Lambda中的一些方法的总结

　　　　public List<UserInfoBaseModel> GetNameByIDList(List<int> UserID)
        {
            var UserList = LoadRepository<User_Info>()
                           .GetModel()
                           .Where(x => UserID.Contains(x.UserInfoID))
                           .Select(i => new UserInfoBaseModel()
                           {
                               UserInfoId = i.UserInfoID,
                               UserName = i.UserName
                           })
                           .ToList();
            return UserList;
        }

 

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Lambda的各种语法
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Student> list = new List<Student>()
            {
                new Student(){ StudentID = 1, Name = "张飞", Age = 38, Gender = 1},
                new Student(){ StudentID = 2, Name = "关羽", Age = 48, Gender = 1},
                new Student(){ StudentID = 3, Name = "刘备", Age = 37, Gender = 1},
                new Student(){ StudentID = 4, Name = "貂蝉", Age = 20, Gender = 2},
                new Student(){ StudentID = 5, Name = "孙尚香", Age = 19, Gender = 2},
                new Student(){ StudentID = 6, Name = "甄宓", Age = 17, Gender = 2},
                new Student(){ StudentID = 7, Name = "大乔", Age = 18, Gender = 2},
                new Student(){ StudentID = 8, Name = "小乔", Age = 18, Gender = 2},
                new Student(){ StudentID = 9, Name = "马云禄", Age = 20, Gender = 2},
                new Student(){ StudentID = 10, Name = "蔡琰", Age = 21, Gender = 2},
                new Student(){ StudentID = 11, Name = "祝融", Age = 17, Gender = 2},
                new Student(){ StudentID = 12, Name = "关凤", Age = 16, Gender = 2},
                new Student(){ StudentID = 13, Name = "隐藏", Age = 16, Gender = 2},
                new Student(){ StudentID = 14, Name = "英雄", Age = 16, Gender = 2},
            };
            List<StudentExtension> list1 = new List<StudentExtension>()
            {
                new StudentExtension(){ ID = 1, StudentID = 1, Range = "蜀国", TeacherName = "张三"},
                new StudentExtension(){ ID = 2, StudentID = 2, Range = "蜀国", TeacherName = "李四"},
                new StudentExtension(){ ID = 3, StudentID = 3, Range = "蜀国", TeacherName = "王二"},
                new StudentExtension(){ ID = 4, StudentID = 4, Range = "汉", TeacherName = "麻子"},
                new StudentExtension(){ ID = 5, StudentID = 5, Range = "吴国", TeacherName = "王五"},
                new StudentExtension(){ ID = 6, StudentID = 6, Range = "魏国", TeacherName = "赵六"},
                new StudentExtension(){ ID = 7, StudentID = 7, Range = "吴国", TeacherName = "张三"},
                new StudentExtension(){ ID = 8, StudentID = 8, Range = "吴国", TeacherName = "李四"},
                new StudentExtension(){ ID = 9, StudentID = 9, Range = "蜀国", TeacherName = "王二"},
                new StudentExtension(){ ID = 10, StudentID = 10, Range = "汉", TeacherName = "麻子"},
                new StudentExtension(){ ID = 11, StudentID = 11, Range = "蜀国", TeacherName = "王五"},
                new StudentExtension(){ ID = 12, StudentID = 12, Range = "蜀国", TeacherName = "赵六"},
                new StudentExtension(){ ID = 12, StudentID = 12, Range = "蜀国", TeacherName = "赵六11"},
                new StudentExtension(){ ID = 12, StudentID = 12, Range = "蜀国", TeacherName = "赵六22"},
                new StudentExtension(){ ID = 12, StudentID = 12, Range = "蜀国", TeacherName = "赵六33"},
            };

            ///select 返回一个匿名函数
            var lambda1 = list.Select(i => new { i.Age, i.Name, i.StudentID, i.Gender });
            foreach (var item in lambda1)
            {
                Console.WriteLine(item.StudentID + "\t" + item.Name + "\t" + item.Age + "\t" + item.Gender);
            }
            Console.WriteLine("select  -----end");
            ///where
            var lambda2 = list.Where(i => i.Age < 30).Select(i => new { i.Age, i.Name, i.StudentID, i.Gender });
            foreach (var item in lambda2)
            {
                Console.WriteLine(item.StudentID + "\t" + item.Name + "\t" + item.Age + "\t" + item.Gender);
            }
            Console.WriteLine("where  -----end");
            ///OrderBy 升序
            var lambda3 = list.OrderBy(i => i.Age);
            foreach (var item in lambda3)
            {
                Console.WriteLine(item.StudentID + "\t" + item.Name + "\t" + item.Age + "\t" + item.Gender);
            }
            Console.WriteLine("OrderBy  -----end");
            ///OrderByDescending 降序
            var lambda4 = list.OrderByDescending(i => i.Age);
            foreach (var item in lambda4)
            {
                Console.WriteLine(item.StudentID + "\t" + item.Name + "\t" + item.Age + "\t" + item.Gender);
            }
            Console.WriteLine("OrderByDescending  -----end");
            //group子句进行分组
            var lambda5 = list.GroupBy(i => i.Age);
            foreach (var item in lambda5)
            {
                Console.WriteLine(item.Key);
                foreach (var item1 in item)
                {
                    Console.WriteLine(item1.StudentID + "\t" + item1.Name + "\t" + item1.Age + "\t" + item1.Gender);
                }
            }


            ///多表链接
            ///lambda内连接
            var lambda6 = list.Join(list1,
                                    x => x.StudentID,//x对应的是list
                                    c => c.StudentID,//c对应的是list1
                                    (x, c) => new StudentView()//第三个参数对设置返回的数据类型
                                    {
                                        Age = x.Age,
                                        Range = c.Range,
                                        Name = x.Name,
                                        Gender = x.Gender,
                                        StudentID = x.StudentID,
                                        TeacherName = c.TeacherName
                                    }).ToList();


            ///lambda分组链接
            var lambda7 = list.GroupJoin(list1,
                                          x => x.StudentID,//x对应的是list
                                          c => c.StudentID,//c对应的是list1
                                          (x, c) => new //第三个参数对设置返回的数据类型
                                          {
                                              Age = x.Age,
                                              Name = x.Name,
                                              Gender = x.Gender,
                                              StudentID = x.StudentID,
                                              V = c
                                          }).ToList();
            foreach (var item in lambda7)
            {
                Console.WriteLine(item.StudentID + "\t" + item.Name + "\t" + item.Age + "\t" + item.Gender + "我是Key");
                foreach (var item1 in item.V)//item.v中是匹配到的数据集合
                {
                    Console.WriteLine(item1.ID + "\t" + item1.Range + "\t" + item1.StudentID + "\t" + item1.TeacherName);
                }
            }

            Console.ReadLine();
        }
    }

    public class Student
    {
        [DisplayName("学生的ID")]
        public int StudentID { get; set; }
        [DisplayName("学生姓名")]
        public string Name { get; set; }
        [DisplayName("学生的年龄")]
        public int Age { get; set; }
        /// <summary>
        /// 1男2女3未设置
        /// </summary>
        [DisplayName("学生的性别")]
        public int Gender { get; set; }

    }
    public class StudentExtension
    {
        public int ID { get; set; }
        public int StudentID { get; set; }
        public string Range { get; set; }
        public string TeacherName { get; set; }
    }
    public class StudentView
    {
        public int StudentID { get; set; }
        public string Name { get; set; }
        public int Age { get; set; }
        /// <summary>
        /// 1男2女3未设置
        /// </summary>
        public int Gender { get; set; }
        public int ID { get; set; }
        public string Range { get; set; }
        public string TeacherName { get; set; }
    }
}