Linq to Sql 聚合查询

//输出体重最大的同学，并要求最大体重得大于39，并按照体重大下，对分组结果进行排序。
                    var result = from query in linq.Student
                                 group query by query.ClassID into gS
                                 where gS.Max<Student>(s => s.StudentWeigth) > 39
                                 orderby gS.Max<Student>(s => s.StudentWeigth) descending
                                 select new
                                 {
                                     ClassID = gS.Key,
                                     MaxWeight = gS.Max<Student>(s => s.StudentWeigth)
                                 };

                    var result = from query in linq.Student
                                group query by query.ClassID into gS

                                 let mw = gS.Max<Student>(s => s.StudentWeigth)

                                where mw > 39
                                select new
                                {
                                    ClassID = gS.Key,
                                    MaxWeight = mw
                                };
                    foreach (var item in result)
                    {
                        Response.Write(string.Format("classid = {0} studentmaxweight = {1}", item.ClassID, item.MaxWeight));
                    }

//查询身高大于132并且体重大于30的Student，并按照StudentID升序排序，按照classID降序排序
var query = from s in db.Students
            where s.HeightInCm > 132 && s.WeightInKg > 30
            orderby s.StudentID ascending, s.ClassID descending
            select s;

//对Student表按照ClassID和Hometown两个字段进行分组，并输出每个班级中某个地方的学生数
var query = from s in db.Students
                        group s by new { s.ClassID, s.Hometown } into gS
                        let cn = gS.Count<Student>()
                        select new
                        {
                            ClassID = gS.Key.ClassID,
                            Hometown = gS.Key.Hometown,
                            Count = cn
                        };
            foreach (var item in query)
            {
                Console.WriteLine("class id = {0} hometown {1} student count = {2}", item.ClassID, item.Hometown,item.Count);
            }

//在上面的基础上加一点点需求，要求分组后的结果按照count排序
var query = from s in db.Students
            group s by new { s.ClassID, s.Hometown } into gS
            let cn = gS.Count<Student>()
            orderby cn descending
            select new
            {
                ClassID = gS.Key.ClassID,
                Hometown = gS.Key.Hometown,
                Count = cn
            };