Create new Entity with children

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Hi everyone

I'm going postal for this :)

given two entities:

C#

public class parent{
    int parentid {get;set;}
    public virtual ICollection<child> childre{get; set;}
}

public class child{
    int childid{get;Set;}
    public virtual parent parent{get;set;}
}</child>

can I do something like

C#

public actionresult create(parent parent){
 
  child newchild = new (child);
  parent.children.add(child); 
  context.parent.add(parent);
}

should'nt this create the parent entity with added child(children)? How can I do this?

do I have to do it separately???

C#

public actionresult create(parent parent){
 
  child newchild = new (child);

  context.parent.add(parent);

  child.parent=parent;
  context.child.add(child);
}

Thank you in advance,

Alberto.

Posted 3-Dec-11 1:40am

Alberto Biasiutti

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2 solutions

Solution 1

The code below should fix what you are trying to do. There were only a couple of typo's in the code every thing else looked good.

C#

public class parent{
    int parentId {get;set;}
    public virtual ICollection<child> children{get; set;}
}
 
public class child{
    int childId{get;Set;}
    public virtual parent childParent{get;set;}
}

public actionresult create(parent parent){
 
  child newchild = new child();
  parent.children.add(newchild); 
  context.parent.add(parent);
  return View(parent);
}

</child>

Posted 3-Dec-11 10:29am

GateKeeper22

Comments

Alberto Biasiutti 4-Dec-11 15:54pm

Thank you GK... the typo's were not the problem (I wrote the question VEEERY quickly because I was in hurry).. thank you any way, I'll post the solution my boss foundout.

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Alberto Biasiutti · Accepted Answer · 2011-12-05T03:03:00

First of all, I apologize: I asked the question whitout being precise. The problem was that, when calling the create function, it gave a null reference exeption on parent.children.add(child):

C#

public actionresult create(parent parent){
 
  child newchild = new (child);
  parent.children.add(child);  /*<-- Null Reference exeption*/
  context.parent.add(parent);
}

The actual problem was that, before the parent is created, the ICollection<child> doesn't exists. It is sufficient to instantiate it before adding elements to it.

this way it works, automatically adding both the parent and the child entities (in the previous example, I also forgot about the context.SaveChanges() instruction to actually save the objects to database):

C#

public actionresult create(parent parent){
 
  child newchild = new (child);
  parent.children=new List<child>();
  parent.children.add(child);
  context.parent.add(parent);
  context.SaveChanges();
}</child>

I have a little doubt about the correctness of setting an ICollection to a new List, so if anyone has a better or more correct approach, any suggestion is welcome.