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 Student10 {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 Teacher13 {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 Program10 {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 OrderBy39 //OrderBy 表达式40 var queryOrderBy = from t in teachers41 from s in t.Students42 where s.Score < 6043 orderby s.Order44 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 #endregion56 57 Console.ReadKey();58 }59 }60 }
运行结果：
二、OrderByDescending
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 Program10 {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 OrderByDescending39 //表达式40 var queryDesc = from t in teachers41 from s in t.Students42 where s.Score < 6043 orderby s.Order descending44 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 #endregion56 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 Category10 {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 Products10 {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 Program10 {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
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 Program10 {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 Program10 {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：
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