C# Linq Join 多表查询

注：闲来无事 来篇博客

1. 三张表

class Teacher　
{
     public int ID { set; get; }
　   public int SchoolNum { set; get; }
     public string TeacherName { set; get; }
     public string TeacherAge { set; get; }
}
class School
{
    public int SchoolNum{ set; get; }
    public string SchoolName { set; get; }
}
class Student
{
    public int ID{ set; get; }
    public int SchoolNum{ set; get; }
    public string StudentName { set; get; }
    public string StudentAge { set; get; }
}

2.输出 School 表中对应人员 Teacher 和 Student 的信息，包括 城市姓名、人员姓名、人员年龄

3.代码

var schoolModel = db.school.ToList();

var teacherModel = db.teacher.ToList();
var result1 = schoolModel.Join(teacherModel, p => p.CityNum, c => c.CityNum, (p, c) => new { CityName = p.CityName, PeopleName = c.TeacherName, PeopleAge = c.TeacherAge }).ToList();

var studentModel = db.student.ToList();
var result2 = schoolModel.Join(studentModel, p => p.CityNum, c => c.CityNum, (p, c) => new { CityName = p.CityName, PeopleName = c.StudentName, PeopleAge = c.StudentAge }).ToList();

result1.AddRange(result2); 
 

4.输出

{ CityName = A学校, PeopleName = "学生A", PeopleAge = "学生A" }

{ CityName = A学校, PeopleName = "教师A", PeopleAge = "教师A" }

{ CityName = B学校, PeopleName = "学生B", PeopleAge = "学生B" }

{ CityName = C学校, PeopleName = "学生C", PeopleAge = "学生C" }