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

 1 using System;
 2 using System.Collections.Generic;
 3 using System.Linq;
 4 namespace Redistest02
 5 {
 6     class Program
 7     {
 8         static void Main(string[] args)
 9         {
10             //Console.WriteLine("Hello DoSubscriberAsync!");
11             //MyRedisHelper.DoSubscriberAsync("myredis").Wait(30);
12             //Console.ReadLine();
13
14             //==================准备模拟两张表的数据
15             var list01 = new List<Student>();//3条数据
16             Enumerable.Range(1, 3).ToList().ForEach(c =>
17             {
18                 list01.Add(new Student { id = 11 + c, Name = "qq" + c });
19             });
20
21             var list02 = new List<Student>();//两条数据
22             list02.Add(new Student { id = 12, Name = "qq1" });
23             list02.Add(new Student { id = 13, Name = "qq2" });
24
25             Console.WriteLine("==========左连接==以左边为准=============");
26             //左连接
27             var newlistL = (from q in list01
28                             join a in list02
29                                on q.id equals a.id into qa
30                             from c in qa.DefaultIfEmpty()
31                             select new Student
32                             {
33                                 id = c == null ? 0 : c.id,
34                                 Name = c == null ? "空的" : c.Name
35                             }).ToList();
36             newlistL.ForEach(c => Console.WriteLine($"id={c.id},name={c.Name}"));
37
38             //右连接
39             Console.WriteLine("==========右连接===以右边为准============");
40             var newlistR = (from a in list02
41                             join q in list01
42                                 on a.id equals q.id into qa
43                             from c in qa.DefaultIfEmpty()
44                             select new Student
45                             {
46                                 id = c == null ? 0 : c.id,
47                                 Name = c == null ? "空的" : c.Name
48                             }).ToList();
49             newlistR.ForEach(c => Console.WriteLine($"id={c.id},name={c.Name}"));
50
51             //内连接
52             Console.WriteLine("==========内连接======两边共同的数据=========");
53             var newlistI = (from a in list02
54                             join q in list01
55                                 on a.id equals q.id
56                             select new Student
57                             {
58                                 id = q == null ? 0 : q.id,
59                                 Name = q == null ? "空的" : q.Name
60
61                             }).ToList();
62             newlistI.ForEach(c => Console.WriteLine($"id={c.id},name={c.Name}"));
63
64
65             Enumerable.Range(1, 10).ToList().ForEach(c =>
66             {
67                 Console.WriteLine(c);
68             });
69             var listdata = Enumerable.Empty<Student>();
70             Console.WriteLine($"listdata的集合对象数据是：{listdata.Count()}个,null就会报错的！");
71         }
72     }
73
74     public class Student
75     {
76         public int id { get; set; }
77         public string Name { get; set; }
78         // public DateTime Birthday { get; set; }
79
80         //public IEnumerable<Student> GetSpectionMenthod
81         //{
82         //    get
83         //    {
84         //        //  yield return Enumerable.Empty<Student>().FirstOrDefault();
85         //        yield return new Student { };
86         //    }
87     }
88
89 }

怎么样，看了之后还是很简单的对吧，嘻嘻！