Left Outer Join and Group By In LINQ

List Table1 = new List();
List Table2 = new List();

var objList = from ListData in
                  (from a in Table1
                   join b in Table2 on a.Id equals b.Id into t2
                   from t2Data in t2.DefaultIfEmpty()
                   select new
                   {
                       Product = a.Product,
                       Title = t2Data.Title,
                       Amount = a.Amount
                   }
                )
              group ListData by new
              {
                  ListData.Product,
                  ListData.Title
              } into GroupData
              select new
              {
                  Product = GroupData.Key.Product,
                  Title = GroupData.Key.Title,
                  Amount = GroupData.Sum(OL => OL.Amount)
              };