Let's study a sample project using XML web services with VS 2008, and create a service interface for our Order Management System. We will perform the following:
1. Use the 5-tier solution we created in Chapter 4.
2. Create a service interface around it using XML web services in an SOA-like fashion.
3. Allow the GUI to talk to this interface instead of using the business layer directly.
Note
We can also use the sample code created in Chapter 5 using MVC. MVC and SOA complement each other, and one should not get confused with the question, "should I use MVC or SOA?" MVC has a purpose different from that of SOA, and can be used in any SOA implementation.
In this example, our main aim is to see how a service interface can provide another level of abstraction between the GUI and BL/DAL tiers, and enable our project to talk to multiple clients (or GUIs) using XML web services. Let's look at a simple example that illustrates how loose coupling can be implemented.