Question

i wanna add and an entity and get its identity before savechanges() and set it as a foreign key of another entity before savechanges in entity framework code first. is it possible?

first model

  public class A
{ 
   int AId { get; set; }
   string name { get; set; }
 }

second model

  public class B
{ 
   int BId { get; set; }
   int AId { get; set; }
   string name { get; set; }
 }

and…..

 db.As.Add(A);
 b.AId = A.Aid;
 db.savechanges();

is there any article which explains how it works?

Answer 1

Declare a property of type A in B.

public class A
{ 
   int AId { get; set; }
   string name { get; set; }
}

public class B
{ 
   int BId { get; set; }

   virtual A A { get; set; }
   int AId { get; set; }

   string name { get; set; }
}

Then assign the instance of A to that navigational property. EF will determine the insert/update order of entities resolve the FKs.

 b.A = a;
 db.As.Add(a);
 db.savechanges();