如何使用外键在LINQ中插入两个以上的表

Question

I am apparently Inserting data using LINQ by creating classes of tables in the databases but it just has error that says object is null.

This is my sample code using C# LINQ:

using (dc = new linqDBDataContext(conn))
{
    Subject_Curriculum sc;
    Subject_Schedule ss;
    Subject_Department sd;
    Subject_Standing sst;

    Pre_Requisite pr;
    Pre_Requisite_Year_Standing prys;

    Curriculum cu = new Curriculum();
    cu.Curriculum_Title = curriculumName;
    cu.Course_Number = courseNumber;

    foreach (var s in ssd)
    {
        sc = new Subject_Curriculum();
        sc.Course_Code = s.courseCode;
        sc.Course_Title = s.courseTitle;
        cu.Subject_Curriculums.Add(sc);
        dc.Subject_Curriculums.InsertOnSubmit(sc);

        for (int i = 0; i < s.numberOfSchedules; i++)
        {
            ss = new Subject_Schedule();

            if (i == 0)
            {
                ss.Units = s.unitsLec;
                ss.Schedule_Type = "Lecture";
                ss.Number_Of_Hours = s.numberOfHoursLec;
            }
            else
            {
                ss.Units = s.unitsLab;
                ss.Schedule_Type = "Laboratory";
                ss.Number_Of_Hours = s.numberOfHoursLab;
            }

            sc.Subject_Schedules.Add(ss);
            dc.Subject_Schedules.InsertOnSubmit(ss);
        }

        foreach (var sdl in s.department)
        {
            sd = new Subject_Department();
            sd.Department_Number = sdl;
            sc.Subject_Departments.Add(sd);
            dc.Subject_Departments.InsertOnSubmit(sd);
        }

        sst = new Subject_Standing();
        sst.Year = s.year;
        sst.Semester = s.semester;

        cu.Subject_Standings.Add(sst);
        dc.Subject_Standings.InsertOnSubmit(sst);

        if (s.yearStandingStatus)
        {
            prys = new Pre_Requisite_Year_Standing();
            prys.Year_Standing = Convert.ToInt32(s.yearStanding.ToString().Substring(0, 1));
            sc.Pre_Requisite_Year_Standings.Add(prys);
            dc.Pre_Requisite_Year_Standings.InsertOnSubmit(prys);
        }
        else
        {
            if (s.prereq.Count == 0)
            {
                pr = new Pre_Requisite();
                pr.Pre_Requisite_Code = null;
                sc.Pre_Requisites.Add(pr);
                dc.Pre_Requisites.InsertOnSubmit(pr);
            }
            else
            {
                foreach (var p in s.prereq)
                {
                    pr = new Pre_Requisite();
                    pr.Pre_Requisite_Code = Convert.ToInt32(p);
                    sc.Pre_Requisites.Add(pr);
                    dc.Pre_Requisites.InsertOnSubmit(pr);
                }
            }
        }
    }

    dc.Curriculums.InsertOnSubmit(cu);
    dc.SubmitChanges();

    return true;
}

As you can see in the code, the Curriculum table has the highest hierarchy in the database and the other tables inherits its primary key into Subject_Curriculum, Pre_Requisite, Subject_Standing and Pre_Requisite_Year_Standing. While Subject_Schedules and Subject_Department inherits Subject_Curriculum's primary key. What can I do to make this insertion possible to all table at once?

Answer 1

I already solved my question. It is just by adding all tables from their foreign keys and insert and submit changes at the end of the loop. This makes this thread close.