Entity Framework: The argument to DbIsNullExpression must refer to a primitive or reference type

Question

I\'m trying to use entity to do this:

    SELECT *
    FROM aspnet_Users u LEFT JOIN (SELECT u.UserId, p.Permission, p.MediaId, p.Valid
                              


        

Answer 1

Had a similar problem, I managed to solve it by moving the null check outside of the sql. In your case you can do it by calling ToList() before checking for Null:

var intermediateUl = from us in en.aspnet_Users
    join pm in up
      on us.UserId equals pm.UserId into pmOuter
    from pm2 in pmOuter.DefaultIfEmpty()
    select new { us.UserName, us.UserId, pm2};

var ul = intermediateUl
    .ToList()
    .Select(o => new PermissionInfo { 
        Permission = (o.pm2 == null ? -1 : pm2.Permission1), 
        PermissionId = (o.pm2 == null ? -1 : pm2.PermissionId) 
        UserName = o.UserName, 
        UserId = o.UserId, 
     });

The problem surprised me as well, because couple lines above I had a similar query with outer join which passed OK. It seems that checking for null with linq outer construct is only possible with entities known by Entity Framework. Any other class, anonymous or not, confuses EF/linq.

I know this question is old, but maybe it will help someone :)