Repository Pattern without an ORM

Question

I am using repository pattern in a .NET C# application that does not use an ORM. However the issue I am having is how to fill One-to-many List properties of an entity. e.g. if a

Answer 1

Another possible answer is to create a new Proxy object that inherits from Customer, call it CustomerProxy, and handle the lazy load there. All this is pseudo-code, so it's to give you an idea, not just copy and paste it for use.

Example:

public class Customer
{
    public id {get; set;}
    public name {get; set;}
    etc...
    public virtual IList Orders {get; protected set;}
}

here is the Customer "proxy" class... this class does not live in the business layer, but in the Data Layer along with your Context and Data Mappers. Note that any collections you want to make lazy-load you should declare as virtual (I believe EF 4.0 also requires you to make props virtual, as if spins up proxy classes at runtime on pure POCO's so the Context can keep track of changes)

internal sealed class CustomerProxy : Customer
{
   private bool _ordersLoaded = false;
    public override IList Orders
    {
        get
        {
            IList orders = new List();
            if (!_ordersLoaded)
            {
                //assuming you are using mappers to translate entities to db and back
                //mappers also live in the data layer
                CustomerDataMapper mapper = new CustomerDataMapper();
                orders = mapper.GetOrdersByCustomerID(this.ID);
                _ordersLoaded = true;

                // Cache Cases for later use of the instance
                base.Orders = orders;
            }
            else
            {
                orders = base.Orders;
            }
            return orders;
        }
   }
}

So, in this case, our entity object, Customer is still free from database/datamapper code calls, which is what we want... "pure" POCO's. You've delegated the lazy-load to the proxy object which lives in the Data layer, and does instantiate data mappers and make calls.

there is one drawback to this approach, which is calling client code can't override the lazy load... it's either on or off. So it's up to you in your particular usage circumstance. If you know maybe 75% of the time you'll always needs the Orders of a Customer, than lazy-load is probably not the best bet. It would be better for your CustomerDataMapper to populate that collection at the time you get a Customer entity.

Again, I think NHibernate and EF 4.0 both allow you to change lazy-loading characteristics at runtime, so, as per usual, it makes sense to use an ORM, b/c a lot of functionality is provided for you.

If you don't use Orders that often, then use a lazy-load to populate the Orders collection.

I hope that this is "right", and is a way of accomplishing lazy-load the correct way for Domain Model designs. I'm still a newbie at this stuff...

Mike