.NET基础学习(LINQ)

1 string Sex = "男";
2 var person = new { Age = 24, SimpleClass.Name, Sex };
3 Console.WriteLine("{0},Sex{1}，Age {2}",person.Name,person.Sex,person.Age);

 1 var query1 = from n in Enumerable.Range(1, 10)
 2 where n < 8
 3 select n;
 4 Console.Write("查询语法得到结果：");
 5 foreach (var v in query1) Console.Write("{0}\t",v);
 6
 7 var query2 = Enumerable.Range(1, 8).Where(n => n < 8);
 8 Console.WriteLine("");
 9 Console.Write("方法语法得到结果：");
10 foreach (var v in query2) Console.Write("{0}\t", v);
11
12 int count = (from n in Enumerable.Range(1, 10)
13 where n < 8
14 select n).Count();
15 Console.WriteLine("");
16 Console.WriteLine("两种方式的组合：{0}", count);

1 int[] arr = { 1, 5, 9, 8, 45, 23, 26, 14, 7, 8, 9 };
2 var query = from n in arr //(n->迭代变量)
3 where n < 10 //使用迭代变量
4 select n; //使用迭代变量
5 foreach (var v in query) Console.Write("{0}\t",v);
6 Console.WriteLine("");

 1 public class Student
 2  {
 3 public int StID;
 4 public string LastName;
 5  }
 6 public class CourseStudent
 7  {
 8 public string CourseName;
 9 public int StID;
10  }
11
12 CourseStudent[] studentInCourses = new CourseStudent[]{
13 new CourseStudent{CourseName="Art",StID=1},
14 new CourseStudent{CourseName="Art",StID=3},
15 new CourseStudent{CourseName="History",StID=1},
16 new CourseStudent{CourseName="History",StID=2},
17 new CourseStudent{CourseName="Physics",StID=3}
18  };
19 Student[] students = new Student[] {
20 new Student{StID=1,LastName="张三"},
21 new Student{StID=2,LastName="李四"},
22 new Student{StID=3,LastName="王五"}
23  };
24
25 //获取选修2门课以上同学的名字
26 var query = (from s in students
27 join c in studentInCourses on s.StID equals c.StID
28 where (from x in studentInCourses where x.StID==c.StID select x.StID).Count()>1
29 select s.LastName).Distinct();
30 foreach (var v in query) Console.Write("{0}\t",v);
31 Console.WriteLine("");
32 //获取选修历史同学的名字
33 var query1 = from s in students
34 join c in studentInCourses on s.StID equals c.StID
35 where c.CourseName == "History"
36 select s.LastName;
37 foreach (var v in query1) Console.Write("{0}\t", v);

1 var someInts = from a in Enumerable.Range(1, 5) //必须的第一个from子句
2 from b in Enumerable.Range(6, 5) //查询主体的第一个子句
3 where a < 3 && b < 10
4 select new { a, b, sum = a + b }; //匿名类型对象
5 foreach (var v in someInts) Console.WriteLine(v);

1 var someInts = from a in Enumerable.Range(1, 5)
2 from b in Enumerable.Range(6, 5)
3 let sum = a + b //在新的变量中保存结果
4 where sum == 12
5 select new { a, b, sum };
6 foreach (var v in someInts) Console.WriteLine(v);

1 var someInts = from a in Enumerable.Range(1, 5)
2 from b in Enumerable.Range(6, 5)
3 let sum = a + b
4 where sum > 12 //条件一
5 where a==4 //条件二
6 select new { a, b, sum };
7 foreach (var v in someInts) Console.WriteLine(v);

 1 var persons = new[] { //匿名类型的对象数组
 2 new {Name="张三",Sex="男",Age=32,Address="广东深圳"},
 3 new {Name="李四",Sex="男",Age=26,Address="广东广州"},
 4 new {Name="王五",Sex="女",Age=22,Address="广东深圳"},
 5 new {Name="赵六",Sex="男",Age=33,Address="广东东莞"}
 6  };
 7 var query = from p in persons
 8 orderby p.Age
 9 select p;
10 foreach (var p in query) Console.WriteLine("Name:{0},Sex:{1},Age:{2},Address:{3}", p.Name, p.Sex, p.Age, p.Address);

 1 var persons = new[] { //匿名类型的对象数组
 2 new {Name="张三",Sex="男",Age=32,Address="广东深圳"},
 3 new {Name="李四",Sex="男",Age=26,Address="广东广州"},
 4 new {Name="王五",Sex="女",Age=22,Address="广东深圳"},
 5 new {Name="赵六",Sex="男",Age=33,Address="广东东莞"}
 6  };
 7 var query = from p in persons
 8  group p by p.Address;
 9 foreach (var v in query) //枚举分组
10  {
11 Console.WriteLine("{0}",v.Key); //分组键
12 foreach (var t in v) //枚举分组中的项
13  {
14 Console.WriteLine("Name:{0},Sex:{1},Age:{2},Address:{3}", t.Name, t.Sex, t.Age, t.Address);
15  }
16 }

1 var somInts = from a in Enumerable.Range(1, 10)
2 join b in Enumerable.Range(5, 10) on a equals b
3 into groupTemp //查询延续
4 from c in groupTemp
5 select c;
6 foreach (var v in somInts) Console.WriteLine(v);

1 IList<int> list = Enumerable.Range(1, 100).ToList();
2 Func<int, bool> myDel = delegate(int x) { return x % 2 == 1; };//委托匿名方法
3 var countOdd1 = list.Count(myDel);//调用委托
4 var countOdd2 = list.Count(x => x % 2 == 1);//Lambda表达式
5 Console.WriteLine("委托参数得到奇数的个数:{0}",countOdd1);
6 Console.WriteLine("Lambda得到奇数的个数:{0}", countOdd2);