c# Linq及Lamda表达式应用经验之 GroupBy 分组

public partial class Form1 : Form  

    {  

        public Form1()  

        {  

            InitializeComponent();  

        }  

      

        List<Person> persons1 = new List<Person>();  

      

        private void Form1_Load(object sender, EventArgs e)  

        {  

            initForm();  

        }  

        private void initForm()  

        {//窗体初始化  

      

            persons1.Add(new Person("张三", "男", 20, 1500));  

            persons1.Add(new Person("王成", "男", 32, 3200));  

            persons1.Add(new Person("李丽", "女", 19, 1700));  

            persons1.Add(new Person("何英", "女", 35, 3600));  

            persons1.Add(new Person("何英", "女", 18, 1600));  

            dataGridView1.DataSource = persons1;  

      

        }  

      

        private void button1_Click(object sender, EventArgs e)  

        {  

            //******* 对集合按Name属于进行分组GroupBy查询 ********  

            //结果中包括的字段：  

            //1、分组的关键字：Name = g.Key  

            //2、每个分组的数量：count = g.Count()  

            //3、每个分组的年龄总和：ageC = g.Sum(item => item.Age)  

            //4、每个分组的收入总和：moneyC = g.Sum(item => item.Money)  

      

            //写法1：lamda 表达式写法（推荐）  

            var ls = persons1.GroupBy(a => a.Name).Select(g => (new { name = g.Key, count = g.Count(), ageC = g.Sum(item => item.Age), moneyC = g.Sum(item => item.Money) }));  

            //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 { name = g.Key, count = g.Count(), ageC = g.Sum(item => item.Age), moneyC = g.Sum(item => item.Money) };  

      

            dataGridView1.DataSource = ls.ToList();  

           //dataGridView1.DataSource = ls2.ToList();  

        }  

    }  

      

    /// <summary>  

    /// 手动设计一个Person类。用于放到List泛型中  

    /// </summary>  

    public class Person  

    {  

        public string Name { get; set; }  

        public int Age  { get;private set; }  

        public string Sex { get; set; }  

        public int Money { get; set; }  

      

        public Person(string name, string sex, int age, int money)  

        {  

            Name = name;  

            Age = age;  

            Sex = sex;  

            Money = money;  

        }  

    }