linq group by Having 语句的写法.

//分组，根据2个条件学期和课程，统计各科均分,统计结果放在匿名对象中。两种写法。

02.Console.WriteLine("---------第一种写法");

03.var TermAvgScore_1 = (from l in lst

04.group l by new { Term = l.Term, Course = l.Course } into grouped

05.orderby grouped.Average(m => m.Score) ascending

06.orderby grouped.Key.Term descending

07.select new { Term = grouped.Key.Term, Course = grouped.Key.Course, Scores = grouped.Average(m => m.Score) }).ToList();

08.foreach (var l in TermAvgScore_1)

09.{

10.Console.WriteLine("学期:{0},课程{1},均分{2}", l.Term, l.Course, l.Scores);

11.}

12.Console.WriteLine("---------第二种写法");

13.var TermAvgScore_2 = lst.GroupBy(m => new { Term = m.Term, Course = m.Course })

14..Select(k => new { Term = k.Key.Term, Course = k.Key.Course, Scores = k.Average(m => m.Score) })

15..OrderBy(l => l.Scores).OrderByDescending(l => l.Term);

16.foreach (var l in TermAvgScore_2)

17.{

18.Console.WriteLine("学期:{0},课程{1},均分{2}", l.Term, l.Course, l.Scores);

19.}

Linq中没有SQL中的Having语句，因此是采用where语句对Group后的结果过滤。

原文  : http://www.it165.net/pro/html/201301/4521.html