Linq group by: нужны только неповторяющиеся данные о Partners - C#

IQueryable<UserModel> users = from u in dataContext.aspnet_Users
                        join p in dataContext.Partners on u.UserId equals p.Id
                        join s in dataContext.Sites on p.Id equals s.PartnerId
                        where
                            u.UserName.StartsWith(filter) || p.Name.StartsWith(filter) ||
                            p.SurName.StartsWith(filter) || s.Name.Contains(filter) || s.Url.Contains(filter)
                        select new UserModel
                        {
                            UserId = u.UserId,
                            Email = u.UserName,
                            Name = p.Name
                         }