How to save multiple model to Db Context (EF)

Question

I am stuck on saving my model on Db Context, I am not sure where to start or how I will proceed.

I have 3 Models (This is a strip version for easier reading)

public class Student
{
    [Required]
    public int Id { get; set; }
    public virtual List<SyTerm> SyTerm { get; set; }
}

public class SyTerm
{
    [Required]
    public int Id { get; set; }
    public virtual List<Course> Courses { get; set; }
}
public class Course
{
    [Required]
    public int Id { get; set; }
}

My problem here is when I try to save it in using Entity Framework

        db.Courses.Add(cortemp1);
        db.Courses.Add(cortemp2);

        db.Students.Add(stud);
        ...
        db.SaveChanges();

I always get an error (Various Error like conflicting, etc.) I am not sure the right sequence on how would I save it.

For example I have this

    var stud = new Student();
    var sys = new List<SyTerm>();
    var cours = new List<Course>();

    var sytemp1 = new SyTerm();
    var sytemp2 = new SyTerm();

    var cortemp1 = new Course();
    var cortemp2 = new Course();

How should I sequence it to save it in my Db?

Anshul Nigam · Accepted Answer · 2015-11-20T05:48:50.423

1

First of all, you dont need multiple save changes if you have you entity relationship in correct way so do something like this

var stud = new Student();
var sys = new List<SyTerm>();
var cours = new List<Course>();



var sytemp1 = new SyTerm();
var sytemp2 = new SyTerm();

sys.Add(sytemp1);//add data to collection
var cortemp1 = new Course();
var cortemp2 = new Course();


  stud.SysTerm = sys;// here we are saying that student entity has this collection

 dbCtx.Student.add(stud); // just add student
 dbCtx.SaveChanges()

In simple terms add all object to student then just add it and save changes as student is now one complete entity. For exact sample look at http://www.entityframeworktutorial.net/code-first/simple-code-first-example.aspx

edited Nov 20 '15 at 05:48

answered Nov 20 '15 at 05:40

Anshul Nigam

1,608
1
12
26

Does it work? I mean in this scenario I assume the program automatically adds the data of SyTerm on database – Franz Justin Buenaventura Nov 20 '15 at 05:45
@FranzJustinBuenaventura, yes it is one complete entity, you dont have to explicit save child entity if you have proper relationship defined – Anshul Nigam Nov 20 '15 at 05:47
1

@FranzJustinBuenaventura I agree with Anshul Nigam that you should assign values to relations - EF cannot figure it out himself, that you want it to be added for that specific object – BeardedMan Nov 20 '15 at 05:48
@FranzJustinBuenaventura, look at http://www.entityframeworktutorial.net/code-first/simple-code-first-example.aspx – Anshul Nigam Nov 20 '15 at 05:49
I never knew EF have this capability. It is smarter than I expected – Franz Justin Buenaventura Nov 20 '15 at 05:59

BeardedMan · Answer 2 · 2015-11-20T05:38:33.653

0

I think you should have relation between Course and SyTerm, so your Course should look like:

public class Course
{
   [Required]
   public int Id { get; set; }
   public virtual SyTerm { get; set; }
}

then of course you have to initialize it if it is required

edited Nov 20 '15 at 05:38

answered Nov 20 '15 at 05:31

BeardedMan

384
2
12

Is it redundant? My original model is like that, with an addition of having SyTerm having a virtual Student. – Franz Justin Buenaventura Nov 20 '15 at 05:42

score 0 · Answer 3 · edited May 23 '17 at 11:59

When adding/updating Entity Framework entities, you have to make sure you consider the DB foreign key relation and map it correctly. In you case SysTerm have list of Courses, but course should also have one SysTerm Id property, to make sure correct one to many relation maintained. Sample shown below how to create entity relationship in correct way

public class Student
{
    public Student()
    { 

    }
    public int StudentID { get; set; }
    public string StudentName { get; set; }

    //Foreign key for Standard
    public int StandardRefId { get; set; }

    [ForeignKey("StandardRefId")]
    public Standard Standard { get; set; }
}

public class Standard
{
    public Standard()
    { 

    }
    public int StandardId { get; set; }
    public string StandardName { get; set; }

    public ICollection<Student> Students { get; set; }

 }

Please check this answer for more details : Understanding ForeignKey attribute in entity framework code first

I think the public virtual are substitute for the manually declaring foreign keys — Franz Justin Buenaventura, Nov 20 '15 at 06:00
Just marking property virtual will not help you. You still need to specify the reference. http://stackoverflow.com/questions/21856218/understanding-foreignkey-attribute-in-entity-framework-code-first — Avinash Jain, Nov 20 '15 at 06:06

How to save multiple model to Db Context (EF)

3 Answers3