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

I realize that since in the second query,it still have the left join with aspnet_Users table, it does not need to have u in the 1st query, so I changed it to below, it works now. But still, it will be great to know why the original code and suggested code failed.

    var up = from u in en.aspnet_Users
                     join p in en.Permissions
                         on u.UserId equals p.UserId into pu
                     from p2 in pu.DefaultIfEmpty()
                     where p2.MediaId == this.MediaId && p2.Valid == true
                     select p2;

            var ul = from us in en.aspnet_Users
                     join pm in up
                          on us.UserId equals pm.UserId into pm1
                     from pm2 in pm1.DefaultIfEmpty()
                     orderby us.LoweredUserName
                     select new PermissionInfo
                     {
                         Permission = (pm2 == null ? -1 : pm2.Permission1),
                         UserName = us.UserName,
                         UserId = us.UserId,
                         PermissionId = (pm2 == null ? -1 : pm2.PermissionId)
                     };

            ret = ul.ToList();