C# LINQ .GroupBy语法

//SUM(已送货数量)
var listSumDOs = _Database.GetQueryable<tb_DO_Cartons>()
    .Where(w => w.DONO != input.DocNo && q_DOs.Any(a => a.SONO == w.SONO && a.PFNO == w.PFNO))
    .GroupBy(g => new { g.SONO, g.PFNO })//SQL:group by SONO,PFNO
    .Select(s => new
    {
        SONO = s.Key.SONO,
        PFNO = s.Key.PFNO,
        Qty = s.Sum(i => i.Qty ?? 0),//SUM(送货数)
    }).ToList();

            //GroupBy语法
            var tmp = from a in listSource
                      where a.FlagPrint == "N"
                      group a by new { a.SONO, a.PFNO } into g
                      select new
                      {
                          SONO = g.Key.SONO,
                          PFNO = g.Key.PFNO,
                          Count = g.Count(),//相同销售单、生产单重复的记录数
                      };
            var result = tmp.Where(w => w.Count > 1).ToList();