Hi,

I'm currently designing part of a system that needs is responsible for summarizing information on commission earnings and adjustments from sales and refunds respectively. I decided to model problem with the Account and AccountEntry concepts. The interface of my Account class in C# is roughly,

pulic class Account
{
// The net earned within a period
public Money Balance(DateRange)

public Iterator Sales(DateRange)

public Iterator Adjustments(DateRange)

//We only pay if the partner has meet the minimum earnings
public Bool HasMeetMinimum()

private IList<AccountEntry> _Entries = new List<AccountEntry>()
}


I'm hung up on a few things when I think about implementing the balance method which is just the sum of the account entries that fall within the range.

* I don't want to load all of the entries at once for a given account
because of how many there could be.

* I don't want my account class to have a dependency on data access.
I'm using Nhibernate for persistance.

I wondering if I have my responsibilities are the wrong place. Perhaps I should put the Account methods on a Repository. Or maybe it's possible to lazy load a collection based on the values of fields withing a class?
Your feedback is greatly appreciated.

--
Cheers,
Aeden

Hi aedenj - set your collection of AccountEntry objects to be lazy loaded.

I would create a property called Entries on the Account object (implementation not included):

private IList<AccountEntry> _entries = new List<AccountEntry>();
public IList<AccountEntry> Entries { get; set; }


In the mapping file for the Account object I'd map it with a bag:

<bag name="AccountEntry" lazy="true" ....


Please consult the NH documentation for the complete syntax on a bag.

That way you can access the Account object without loading all the entries.

Cheers,
Thomas

You can make it lazy loaded and if its because you are worried about fetching to many objects when they are initialized you can utilize the batch fetching feature



Youre assumptions about the repository is right on, i excpect that you want some sort of filtering of the collection, and for that you have to use a HQL/Criteria query and this should obviously not be in you model so you need a layer where you can ask for Business entities filled with data from your UI