using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

namespace Lamda

{

    class Program

    {

        static void Main(string[] args)

        {

            #region 测试数据

            List<Student> list = new List<Student>()

        {

        new Student(){ ID=, Name="jack", Age=},

        new Student(){ ID=, Name="mary", Age=},

        new Student(){ ID=, Name="joe", Age=},

         new Student(){ ID=, Name="joe", Age=},

        new Student(){ ID=, Name="Aaron", Age=},

          new Student(){ ID=, Name="Aaron", Age=},

        };

            var a = list.Where((x, i) => list.FindIndex(z => z.ID == x.ID) == i);

            #endregion

            //1、获取list实体某一字段最大值

            var maxvalue = list.Max(p => p.ID);//4

            //2、获取list实体某一字段最小值

            var minvalue = list.Min(p => p.ID);//1

            //3、获取list实体某一字段总和的平均值

            var sumvalue = list.Sum(p => p.ID);//10

            //4、获取list实体某一字段总和的平均值

            var village = list.Average(p => p.ID);//2.5

            //5、判断list实体字段是否包含值

            var Iscon = list.Where(p => p.Name == "jack" && p.Age == ).Any();//false  //是否存在名字为jack,年龄在2岁的人

            //6、list实体转成DICTIONARY 键值对

            var dic = list.Distinct().ToDictionary(p => p.ID, p => p.Name);

            //7、按照某一字段进行分组并获取对应字段的值

            var group = list.GroupBy(p => p.Name).Select(p =>p.Key).ToList();
            //7.1根据某一个字段的值去重
            var group2 =list.GroupBy(p => p.Name).Select(p =>p.First()).ToList();

           //8、根据某一字段获取list实体中重复的数据
           var duplicatevalue = list.GroupBy(p => p.Name).Where(g => g.Count() > ).Select(p => p.Key).ToList();
           //已知Name字段值中有重复值,根据Name字段查出重复值 
           var sbarry = string.Join("','", duplicatevalue.ToArray()); 
           var sdk = list.Where(p => sbarry.Contains(p.Name)).ToList();//找出符合条件的值重复的数据 
         //9、根据某一字段获取list实体中重复的数据 
        var data2 = list.Where(p => list.Count(x => x.Name == p.Name) > ).ToList();//找出符合条件的值重复的数据(这种方法比上8的好处是直接就可以查出实体) 
        int number =  - ; 
        var data = list.Where(p => list.Count(x => x.Name == p.Name) >= number).ToList();//统计重复数据是5条以上的 
       //10、只获取list实体部分字段的值 
       var PartList = list.Select(p => new { p.Name, p.ID}).ToList(); 
       var PartList2 = list.Where(p => p.ID==).Select(p => new { p.Name, p.ID }).ToList(); 
       var r = PartList2.Select(p => p.ID).FirstOrDefault(); foreach (var item in PartList2) { } 
       //11、只获取list实体部分字段的值 
        var PartList3 = list.Select(p => new Student2 { Name = p.Name, ID = p.ID }).ToList(); 
} 
} 

public class Student2 { public int ID { get; set; } public string Name { get; set; } } public class Student { public int ID { get; set; } public string Name { get; set; } public int Age { get; set; } } }

//根据某一字段值获取最大值

            List<testLambdaMax> lmax = new List<testLambdaMax>{

            new testLambdaMax(){Id=,Name="A"},

            new testLambdaMax(){Id=,Name="B"},

            new testLambdaMax(){Id=,Name="C"},

            new testLambdaMax(){Id=,Name="D"}

        };

            var b = lmax.OrderByDescending(t => t.Id).Select(p => p.Name).FirstOrDefault();

//根据list实体中某一字段值去重
            List<Test> t = new List<Test>() {
                new Test(){id=1,name="车辆"},
                new Test(){id=2,name="车辆"},
                new Test(){id=3,name="飞机"},
                new Test(){id=4,name="火车"},
                new Test(){id=4,name="火车"},
            };
            var q = t.Where(d1 => t.Count(d2 => d2.name == d1.name) > 1).Distinct().ToList();