我有问题,因为当我将以下内容添加到课程Course
时,我只有2张桌子而不是3
public int PersonId { get; set; }
[ForeignKey("PersonId")]
public virtual Person Student { get; set; }
你没有这三条线路都很好,但我需要在课程
中增加一个字段public class Person
{
public int PersonId { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public virtual ICollection<Course> CoursesAttending { get; set; }
}
public class Course
{
public int CourseId { get; set; }
public string Title { get; set; }
public int PersonId { get; set; }
[ForeignKey("PersonId")]
public virtual Person Student { get; set; }
public virtual ICollection<Person> Students { get; set; }
}
public class SchoolContext : DbContext
{
public DbSet<Course> Courses { get; set; }
public DbSet<Person> People { get; set; }
}
class Program
{
static void Main(string[] args)
{
Database.SetInitializer<SchoolContext>(
new DropCreateDatabaseAlways<SchoolContext>());
SchoolContext db = new SchoolContext();
var cos = from d in db.Courses
select d;
}
}
请帮帮我
答案 0 :(得分:5)
EF无法决定Course.Student
或Course.Students
是否引用Person.CoursesAttending
。您必须为EF提供一个提示,例如使用[InverseProperty]
上的Course.Students
属性:
[InverseProperty("CoursesAttending")]
public virtual ICollection<Person> Students { get; set; }
修改强>
该模型将导致多个级联删除路径,即:当您删除连接表中的Person
个记录时也会被删除,但它也会删除此人所有的Course
个通过Course.Person
属性分配。删除的Course
将再次删除连接表中的记录,这是同一个表中的第二个删除路径。
SQL Server不允许多个级联删除路径,因此必须使用Fluent API禁用它:
public class MyContext : DbContext
{
//...
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Course>()
.HasRequired(c => c.Student)
.WithMany()
.HasForeignKey(c => c.PersonId)
.WillCascadeOnDelete(false);
}
}