Mapping a collection-derived entity

Question

Being new to the EF, I couldn't even search old posts for the solution -- I have no idea what this technique may be called. Nevertheless, here's what I got.

The data model has 2 tables -- Contacts and PhoneNumbers with a 1-to-many relationship:
 Contacts
 - ContactId
 - Name
 
 PhoneNumbers
 - PhoneNumberId
 - ContactId
 - PhoneNumber

Naturally, I'd like to have Contact and PhoneNumber entities. The straightforward approach, as I understand, is to have a Contact class containing a reference to a collection of PhoneNumber(s):

class Contact
{
   public PhoneNumber [] PhoneNumbers {get;set;}
}

Is it possible to somehow replace PhoneNumber []  with MyPhoneNumbersCollection? I would like to have some logic implemented that deals with phone numbers in the context of a given Contact (for instance, find all phone numbers that satisfy some rules, etc.). So, ultimately, the domain model would contain a 3rd entity (is it even appropriate to call it an entity) called MyPhoneNumbersCollection, and the Contact class would be:

class Contact
{
   public MyPhoneNumbersCollection PhoneNumbers {get;set;}
}

Any help / suggestions are greatly appreciated.

---

Regards, VRSki

Answer 1

In EF3.5 you cannot do this because EF 3.5 doesn't support POCO, meaning the designer builds the entity classes for you. In the case of collections the generated type is EntityCollection<T>.

You can perhaps create extension methods for the EntityCollection type that will work on specific generic types, for example:

public static bool IsPhoneExists(this EntityCollection<PhoneNumber> phones, PhoneNumber targetPhone)
{
...
}

And call it by:
Contact c;
c.PhoneNumbers.IsPhoneExists(p);

In EF 4 you can build POCO classes but I'm unsure to whether you can change the type of collection (if so, it will only be by editing the template). You might be able to do it easly if you work with code-only mode. You'd better check with the EF4 forum if it interests you
http://social.msdn.microsoft.com/Forums/en-US/adonetefx

---

Please mark posts as answers/helpful if it answers your question

Answer 2

Thank you.

---

Regards, VRSki