var query2 = from i in proba.id_person
                     select i.id;
        foreach (var k in query2)
        {
            var upit = from l in proba.name
                       join f in proba1.last_name on l.id equals f.id
                       where l.id == k
                       select new { l.ime, f.prezime };

            foreach (var g in upit) { 

            model.Add(new ViewModel
            {

                Name = g.ime,
                last_name = g.prezime,
                id_person = k

            });
            }
        }          

        return View(model);

Why I have this error: The specified LINQ expression contains references to queries that are associated with different contexts.