CODEWITHSUNDEEP
entity-framework
ehsan
ehsan

Reputation: 13

entity framework wrong order of child object after some child objects detached

my problem is after first child object detached and then i add another child object to my parentObj the order of attached child is not correct , my code look like this:

parentObj= new TparentObj();
firstChildObj=new Tchild1();
secondChildObj= new Tchild1();
thirdChildObj=new Tchild1();

parentObj.Tchild1.add(firstChildObj);
parentObj.Tchild1.add(secondChildObj);
// now parentObj.Tchild1.first()==firstChildObj return true
///then for some reason
parentObj.Tchild1.remove(firstChildObj);
db.Entry(firstChildObj).State = EntityState.Detached;

// now i add third childObj  
parentObj.Tchild1.add(thirdChildObj);
//// now parentObj.Tchild1.first()==thirdChildObj return true!!

after saved db the result in database is Correct; but how can i get list of childObj in order they added?

Upvotes: 0

Views: 184

Answers (1)

Jcl
Jcl

Reputation: 28272

Entity Framework by default uses HashSets for its collections. HashSet doesn't take ordering into account.

You shouldn't rely on the ordering of elements for it. The current implementation seems (as you are experiencing) to add the element on the first unused position (in your case, the removed one), but this is an implementation detail and you shouldn't rely on it.

About HashSet, the MSDN says about it (bold is mine):

The HashSet class provides high-performance set operations. A set is a collection that contains no duplicate elements, and whose elements are in no particular order.

and

A HashSet collection is not sorted and cannot contain duplicate elements. If order or element duplication is more important than performance for your application, consider using the List class together with the Sort method.

Upvotes: 1

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