c# Linq Lamda表达式使用 GroupBy 分组

最新推荐文章于 2025-11-10 18:48:54 发布

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本文通过一个具体的C#编程示例介绍了如何使用LINQ进行数据分组及聚合操作，包括lamda表达式与类SQL语言两种写法。

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
List<Person> persons1 = new List<Person>();

persons1.Add(new Person("张三", "男", 20, 1500, DateTime.Now.AddYears(1)));
persons1.Add(new Person("王成", "男", 32, 3200, DateTime.Now.AddYears(2)));
persons1.Add(new Person("李丽", "女", 19, 1700, DateTime.Now.AddYears(3)));
persons1.Add(new Person("何英", "女", 35, 3600, DateTime.Now.AddYears(4)));
persons1.Add(new Person("何英", "女", 18, 1600, DateTime.Now.AddYears(5)));

//写法1：lamda 表达式写法（推荐）
var ls = persons1.GroupBy(a => a.Name).Select(g => (new Test { name = g.Key, count = g.Count(),
ageC = g.Sum(item => item.Age), moneyC = g.Sum(item => item.Money), birth=g.Max(item=>item.Birthday) }));
//写法2：类SQL语言写法最终编译器会把它转化为lamda表达式
var ls2 = from ps in persons1
group ps by ps.Name
into g
select new Test
{
name = g.Key,
count = g.Count(),
ageC = g.Sum(item => item.Age),
moneyC = g.Sum(item => item.Money),
birth=g.Max(item=>item.Birthday)
};

List<Test> l1= ls.ToList();
List<Test> l2 = ls2.ToList();

Console.ReadKey();

}
}

public class Test
{
public string name { get; set; }
public int count { get; set; }
public int ageC { get; set; }
public int moneyC { get; set; }
public DateTime birth { get; set; }
}

public class Person
{
public string Name { get; set; }
public int Age { get; set; }
public string Sex { get; set; }
public int Money { get; set; }
public DateTime Birthday { get; set; }

public Person(string name, string sex, int age, int money, DateTime birthday)
{
Name = name;
Age = age;
Sex = sex;
Money = money;
Birthday = birthday;
}
}

}