Linq中的group by多表多字段

var q =
    from p in db.Products
    group p by p.CategoryID into g
    select g;

from a in TableA
    join b in TableB on a.Id equals b.aId
    where ((b.Type == 1 || b.Type == 2 || b.Type == 5) && b.State == 1)
    group new { a.Id, b.Name,b,CreateDate } by new { a.Id, b.Name } into g
    select (new Class1 { Id = g.Key.Id, Name = g.Key.Name ?? "" });
 
class Class1
{
    public int Id { get; set; }
    publid string Name { get; set; }