在EFCore中多对多关系的设计数据插入与查询

学生类Student

public class Student
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
    public List<Teacher> Teachers { get; set; }=new List<Teacher>();
}

老师类Teacher

public class Teacher
{
    public int Id { get; set; }
    public string Name { get; set; }
    public List<Student> Students { get; set; }=new List<Student>();
}

实体配置类StudetnConfig

public class StudentConfig : IEntityTypeConfiguration<Student>
{
    public void Configure(EntityTypeBuilder<Student> builder)
    {
        builder.ToTable("Student");
        builder.HasMany<Teacher>(s =>s.Teachers).WithMany(t => t.Students).UsingEntity(s=>s.ToTable("StudentTeacher"));
    }
}

MyDbContext数据上下文类

 public DbSet<Student> Students { get; set; }

 public DbSet<Teacher> Teachers { get; set; }

数据插入

//添加数据

//多对多
using MyDbContext db = new MyDbContext();
Student s1 = new Student { Name = "S1" ,Age=18 };
Student s2 = new Student { Name = "S2", Age = 19 };
Teacher t1 = new Teacher { Name = "T1" };
Teacher t2 = new Teacher { Name = "T2" };

s1.Teachers.Add(t1);
s1.Teachers.Add(t2);
s2.Teachers.Add(t1);
s2.Teachers.Add(t2);


           

db.Teachers.Add(t1);
db.Teachers.Add(t2);

db.Students.Add(s1);
db.Students.Add(s2);
db.SaveChanges();

数据查询

var teachers  = db.Teachers.Include(t=>t.Students).ToList();
  foreach (var t in teachers)
 {
     Console.WriteLine("老师名字:"+t.Name);
     foreach (var s in t.Students)
     {
         Console.WriteLine("\t学生名字:"+s.Name+"---年龄: "+s.Age);
     }
 }
 Console.WriteLine("Hello, World!");
 Console.ReadLine();