Why Does Entity Framework generate update clause to update foreign key

Question

User-623162908 posted

public class a
{
  [Key]
  public int id{get;set;}
}

public class b
{
  [Key]
  public int id{get;set;}
  
  public a  a_ID {get;set;}
}

public class c
{
  [Key]
  public int id {get;set;}
  
  public b b_id{get;set}
}

the code snippet previously mentioned is the model.

public void Insert(c c1)
{
   db.c.Add(c1);
   db.Entity(c1.b_id).state = Entities.Unchanged;
   db.Entity(c1.b_id.a_id).state = Entities.Unchanged;
   db.SaveChanges();
}

This code snippet previously mentioned is the EF code.

but I get error, because the ef try to update table b in database: update b set a_id = x where id =..../*ignore the follow code*/

Question:

  Why Does Entity Framework generate update clause to update foreign key?

Answer 1

User-707554951 posted

Hi CrazyOldPotato.

From your description and code, you want to add c1 to  c table in database, if that the case. According the relationship between you class(a,b,c). I suggest you could following the steps:

Using the following code to add a1 to database:

using (Model2 context = new Model2())
            {
                a a1 = new a { id = 1 };
                context.a.Add(a1);
                context.SaveChanges();
            }

Then add b1 to database:

using (Model2 context = new Model2())
            {
                a a1 = context.a.Find(1);
                b b1 = new b { id = 1, a_ID = a1 };
                context.b.Add(b1);
                context.SaveChanges();
            }

Finally, you could add c1 to database without any error:

 using (Model2 context=new Model2())
            {           
                b b1 = context.b.Find(1);
                c c1 = new c { b_id = b1 };
                context.c.Add(c1);
                context.Entry(c1.b_id).State = EntityState.Unchanged;
               // context.Entry(c1.b_id.a_ID).State = EntityState.Unchanged; This is not required for us.
                context.SaveChanges();
            }

For I couldn't restored your problem. If you still have problem about this, would you please provide detailed error message for us. So that we could solve your problem timely.

Best regards

Cathy

Answer 2

User-623162908 posted

no ,the EF will generate update clause and send this clause first

Answer 3

User-707554951 posted

Hi CrazyOldPotato,

Are your try the code I provide, it work well in my application without generate any update clause.

the EF will generate update clause and send this clause first

would you please provide us with more information about your error message?

Best regards

Cathy