向entity Framework中的多对多实体添加项

// 定义实体类
public class Student
{
    public int StudentId { get; set; }
    public string Name { get; set; }
    public ICollection<Course> Courses { get; set; }
}

public class Course
{
    public int CourseId { get; set; }
    public string Title { get; set; }
    public ICollection<Student> Students { get; set; }
}

// 创建上下文类
public class SchoolContext : DbContext
{
    public DbSet<Student> Students { get; set; }
    public DbSet<Course> Courses { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        // 定义多对多关系
        modelBuilder.Entity<Student>()
            .HasMany<Course>(s => s.Courses)
            .WithMany(c => c.Students)
            .Map(cs =>
            {
                cs.MapLeftKey("StudentId");
                cs.MapRightKey("CourseId");
                cs.ToTable("StudentCourse");
            });
    }
}

// 添加项
using (var context = new SchoolContext())
{
    // 创建一个新的学生对象
    var newStudent = new Student { Name = "John Doe" };

    // 将新的学生对象添加到上下文中
    context.Students.Add(newStudent);

    // 保存更改
    context.SaveChanges();
}