一、目的:测试再EntityFrameWorkCore中如何建立一对一、一对多和多对多模型
二、环境:VS2019、.NetCore 2.2、Mysql 8.0、Win10
三、一对一模型的建立:
1、定义模型
示例:学生和桌子的一对一关系:每个学生需要对应一个桌位信息,桌位信息不用包含学生信息
public class Desk
{
public int Id { get; set; }
public string Name { get; set; }
public Student Student { get; set; }
}
public class Student
{
public int Id { get; set; }
public string Name { get; set; }
public int DeskID { get; set; }
public Desk Desk { get; set; }
}
在Student中定义 DeskID和Desk模型,在Desk表中定义Student模型
2、在DataContext中定义两者的关系
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
// Do:一对一关系模型
modelBuilder.Entity<Student>().HasOne(l => l.Desk).WithOne(l => l.Student)
.HasForeignKey<Student>(l => l.DeskID);
}
public DbSet<Student> Students { get; set; }
public DbSet<Desk> Desks { get; set; }
此时通过迁移命令将会生成Students表和Desks表
四、一对多的关系模型定义
1、定义模型
示例:学校和老师的一对多关系:一个学校对应多个老师,一个老师对应一个学校
public class School
{
public int Id { get; set; }
public string Name { get; set; }
public List<Teacher> Teachers { get; set; }
}
public class Teacher
{
public int Id { get; set; }
public string Name { get; set; }
public int SchoolID { get; set; }
public School School { get; set; }
}
2、在DataContext中定义两者的关系
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
// Do:一对多关系模型
modelBuilder.Entity<Teacher>().HasOne(l => l.School).WithMany(l => l.Teachers)
.HasForeignKey(l => l.SchoolID);
}
public DbSet<Teacher> Teachers { get; set; }
public DbSet<School> Schools { get; set; }
此时通过迁移命令将会生成Schools表和Teachers表
五、多对多的关系模型
1、定义模型:
示例:建立父母和孩子的多对多模型,父母可以对应多个孩子,孩子可以有父亲,母亲的对应关系
// Do:定义父母类型
public class Parent
{
public Parent()
{
this.RelationShips =new List<RelationShip>();
}
public int Id { get; set; }
public string Name { get; set; }
// Do:3、定义关系集合
public List<RelationShip> RelationShips { get; set; }
}
// Do:定义子类型
public class Child
{
public Child()
{
this.RelationShips=new List<RelationShip>();
}
public int Id { get; set; }
public string Name { get; set; }
// Do:2、定义关系集合
public List<RelationShip> RelationShips { get; set; }
}
/// <summary>
/// 1、多对多关系模型
/// </summary>
public class RelationShip
{
public int ChildID { get; set; }
public Child Child { get; set; }
public int ParentID { get; set; }
public Parent Parent { get; set; }
}
2、在DataContext中定义两者的关系
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
// Do:多对多配置联合主键
modelBuilder.Entity<RelationShip>().HasKey(l => new {l.ChildID, l.ParentID});
// Do:多对多定义关系模型映射(本段代码可有可无)
modelBuilder.Entity<RelationShip>().HasOne(l => l.Child).WithMany(l => l.RelationShips)
.HasForeignKey(l => l.ChildID);
modelBuilder.Entity<RelationShip>().HasOne(l => l.Parent).WithMany(l => l.RelationShips)
.HasForeignKey(l => l.ParentID);
}
public DbSet<Teacher> Teachers { get; set; }
public DbSet<School> Schools { get; set; }
此时通过迁移命令将会生成Schools表和Teachers表
Github下载地址:https://github.com/HeBianGu/.NetCore-LearnDemo.git