Using Business Logic

Using Business Logic

To help not only with versioning, but also with designing a loosely coupled system, try as much as possible to write code that is independent of the actual wire format. Listing 15.4 shows an example that creates a PurchaseOrderHandler class which uses a PurchaseOrder object. However, the service takes a NewPurchaseOrder class that is designed to match the wire format.

Changing the Wire Format

public class Service1 : WebService
{
     [WebMethod]
     public POReceipt SubmitPO(NewPurchaseOrder po)
     {
     PurchaseOrder purchaseOrder = new PurchaseOrder();
     purchaseOrder.Details = po.SomethingInteresting;

     POReceipt receipt = new POReceipt();
     receipt.ticket = PurchaseOrderHandler.HandleOrder(
                                        purchaseOrder );
     return receipt;
     }
}
[XmlRoot(
     "PurchaseOrder",
     Namespace="http://keithba.com/2002/05/PurchaseOrder")]
public class NewPurchaseOrder
{
     public String SomethingInteresting;
}

public class PurchaseOrder
{
     public String Details;
}

public class POReceipt
{
      [XmlAttribute]
      public int ticket;
}

public class PurchaseOrderHandler
{
     public static int HandleOrder( PurchaseOrder po )
     {
          //insert real business logic here
     }
}

This allows you to deal with changes to wire format that may occur without having to change your core business logic. Instead, the ASP.NET Web Service is a thin shell over the core business logic.