How to group with a written specified DataContextClass?

I want to group dvdlist by categoryid, Similar to this, but no DVDDataContext This one works,

DvdDataContext db = new DvdDataContext();
var q = from b in db.DvdLists
        group b by b.CategoryId into g
        select new { CategoryID = g.Key, DvdLists = g };

I need the following kind of code, but the error occurs at GetTable()=g

DataContext db = new DataContext(conString);
var dvd = db.GetTable<DvdList>();
var query = from b in dvd
            group b by b.CategoryId into g
            select new { CategoryId = g.Key, GetTable<DvdList>()= g }; 

You cannot specify GetTable() in anonymous types. Try { CategoryId = g.Key, GetTable= g };

Hope it helps!