Хорошо, я нашел решение. Этот код работает:
using (Context context = new Context())
{
var cv =
(
from c in context.CVs
where c.Id == id && c.PersonneId == userId
select new CVVM
{
Titre = c.Titre,
MontrerPhoto = c.MontrerPhoto,
Layout = c.Layout,
Id = id,
FormAction = "EditionTraitement",
FormTitre = "Edition de ce CV",
Formations = from form in c.Formations
where c.Id == id && c.PersonneId == userId
select new FormationVM
{
Id = form.Id,
DateDebut = form.DateDebut,
DateFin = form.DateFin,
Ecole = form.Ecole,
Description = form.Description,
Diplome = form.Diplome
}
}).FirstOrDefault();
}