linqgroupbyHaving语句的写法.
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groupby分组
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19.//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。
Console.WriteLine("---------第⼀种写法");
var TermAvgScore_1 = (from l in lst
group l by new { Term = l.Term, Course = l.Course } into grouped
orderby grouped.Average(m => m.Score) ascending
orderby grouped.Key.Term descending
select new { Term = grouped.Key.Term, Course = grouped.Key.Course, Scores = grouped.Average(m => m.Score) }).ToList();
foreach (var l in TermAvgScore_1)
{
Console.WriteLine("学期:{0}，课程{1}，均分{2}", l.Term, l.Course, l.Scores);
}
Console.WriteLine("---------第⼆种写法");
var TermAvgScore_2 = lst.GroupBy(m => new { Term = m.Term, Course = m.Course })
.Select(k => new { Term = k.Key.Term, Course = k.Key.Course, Scores = k.Average(m => m.Score) })
.OrderBy(l => l.Scores).OrderByDescending(l => l.Term);
foreach (var l in TermAvgScore_2)
{
Console.WriteLine("学期:{0}，课程{1}，均分{2}", l.Term, l.Course, l.Scores);
}
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  : www.it165/pro/html/201301/4521.html

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