? 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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