core的 Linq基本使用，简单模拟数据库多表的左右内连接的测试

1：先看效果：

 

2：部分代码截图

 

3：全部代码

using System;
using System.Collections.Generic;
using System.Linq;
namespace Redistest02
{
    class Program
    {
        static void Main(string[] args)
        {
            //Console.WriteLine("Hello DoSubscriberAsync!");
            //MyRedisHelper.DoSubscriberAsync("myredis").Wait(30);
            //Console.ReadLine();

            //==================准备模拟两张表的数据
            var list01 = new List<Student>();//3条数据
            Enumerable.Range(1, 3).ToList().ForEach(c =>
            {
                list01.Add(new Student { id = 11 + c, Name = "qq" + c });
            });

            var list02 = new List<Student>();//两条数据
            list02.Add(new Student { id = 12, Name = "qq1" });
            list02.Add(new Student { id = 13, Name = "qq2" });

            Console.WriteLine("==========左连接==以左边为准=============");
            //左连接
            var newlistL = (from q in list01
                            join a in list02
                               on q.id equals a.id into qa
                            from c in qa.DefaultIfEmpty()
                            select new Student
                            {
                                id = c == null ? 0 : c.id,
                                Name = c == null ? "空的" : c.Name
                            }).ToList();
            newlistL.ForEach(c => Console.WriteLine($"id={c.id},name={c.Name}"));

            //右连接
            Console.WriteLine("==========右连接===以右边为准============");
            var newlistR = (from a in list02
                            join q in list01
                                on a.id equals q.id into qa
                            from c in qa.DefaultIfEmpty()
                            select new Student
                            {
                                id = c == null ? 0 : c.id,
                                Name = c == null ? "空的" : c.Name
                            }).ToList();
            newlistR.ForEach(c => Console.WriteLine($"id={c.id},name={c.Name}"));

            //内连接
            Console.WriteLine("==========内连接======两边共同的数据=========");
            var newlistI = (from a in list02
                            join q in list01
                                on a.id equals q.id
                            select new Student
                            {
                                id = q == null ? 0 : q.id,
                                Name = q == null ? "空的" : q.Name

                            }).ToList();
            newlistI.ForEach(c => Console.WriteLine($"id={c.id},name={c.Name}"));


            Enumerable.Range(1, 10).ToList().ForEach(c =>
            {
                Console.WriteLine(c);
            });
            var listdata = Enumerable.Empty<Student>();
            Console.WriteLine($"listdata的集合对象数据是：{listdata.Count()}个,null就会报错的！");
        }
    }

    public class Student
    {
        public int id { get; set; }
        public string Name { get; set; }
        // public DateTime Birthday { get; set; }

        //public IEnumerable<Student> GetSpectionMenthod
        //{
        //    get
        //    {
        //        //  yield return Enumerable.Empty<Student>().FirstOrDefault();
        //        yield return new Student { };
        //    }
    }

}

怎么样，看了之后还是很简单的对吧，嘻嘻！