在代码优先C＃中出现多对多关系

Question

I am using entity framework code first for creating database in my project. I have defined many to many relationship between following two table.:

1. Student
2. Course

Fluent Api

modelBuilder.Entity<Student>().HasMany(e => e.Courses)
            .WithMany(e => e.Students).Map(m =>
             {
                m.MapLeftKey("StudentId");
                m.MapRightKey("CourseId");
                m.ToTable("StudentCourse");
             });

This will define a many to many relationship between Student and Course and will create a new table StudentCourse in the database.

Now i want to define a new relationship (that may be 1 to 1 OR 1 to many ) between

1. StudentCource
2. Any other table

How can i do this with entity framework code first ??

Answer 1

What do you want is no possible without creating a own class (poco) for the StudentCourse

public class StudentCourse
{
    public int Id {get;set;}
    public Student Student {get; set;}
    public Course Course {get; set;}

}

And then use fluent api to make the relationship between this three variables

modelBuilder.Entity<StudentCourse>()
    .HasRequired(i => i.Student)
    .WithMany(u => u.StudentCourses)
    .HasForeignKey(i => i.StudentId)
    .WillCascadeOnDelete(false);

modelBuilder.Entity<StudentCourse>()
    .HasRequired(i =>i.Course)
    .WithMany(d =>d.StudentCourses)
    .HasForeignKey(i => i.CourseId)
    .WillCascadeOnDelete(false);

Where StudentCourses are the navigation properties in the student class and Course class

You can use the Id defined as primary key or use the foreign key of both tables as primary:

modelBuilder.Entity<StudentCourse>()
    .HasKey(i => new {i.StudentId,i.CourseId });

In my opinion use the Id as primary key make you more simple the things for making relationships between StudentCourse and another table.