通过Fluent API 配置EF Core多对多关系，首先我们需要在两个类中添加集合导航属性，接着使用UsingEntity方法添加关联表
1 例子：Fluent API多对多关系
如下两个实体类 Student & Teacher
public class Student{public int Id { get; set; }public string Name { get; set; }}public class Teacher{public int Id { get; set; }public string Name { get; set; }}
public class Student{public int Id { get; set; }public string Name { get; set; }public IList<Teacher> Teacher { get; set; } //collection navigation property}public class Teacher{public int Id { get; set; }public string Name { get; set; }public IList<Student> Student { get; set; } //collection navigation property}
public class SchoolContext : DbContext{public DbSet<Teacher> Teacher { get; set; }public DbSet<Student> Student { get; set; }public SchoolContext(DbContextOptions<SchoolContext> options) : base(options){}protected override void OnModelCreating(ModelBuilder modelBuilder){//Write Fluent API configurations heremodelBuilder.Entity<Teacher>().HasMany(t => t.Student).WithMany(t => t.Teacher).UsingEntity(j => j.ToTable("TeacherStudent"));}}
2 EF Core 5.0 以及之前版本
针对EF Core 5.0以及之前的版本，创建多对多关系的过程是不同的，我们首先需要创建一个关联实体，我们将这个关联名称叫做TeacherStudent，你也可以起个别的名字
关联表包含了两个实体的外键，该实体的主键由这两个外键组合而成
public class TeacherStudent{public Student Student { get; set; }public Teacher Teacher { get; set; }}
通过下列配置多对多关系
第一步 – 在关联表中添加外键属性
public class TeacherStudent{public int StudentId { get; set; } //foreign key propertypublic Student Student { get; set; } //Reference navigation propertypublic int TeacherId { get; set; } //foreign key propertypublic Teacher Teacher { get; set; } //Reference navigation property}
第一步 – 在另外实体中添加集合导航属性
public class Student{public int Id { get; set; }public string Name { get; set; }public IList<TeacherStudent> TeacherStudent { get; set; } //collection navigation property}public class Teacher{public int Id { get; set; }public string Name { get; set; }public IList<TeacherStudent> TeacherStudent { get; set; } //collection navigation property}
modelBuilder.Entity<TeacherStudent>().HasKey(t => new { t.StudentId, t.TeacherId });modelBuilder.Entity<TeacherStudent>().HasOne(t => t.Student).WithMany(t => t.TeacherStudent).HasForeignKey(t => t.StudentId);modelBuilder.Entity<TeacherStudent>().HasOne(t => t.Teacher).WithMany(t => t.TeacherStudent).HasForeignKey(t => t.TeacherId);
全部代码
public class SchoolContext : DbContext{public DbSet<Teacher> Teacher { get; set; }public DbSet<Student> Student { get; set; }public DbSet<TeacherStudent> TeacherStudent { get; set; }protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder){if (!optionsBuilder.IsConfigured){optionsBuilder.UseSqlServer(@"Server=vaio;Database=Company;Trusted_Connection=True;");}}protected override void OnModelCreating(ModelBuilder modelBuilder){//Write Fluent API configurations heremodelBuilder.Entity<TeacherStudent>().HasKey(t => new { t.StudentId, t.TeacherId });modelBuilder.Entity<TeacherStudent>().HasOne(t => t.Student).WithMany(t => t.TeacherStudent).HasForeignKey(t => t.StudentId);modelBuilder.Entity<TeacherStudent>().HasOne(t => t.Teacher).WithMany(t => t.TeacherStudent).HasForeignKey(t => t.TeacherId);}}
总结
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