Prevent EF from saving full object graph - entity-framework

Question

I have a model as below
public class Lesson
{
public int Id { get; set; }
public Section Div { get; set; }
}
public class Section
{
public int Id { get; set; }
public string Name { get; set; }
}
I also have DB Context as below
public class MyContext : DbContext
{
public MyContext() : base("DefaultConnection")
{
this.Configuration.LazyLoadingEnabled = false;
this.Configuration.ProxyCreationEnabled = false;
}
public DbSet<Lesson> Lessons { get; set; }
public DbSet<Section> Sections { get; set; }
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
base.OnModelCreating(modelBuilder);
}
}
Then I use the following code to call the database
using (MyContext c = new EFTest.MyContext())
{
Lesson d = new EFTest.Lesson();
Section ed = new EFTest.Section() { Name = "a" };
d.Div = ed;
c.Entry(d.Div).State = EntityState.Detached;
c.Lessons.Add(d);
c.SaveChanges();
}
I am expecting this code to save just the Lesson object, not to save the full graph of Lesson and Section, but what happens is that it saves the full graph.
How do I prevent it from doing that?

Answer 1

When you add an entity to DbSet, entityframework will add all of its relative. You need to detach the entity you don't want to add, after adding parent entity to DbSet.
using (MyContext c = new EFTest.MyContext())
{
Lesson d = new EFTest.Lesson();
Section ed = new EFTest.Section() { Name = "a" };
d.Div = ed;
c.Lessons.Add(d);
c.Entry(d.Div).State = EntityState.Detached;
c.SaveChanges();
}
if you want to add section, related to the lesson , you need to use the same context, or create a new context and load the lesson.
you can use this code
using (MyContext c = new EFTest.MyContext())
{
Lesson d = new EFTest.Lesson();
Section ed = new EFTest.Section() { Name = "a" };
d.Div = ed;
c.Lessons.Add(d);
c.Entry(d.Div).State = EntityState.Detached;
c.SaveChanges();
//you can use this code
ed.Lesson = d;
// or this code
d.Div = ed;
c.Sections.Add(ed);
c.SaveChanges();
}