1. 自定义 Master，Kongfu 类
1 class Master
2 {
3
4 public int Id { get; set; }
5 public string Name { get; set; }
6 public int Age { get; set; }
7 public string MenPai { get; set; }
8 public string Kongfu { get; set; }
9 public int Level { get; set; }
10
11 public override string ToString()
12 {
13 return string.Format("Id:{0},Name:{1},Age:{2},MenPai:{3},Kongfu:{4},Level:{5}", Id, Name, Age,MenPai,Kongfu,Level);
14 }
15 }
1 class Kongfu
2 {
3 public int Id { get; set; }
4 public string Name { get; set; }
5 public int Power { get; set; }
6
7 public override string ToString()
8 {
9 return string.Format("Id:{0},Name:{1},Power:{2}", Id, Name, Power);
10 }
11 }
2. 测试代码
1 class Program
2 {
3 static void Main(string[] args)
4 {
5 var master = new List<Master>()
6 {
7 new Master() { Id = 100, Age = 100, Kongfu = "九阳神功",Level=10,MenPai="华山",Name="李二狗" },
8 new Master() { Id = 50, Age = 10, Kongfu = "九阳神功1" ,Level=5,MenPai="华山",Name="李大狗"},
9 new Master() { Id = 200, Age = 60, Kongfu = "九阳神功2",Level=6,MenPai="华山",Name="李狗蛋" },
10 };
11
12 var kongfu = new List<Kongfu>()
13 {
14 new Kongfu(){Id=1,Name="打狗棒法",Power=90},
15 new Kongfu(){Id=2,Name="打狗棒法1",Power=30},
16 new Kongfu(){Id=3,Name="打狗棒法2",Power=20},
17 };
18
19 //使用LINQ做查询（表达式写法）
20 var res1 = from m in master //from后面设置查询的集合
21 where m.Level > 8 //where跟上条件
22
23 select m;//表示m的结果
24 //select m.Name; //只输出名字
25
26
27 //多个条件
28 var res3 = from m in master
29
30 where m.Level > 8 && m.MenPai == "丐帮"
31
32 select m;
33
34 var res4 = master.Where(m => m.Level > 8 && m.MenPai == "丐帮");
35
36 //LINQ联合查询
37 var res5 = from m in master
38 from k in kongfu
39 where m.Kongfu==k.Name
40 select new { master = m, kongfu = k };
41 //select m;
42 foreach (var temp in res)
43 {
44 Console.WriteLine(temp);
45 }
46
47 //join on 联合查询
48 var res12 = from m in master
49 join k in kongfu on m.Kongfu equals k.Name
50 where k.Power>90
51 select new { master = m, kongfu = k };
52
53
54 //对查询结果升序排序
55 var res7 = from m in master
56
57 where m.Level > 8 && m.MenPai == "丐帮"
58 orderby m.Age
59
60 select m;
61
62 //对查询结果倒序排序
63 var res8 = from m in master
64
65 where m.Level > 8 && m.MenPai == "丐帮"
66 orderby m.Age descending
67
68 select m;
69
70 //对查询结果升序排序
71 var res9 = from m in master
72
73 where m.Level > 8 && m.MenPai == "丐帮"
74 orderby m.Age,m.Level //按照多个字段进行排序，如果字段的属性相同，就按照第二个属性排序
75
76 select m;
77
78 var res10 = master.Where(m => m.Level > 8 && m.MenPai == "丐帮").OrderBy(m => m.Age);
79 var res11 = master.Where(m => m.Level > 8 && m.MenPai == "丐帮").OrderBy(m => m.Age).ThenBy(m=>m.Level);
80
81
82
83 //把人物按照所学功夫进行分类，看下哪个功夫修炼人数最多(分组查询)
84 var res13 = from k in kongfu
85 join m in master on k.Name equals m.Kongfu
86 into groups
87 orderby groups.Count()
88 select new { kongfu = k,count=groups.Count()};
89
90 //按照字段分组
91 var res14 = from m in master
92 group m by m.MenPai
93 into g
94 select new { count=g.Count(),key=g.Key}; //g.Key按照哪个属性分组
95
96 //量词操作符any all判断集合中是否满足某个条件
97 bool res15=master.Any(m => m.MenPai == "丐帮");
98 Console.WriteLine(res15);//只要有一个满足返回true
99
100 bool res16=master.All(m => m.MenPai == "丐帮");//所有都满足才返回true
101
102
103
104 Console.ReadKey();
105 }
106
107 //过滤方法
108 static bool Test1(Master m)
109 {
110 if (m.Level > 8) return true;
111 return false;
112 }
113 }
