? Demo模型類:
public class StudentScore { public int ID { set ; get ; } public string Name { set ; get ; } public string Course { set ; get ; } public int Score { set ; get ; } public string Term { set ; get ; } }
Demo示例代碼:
static void Main() { var lst = new List<StudentScore> { new StudentScore {ID = 1 , Name = " 張三 " , Term = " 第一學期 " , Course = " Math " , Score = 80 }, new StudentScore {ID = 1 , Name = " 張三 " , Term = " 第一學期 " , Course = " Chinese " , Score = 90 }, new StudentScore {ID = 1 , Name = " 張三 " , Term = " 第一學期 " , Course = " English " , Score = 70 }, new StudentScore {ID = 2 , Name = " 李四 " , Term = " 第一學期 " , Course = " Math " , Score = 60 }, new StudentScore {ID = 2 , Name = " 李四 " , Term = " 第一學期 " , Course = " Chinese " , Score = 70 }, new StudentScore {ID = 2 , Name = " 李四 " , Term = " 第一學期 " , Course = " English " , Score = 30 }, new StudentScore {ID = 3 , Name = " 王五 " , Term = " 第一學期 " , Course = " Math " , Score = 100 }, new StudentScore {ID = 3 , Name = " 王五 " , Term = " 第一學期 " , Course = " Chinese " , Score = 80 }, new StudentScore {ID = 3 , Name = " 王五 " , Term = " 第一學期 " , Course = " English " , Score = 80 }, new StudentScore {ID = 4 , Name = " 趙六 " , Term = " 第一學期 " , Course = " Math " , Score = 90 }, new StudentScore {ID = 4 , Name = " 趙六 " , Term = " 第一學期 " , Course = " Chinese " , Score = 80 }, new StudentScore {ID = 4 , Name = " 趙六 " , Term = " 第一學期 " , Course = " English " , Score = 70 }, new StudentScore {ID = 1 , Name = " 張三 " , Term = " 第二學期 " , Course = " Math " , Score = 100 }, new StudentScore {ID = 1 , Name = " 張三 " , Term = " 第二學期 " , Course = " Chinese " , Score = 80 }, new StudentScore {ID = 1 , Name = " 張三 " , Term = " 第二學期 " , Course = " English " , Score = 70 }, new StudentScore {ID = 2 , Name = " 李四 " , Term = " 第二學期 " , Course = " Math " , Score = 90 }, new StudentScore {ID = 2 , Name = " 李四 " , Term = " 第二學期 " , Course = " Chinese " , Score = 50 }, new StudentScore {ID = 2 , Name = " 李四 " , Term = " 第二學期 " , Course = " English " , Score = 80 }, new StudentScore {ID = 3 , Name = " 王五 " , Term = " 第二學期 " , Course = " Math " , Score = 90 }, new StudentScore {ID = 3 , Name = " 王五 " , Term = " 第二學期 " , Course = " Chinese " , Score = 70 }, new StudentScore {ID = 3 , Name = " 王五 " , Term = " 第二學期 " , Course = " English " , Score = 80 }, new StudentScore {ID = 4 , Name = " 趙六 " , Term = " 第二學期 " , Course = " Math " , Score = 70 }, new StudentScore {ID = 4 , Name = " 趙六 " , Term = " 第二學期 " , Course = " Chinese " , Score = 60 }, new StudentScore {ID = 4 , Name = " 趙六 " , Term = " 第二學期 " , Course = " English " , Score = 70 }, };
?
// 分組,根據姓名,統計Sum的分數,統計結果放在匿名對象中。兩種寫法。 // 第一種寫法 Console.WriteLine( " ---------第一種寫法 " ); var studentSumScore_1 = ( from l in lst group l by l.Name into grouped orderby grouped.Sum(m => m.Score) select new {Name = grouped.Key, Scores = grouped.Sum(m => m.Score)}).ToList(); foreach ( var l in studentSumScore_1) { Console.WriteLine( " {0}:總分{1} " , l.Name, l.Scores); } // 第二種寫法 Console.WriteLine( " ---------第二種寫法 " ); var studentSumScore_2 = lst.GroupBy(m => m.Name) .Select(k => new {Name = k.Key, Scores = k.Sum(l => l.Score)}) .OrderBy(m => m.Scores).ToList(); foreach ( var l in studentSumScore_2) { Console.WriteLine( " {0}:總分{1} " , l.Name, l.Scores); } // 分組,根據2個條件學期和課程,統計各科均分,統計結果放在匿名對象中。兩種寫法。 Console.WriteLine( " ---------第一種寫法 " ); var TermAvgScore_1 = ( from l in lst group l by new {l.Term, l.Course} into grouped orderby grouped.Average(m => m.Score) ascending orderby grouped.Key.Term descending select new {grouped.Key.Term, grouped.Key.Course, Scores = grouped.Average(m => m.Score)}) .ToList(); foreach ( var l in TermAvgScore_1) { Console.WriteLine( " 學期:{0},課程:{1},均分:{2} " , l.Term, l.Course, l.Scores); } Console.WriteLine( " ---------第二種寫法 " ); var TermAvgScore_2 = lst.GroupBy(m => new {m.Term, m.Course}) .Select(k => new {k.Key.Term, k.Key.Course, Scores = k.Average(m => m.Score)}) .OrderBy(l => l.Scores).ThenByDescending(l => l.Term); foreach ( var l in TermAvgScore_2) { Console.WriteLine( " 學期:{0},課程:{1},均分:{2} " , l.Term, l.Course, l.Scores); } // 分組,帶有Having的查詢,查詢均分>80的學生 Console.WriteLine( " ---------第一種寫法 " ); var AvgScoreGreater80_1 = ( from l in lst group l by new {l.Name, l.Term} into grouped where grouped.Average(m => m.Score) >= 80 orderby grouped.Average(m => m.Score) descending select new { grouped.Key.Name, grouped.Key.Term, Scores = grouped.Average(m => m.Score) }).ToList(); foreach ( var l in AvgScoreGreater80_1) { Console.WriteLine( " 姓名:{0},學期:{1},均分:{2} " , l.Name, l.Term, l.Scores); } Console.WriteLine( " ---------第二種寫法 " ); /* 此寫法看起來較為復雜,第一個Groupby,由于是要對多個字段分組的,因此構建一個匿名對象, 對這個匿名對象分組,分組得到的其實是一個IEnumberable<IGrouping<匿名類型,StudentScore>>這樣一個類型。 Where方法接受,和返回的都同樣是IEnumberable<IGrouping<匿名類型,StudentScore>>類型, 其中Where方法簽名Func委托的類型也就成了Func<IGrouping<匿名類型,StudentScore>,bool>, 之前說到,IGrouping<out TKey, out TElement>繼承了IEnumerable<TElement>, 因此這種類型可以有Average,Sum等方法。 */ var AvgScoreGreater80_2 = lst.GroupBy(l => new {l.Name, l.Term}) .Where(m => m.Average(x => x.Score) >= 80 ) .OrderByDescending(l => l.Average(x => x.Score)) .Select(l => new {l.Key.Name, l.Key.Term, Scores = l.Average(m => m.Score)}).ToList(); foreach ( var l in AvgScoreGreater80_2) { Console.WriteLine( " 姓名:{0},學期:{1},均分:{2} " , l.Name, l.Term, l.Scores); } Console.ReadKey(); }
原文地址:
http://hi.baidu.com/tewuapple/item/5e0e5a2862b67a8b9c63d103
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