用C#的LINQ进行select查询、where过滤、group分组和join关联的操作

最编程 2024-08-10 16:07:39

...

using System;
using System.Collections.Generic;
using System.Linq;

namespace ConsoleApp1
{
class Program
{
static void Main(string[] args)
{
List<Student> students = new List<Student>()
{
new Student() {name="张三", age=22, telephone="1234567890"},
new Student() {name="张四", age=23, telephone="1234567891"},
new Student() {name="王五", age=21, telephone="1234567892"}
};
// 替换
var query1 = from student in students
orderby student.age descending
select student.name.Replace("张四", "李四");
// 自定义方法
var query2 = from student in students
orderby student.age descending
select MyFunc(student.name);
// 匿名类型
var query3 = from student in students
orderby student.age descending
select new { name=student.name + "OK!", age=student.age+10};
// 对查询结果投影
var query4 = from student in students
orderby student.age descending
select new Student{ name = student.name, age = 25, telephone=""};
foreach (var s in query1)
{
Console.WriteLine(s);
}
foreach (var s in query2)
{
Console.WriteLine(s);
}
foreach (var s in query3)
{
Console.WriteLine(s.name + " " + s.age);
}
foreach (var s in query4)
{
Console.WriteLine(s.name + " " + s.age);
}
static string MyFunc(string s)
{
return s + "好！";
}
Console.ReadLine();
}
}

public class Student
{
public string name { get; set; }
public int age { get; set; }
public string telephone { get; set; }
}
}

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