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group by

编程语言 ganggelove 11℃ 0评论

转自 c# Linq及Lamda表达式应用经验之 GroupBy 分组 – 随风% – 博客园

//自己的
var re = list.GroupBy(p => p.sex).Select(g => new { Mcount = g.Count(),sex=g.Key ,name=g.ToList()});
foreach (var item in re)
{
    if (item.Mcount >= 2)
    {
         //大于等于2行
    }
}
public partial class Form1 : Form  
    {  
        public Form1()  
        {  
            InitializeComponent();  
        }  

        List persons1 = new List();  

        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();  
        }  
    }  

    ///   
    /// 手动设计一个Person类。用于放到List泛型中  
    ///   
    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;  
        }  
    }

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