c# list 数据分组问题

List 使用 var query = from t in F_RCMH_Entity_3iyEnsTable.AsEnumerable()
                        group t by new { t1 = t.Field<string>("FSTARTTIME"), t2 = t.Field<string>("seq") } into m
                        select new
                        {
                            areaid = m.Key.t1,
                            seq = m.Key.t2,
                            house = m.First().Field<string>("FSTARTTIME"),
                            rowcount = m.Count()
                        };