举例来说,我正在使用本文在codeproject上的代码:http : //www.codeproject.com/Articles/234606/Creating-a-Many-To-Many-Mapping-Using-Code-First
我试图在我的代码中做类似的事情,但我也想要一个数量属性,所以:
我在想我必须在PersonCourses表中添加一个名为Quantity的列,但是我不知道如何在Code First中做到这一点。
代码:
public class Person
{
public int PersonId { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public ICollection<Course> CoursesAttending { get; set; }
public Person()
{
CoursesAttending = new HashSet<Course>();
}
}
public class Course
{
public int CourseId { get; set; }
public string Title { get; set; }
public ICollection<Person> Students { get; set; }
public Course()
{
Students = new HashSet<Person>();
}
}
public class SchoolContext : DbContext
{
public DbSet<Course> Courses { get; set; }
public DbSet<Person> People { get; set; }
public SchoolContext()
: base("MyDb")
{
}
}
内容:
public class SchoolContext : DbContext
{
public DbSet<Course> Courses { get; set; }
public DbSet<Person> People { get; set; }
public SchoolContext()
: base("MyDb")
{
}
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Course>().
HasMany(c => c.Students).
WithMany(p => p.CoursesAttending).
Map(
m =>
{
m.MapLeftKey("CourseId");
m.MapRightKey("PersonId");
m.ToTable("PersonCourses");
});
}
}
要将一列添加到联结表中,您需要将其显式映射为实体并创建两个一对多关系:
public class PersonCourse
{
[Key, Column(Order = 0),ForeignKey("Person")]
public int PersonId { get; set; }
[Key, Column(Order = 1),ForeignKey("Course")]
public int CourseId { get; set; }
public Person Person { get; set; }
public Course Course { get; set; }
public int Quantity{ get; set; }
}
public class Person
{
public int PersonId { get; set; }
//...
public ICollection<PersonCourse> CoursesAttending { get; set; }
public Person()
{
CoursesAttending = new HashSet<PersonCourse>();
}
}
public class Course
{
public int CourseId { get; set; }
//...
public ICollection<PersonCourse> Students { get; set; }
public Course()
{
Students = new HashSet<PersonCourse>();
}
}
如果要使用Fluent Api代替数据注释,则可以使用以下配置:
modelBuilder.Entity<PersonCourse>().HasKey(pc => new { pc.PersonId, pc.CourseId});
modelBuilder.Entity<PersonCourse>().HasRequired(pc=>pc.Person).WithMany(p=>p.CoursesAttending).HasForeignKey(pc=>pc.PersonId);
modelBuilder.Entity<PersonCourse>().HasRequired(pc=>pc.Course).WithMany(c=>c.Students).HasForeignKey(pc=>pc.CourseId);
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