//中间表
    public class Middle
    {
        [Key]
        public int MiddleID { set; get; }
        [ForeignKey("Student")]
        public int StudentID { set; get; }
        [ForeignKey("Subject")]
        public int SubjectID { set; get; }

        public virtual Student Student { set; get; }
        public virtual Subject Subject { set; get; }
    }
    

    //学生表
    public class Student
    {
        [Key]
        public int StudentID { set; get; }

        [Column("StudentName")]
        public string StudentName { set; get; }

        [Column("BeiZhu")]
        public string BeiZhu { set; get; }

        public virtual ICollection<Middle> Middle { set; get; }
    }


    //科目表
    public class Subject
    {
        [Key]
        public int SubjectID { set; get; }

        [Column("SubjectName")]
        public string SubjectName { set; get; }

        public virtual ICollection<Middle> Middle { set; get; }
    }