基本数据结构

表设计如下：

入学记录

public class AdmissionRecord

{

    [Key]

    public long Id { get; set; }

    public DateTime AdmissionTime { get; set; }

    public string Remark { get; set; }

}

班级

public class Class

{

    [Key]

    public long Id { get; set; }

    public DateTime CreationTime { get; set; }

    public string ClassName { get; set; }

    public virtual List<Student> Students { get; set; }

}

学生-教师关系表

public class StudentTeacherRelationship

{

    [Key]

    public long Id { get; set; }

    public long StudentId { get; set; }

    public virtual Student Student { get; set; }

    public long TeacherId { get; set; }

    public virtual Teacher Teacher { get; set; }

}

教师

public class Teacher

{

    [Key]

    public long Id { get; set; }

    public string Name { get; set; }

    public string TeacherId { get; set; }

    public virtual List<StudentTeacherRelationship> StudentTeacherRelationships { get; set; }

}

学生

public class Student

{

    [Key]

    public long Id { get; set; }

    public string StudentId { get; set; }

    public string Name { get; set; }

    public long AdmissionRecordId { get; set; }

    //Student-AdmissionRecord 1:1

    [ForeignKey("AdmissionRecordId")]

    public virtual AdmissionRecord AdmissionRecord { get; set; }

    public long ClassId { get; set; }

    public virtual Class Class { get; set; }

    public virtual List<StudentTeacherRelationship> StudentTeacherRelationships { get; set; }

}

一对一

学生-入学记录

public long AdmissionRecordId { get; set; }

//Student-AdmissionRecord 1:1

[ForeignKey("AdmissionRecordId")]

public virtual AdmissionRecord AdmissionRecord { get; set; }

另解

modelBuilder.Entity<Student>()

    .HasOne(p => p.AdmissionRecord)

    .WithOne(p => p.Student)

    .HasForeignKey<Student>(p => p.AdmissionRecordId);

参考资料：

Configuring One To One Relationships In Entity Framework Core

一对多

学生-班级

modelBuilder.Entity<Class>()

    .HasMany(p => p.Students)

    .WithOne(p => p.Class)

    .HasForeignKey(p => p.ClassId)

    .OnDelete(DeleteBehavior.ClientSetNull);

//下面写法也可以

//modelBuilder.Entity<Student>()

//    .HasOne(p => p.Class)

//    .WithMany(p=>p.Students)

//    .HasForeignKey(k => k.ClassId)

//    .OnDelete(DeleteBehavior.ClientSetNull);

多对多

学生-教师

//通过StudentTeacherRelationship中间表，通过实现两个1:n，实现m:n

modelBuilder.Entity<StudentTeacherRelationship>()

    .HasOne(p => p.Student)

    .WithMany(p => p.StudentTeacherRelationships)

    .HasForeignKey(k => k.StudentId)

    .OnDelete(DeleteBehavior.ClientSetNull);

modelBuilder.Entity<StudentTeacherRelationship>()

    .HasOne(p => p.Teacher)

    .WithMany(p => p.StudentTeacherRelationships)

    .HasForeignKey(k => k.TeacherId)

    .OnDelete(DeleteBehavior.ClientSetNull);

示例代码

示例代码