分组求和回写所有项

var test = new List<MesStock> { new MesStock {Cuid="1", Deid="1",Pno="1",Sno="1",TotalNums=1},
                new MesStock {Cuid="2", Deid="1",Pno="1",Sno="1",TotalNums=1},
                new MesStock {Cuid="3",Deid="2",Pno="2",Sno="2",TotalNums=2},
                new MesStock {Cuid="4",Deid="2",Pno="2",Sno="2",TotalNums=2},
                new MesStock {Cuid="5",Deid="3",Pno="3",Sno="3",TotalNums=3},
            };
            List<MesStock> res = new List<MesStock>();
            test.GroupBy(x => x.Deid + x.Pno + x.Sno, (x, y) =>
             {
                 var total = y.Sum(a => a.TotalNums);
                 return y.Select(t =>
                 {
                     t.TotalNums = total;
                     res.Add(t);
                     return t;
                 }).ToList();
             }).ToList();
            foreach (var item in res)
            {
                Console.WriteLine(item.Cuid + " | " + item.TotalNums);
            }

朋友问的，，，