WCF - how can I define services in a more object-oriented way?

Question

What is the best way to access a remote object model over WCF?

I have one system layer (A) with an object-oriented model and want to access this model from another layer (B)

The required objects should be loaded by B on-demand. As an example, suppose I have classes C1 and C2 with C1 holding a List of C2. This list should be loaded only when it is accessed.

Since data contracts cannot hold operation contracts, I would implement this with one service contract with two methods "getC1" and "getListC2(C1)"

But, what I actually want is to access an object-oriented model, e.g. call a function on C1: C1.getListC2

How can I work with WCF in a more object-oriented way?

Service oriented architectures (and especially WCF) and object-oriented principles don't always match very well. SOA is about services and messages - typically concrete things. It doesn't really care much about inheritance and polymorphism, really - it needs to have and deal with concrete message objects. OOP on the other hand is a lot about encapsulation, inheritance, polymorphism. OOP **within** a service (implementation) works great - OOP across service boundaries less so.... — marc_s, Mar 26 '12 at 15:35
To add to what @marc_s has said, what you're talking about (and what the answer advocates) is using a relatively [Fine Grained Facade](http://martinfowler.com/eaaCatalog/remoteFacade.html) on a remote service. You should be wary of how well this will perform, and be pragmatic about choosing which OO techniques you apply when working across a remote boundary. — Steve Wilkes, Mar 28 '12 at 09:57

RQDQ · Accepted Answer · 2012-03-26T14:01:02.960

One way to approach this is to wrap the proxy objects with your own lazy loading (and other) business logic. In other words, let's say you have a WCF proxy called Order and a service method GetOrderLineItems().

public class Order
{
    private Proxies.Order _order;
    private List<OrderLineItem> _lineItems;

    public string Name 
    {
        get { return _order.Name; }
    }

    public List<OrderLineItem> LineItems
    { 
        if (_lineItems == null)
        {
             _lineItems = //Make the service call to get these objects
        }
    }
}

Another way to synthesize this is to add extension methods to your proxy objects:

public static List<Proxies.OrderLineItem> GetLineItems(this Proxies.Order order)
{
     //Make the service call to get the line items
}

Which would allow you to do:

var lineItems = order.GetLineItems();

Thanks! I like the approach with extension methods! – Max Mar 27 '12 at 08:46 — Max, Mar 27 '12 at 08:46

WCF - how can I define services in a more object-oriented way?

1 Answers1