Comparing nullable and non-nullable properties on a join (Linq)

Asked Jun 29 '15 at 18:21

Active Jun 29 '15 at 18:21

Viewed 54 times

I am trying to join to tables on a column/property where it is nullable in one table and non-nullable in the other one

var x = from tr in testResults
        join u in Users
        on new { tr.SiteId, tr.UserId.Value } equals new { u.SiteId, u.UserId }                     
        into results
        from r in results.DefaultIfEmpty()
        select tr);

UserId is nullable in testResults and non-nullable in Users. I run into "The type of one of the expressions in the join clause is incorrect. Type inference failed in the call to 'GroupJoin'". Anyone has a suggestion on how to fix this?

asked Jun 29 '15 at 18:21

Sophonias

Perhaps use a default value for the nullable one eg `tr.UserId ?? 0` which will use 0 if tr.UserId is null. – 7thFox Jun 29 '15 at 18:29
1

Did you try `tr.UserId` and `(int?)u.UserId`? I'm not sure if linq-to-sql will like that or not. – juharr Jun 29 '15 at 18:31
@juharr I tried that it linq won't let you put a cast in a join clause. – Sophonias Jun 29 '15 at 18:36
i know nullable types are slower. but if its not a problem why dont you make UserId of Users nullable too? – M.kazem Akhgary Jun 29 '15 at 18:39
Is it possible that `tr.UserId.Value` is a different type than `u.UserId`? Maybe `.Value` converts it to a `string`. – TestWell Jun 29 '15 at 18:40
tr.UserId.GetValueOrDefault(0) seems to fix the problem. – Sophonias Jun 29 '15 at 19:28
Using lambdas with linq I find a lot easier and more powerful. – George Harnwell Jun 29 '15 at 19:33

Comparing nullable and non-nullable properties on a join (Linq)

0 Answers0