排序操作符，包括OrderBy、OrderByDescending、ThenBy、ThenByDescending和Reverse，提供了升序或者降序排序。
OrderBy操作符将序列中的元素按照升序排列。
注意：orderby必须在select之前出现,查询表达式最后只可能出现select或者groupby。
student类：
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace 排序操作符
8 {
9 public class Student
10 {
11
12 //姓名
13 public string Name { get; set; }
14 //成绩
15 public int Score { get; set; }
16 public int Order { get; set; }
17 //构造函数
18 public Student(string name, int score, int order)
19 {
20 this.Name = name;
21 this.Score = score;
22 this.Order = order;
23 }
24 }
25 }
teacher类：
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace 排序操作符
8 {
9 /// <summary>
10 /// Teacher类
11 /// </summary>
12 public class Teacher
13 {
14 //姓名
15 public string Name { get; set; }
16 //学生集合
17 public List<Student> Students { get; set; }
18
19 public Teacher(string name, List<Student> students)
20 {
21 this.Name = name;
22 this.Students = students;
23 }
24 }
25 }
Program：
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace 排序操作符
8 {
9 class Program
10 {
11 static void Main(string[] args)
12 {
13 //使用集合初始化器初始化Teacher集合
14 List<Teacher> teachers = new List<Teacher> {
15 new Teacher("徐老师",
16 new List<Student>(){
17 new Student("宋江",80,1),
18 new Student("卢俊义",95,2),
19 new Student("朱武",45,3)
20 }
21 ),
22 new Teacher("姜老师",
23 new List<Student>(){
24 new Student("林冲",90,2),
25 new Student("花荣",85,4),
26 new Student("柴进",58,5)
27 }
28 ),
29 new Teacher("樊老师",
30 new List<Student>(){
31 new Student("关胜",100,6),
32 new Student("阮小七",70,7),
33 new Student("时迁",30,0)
34 }
35 )
36 };
37
38 #region OrderBy
39 //OrderBy 表达式
40 var queryOrderBy = from t in teachers
41 from s in t.Students
42 where s.Score < 60
43 orderby s.Order
44 select s;
45 //方法
46 var query = teachers.SelectMany(p => p.Students).Where(s => s.Score < 60).OrderBy(s => s.Order).Select(s => s);
47 foreach (var item in queryOrderBy)
48 {
49 Console.WriteLine("姓名:"+item.Name+",分数:"+item.Score);
50 }
51 foreach (var item in query)
52 {
53 Console.WriteLine("姓名:" + item.Name + ",分数:" + item.Score);
54 }
55 #endregion
56
57 Console.ReadKey();
58 }
59 }
60 }
运行结果：
二、OrderByDescending
OrderByDescending操作符将序列中的元素按照降序排列。
示例：
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace 排序操作符
8 {
9 class Program
10 {
11 static void Main(string[] args)
12 {
13 //使用集合初始化器初始化Teacher集合
14 List<Teacher> teachers = new List<Teacher> {
15 new Teacher("徐老师",
16 new List<Student>(){
17 new Student("宋江",80,1),
18 new Student("卢俊义",95,2),
19 new Student("朱武",45,3)
20 }
21 ),
22 new Teacher("姜老师",
23 new List<Student>(){
24 new Student("林冲",90,2),
25 new Student("花荣",85,4),
26 new Student("柴进",58,5)
27 }
28 ),
29 new Teacher("樊老师",
30 new List<Student>(){
31 new Student("关胜",100,6),
32 new Student("阮小七",70,7),
33 new Student("时迁",30,0)
34 }
35 )
36 };
37
38 #region OrderByDescending
39 //表达式
40 var queryDesc = from t in teachers
41 from s in t.Students
42 where s.Score < 60
43 orderby s.Order descending
44 select s;
45 //方法
46 var query1 = teachers.SelectMany(p => p.Students).Where(s => s.Score < 60).OrderByDescending(s => s.Order).Select(s => s);
47 foreach (var item in queryDesc)
48 {
49 Console.WriteLine("姓名:" + item.Name + ",分数:" + item.Score);
50 }
51 foreach (var item in queryDesc)
52 {
53 Console.WriteLine("姓名:" + item.Name + ",分数:" + item.Score);
54 }
55 #endregion
56
57 Console.ReadKey();
58 }
59 }
60 }
运行效果：
三、ThenBy排序
ThenBy操作符实现按照次关键字对序列进行升序排列。此操作符的查询语法和方法语法略有不同，例如：
//查询语法
var query=from e in Employees orderby e.FirstName,e.LastName select e;
//方法语法
var q=Employees.OrderBy(e=>e.FirstName).ThenBy(e=>e.LastName).Select(e=>e);
示例：
Category类：
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace ThenBy
8 {
9 public class Category
10 {
11 public Guid CategoryId { get; set; }
12 public string CategoryName { get; set; }
13 public int Order { get; set; }
14 }
15 }
Products类：
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace ThenBy
8 {
9 public class Products
10 {
11 public Guid Id { get; set; }
12 public Guid CategoryId { get; set; }
13 public string Name { get; set; }
14 public int Order { get; set; }
15 public DateTime CreateTime { get; set; }
16 }
17 }
Program:
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace ThenBy
8 {
9 class Program
10 {
11 static void Main(string[] args)
12 {
13 List<Products> pro = new List<Products>() {
14 new Products(){Id=Guid.NewGuid(),Name="格林童话",CategoryId=Guid.NewGuid(),Order=1,CreateTime=DateTime.Now.AddHours(2)},
15 new Products(){Id=Guid.NewGuid(),Name="美女与野兽",CategoryId=Guid.NewGuid(),Order=1,CreateTime=DateTime.Now},
16 new Products(){Id=Guid.NewGuid(),Name="世界如此险恶，您的内心需要强大",CategoryId=Guid.NewGuid(),Order=0,CreateTime=DateTime.Now.AddHours(3)}
17 };
18 //查询语法
19 var query = (from p in pro orderby p.Order, p.CreateTime select p);
20 //方法
21 var q = pro.OrderBy(p => p.Order).ThenBy(p => p.CreateTime).Select(p => p);
22 foreach (var item in query)
23 {
24 Console.WriteLine("name:"+item.Name+"id:"+item.Id+",order:"+item.Order+",CreateTime:"+item.CreateTime);
25 }
26 foreach (var item in q)
27 {
28 Console.WriteLine("name:" + item.Name + "id:" + item.Id + ",order:" + item.Order + ",CreateTime:" + item.CreateTime);
29 }
30
31 Console.ReadKey();
32 }
33 }
34 }
运行效果：
四、ThenByDescending
ThenByDescending操作符实现按照次关键字对序列进行降序排列。此操作符的查询语法与方法语法略有不同，例如：
//查询语法
var query=from e in Employees orderby e.FirstName,e.LastName descending select e;
//方法语法
var q=Employees.OrderBy(e=>e.FirstName).ThenByDescending(e=>e.LastName).Select(e=>e);
示例：
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace ThenBy
8 {
9 class Program
10 {
11 static void Main(string[] args)
12 {
13 List<Products> pro = new List<Products>() {
14 new Products(){Id=Guid.NewGuid(),Name="格林童话",CategoryId=Guid.NewGuid(),Order=1,CreateTime=DateTime.Now.AddHours(2)},
15 new Products(){Id=Guid.NewGuid(),Name="美女与野兽",CategoryId=Guid.NewGuid(),Order=1,CreateTime=DateTime.Now},
16 new Products(){Id=Guid.NewGuid(),Name="世界如此险恶，您的内心需要强大",CategoryId=Guid.NewGuid(),Order=0,CreateTime=DateTime.Now.AddHours(3)}
17 };
18 //查询语法
19 var query = from p in pro orderby p.Order, p.CreateTime descending select p;
20 //方法
21 var q = pro.OrderBy(p => p.Order).ThenByDescending(p => p.CreateTime);
22 foreach (var item in query)
23 {
24 Console.WriteLine("name:" + item.Name + "id:" + item.Id + ",order:" + item.Order + ",CreateTime:" + item.CreateTime);
25 }
26 foreach (var item in q)
27 {
28 Console.WriteLine("name:" + item.Name + "id:" + item.Id + ",order:" + item.Order + ",CreateTime:" + item.CreateTime);
29 }
30
31 Console.ReadKey();
32 }
33 }
34 }
运行效果：
五、Reverse
Reverse将会把序列中的元素按照从后到前的顺序反转。需要注意的是，Reverse方法的返回值是void,例如：
var q=Employees.Select(e=>e.FirstName).ToList();
q.Reverse();
示例：
1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace ThenBy
8 {
9 class Program
10 {
11 static void Main(string[] args)
12 {
13 string[] str = { "A", "B", "C", "D", "E"};
14 var query = str.Select(p => p).ToList();
15 query.Reverse();
16 foreach (var item in query)
17 {
18 Console.WriteLine(item);
19 }
20
21 Console.ReadKey();
22 }
23 }
24 }
运行效果：
时间： 2024-10-28 20:47:44