEnhancedExportStore_a2d199ba35504f35a326f3807ad0f404.__1(IMethodInvocation inputs, GetNextInterceptionBehaviorDelegate getNext)

I tried addung null checker like

 join  school in db.Schools on student==null ? 0 : student.schoolid equals school.id into something

but still throws error.

I tried creating a class for the select part(eg. select new TestClass{}) instead of anonymous but still throws exception. what could I be missing?

Hamix · Accepted Answer · 2015-10-15 16:13:22Z

1

Check if the tsc in your from tsc in teacherSchools.DefaultIfEmpty() is NULL or not.

Edit 1:

I think the exception is thrown in

select new { school, sc, tsc }

check inner object

select new 
{ 
   School= (school==null ? new School() : school),
   etc
}

edited Oct 15, 2015 at 16:13

answered Oct 15, 2015 at 15:11

Hamix

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4 Comments

Ron Beyer Over a year ago

This should be a comment, not an answer.

Hamix Over a year ago

use generic helper extension method "IfNotNull". see this link stackoverflow.com/a/854619/1476708

user742102 Over a year ago

did I use it correctly like this? join tr in db.Teacher on sc.ifNotNull(g=> g.id) equals tr.ifNotNull(g=> g.schoolid ) into teacherSchools it still throws the same error though.

user742102 Over a year ago

I also used it in the select statement (eg. school = s.isnotNull(s=> s)) still throws the same error. sorry not really sure what's going on coz I can see during debug that one of my left join is null, but isn't the null checker supposed to handle that?

Dhanik Lal Sahni · Accepted Answer · 2016-12-19 06:55:03Z

1

I also got same error. Reason was, one of the db field was set default but db column has value NULL. So i have update that field with default field and that worked fine.

answered Dec 19, 2016 at 6:55

Dhanik Lal Sahni

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