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302 Microsoft Visual Studio 2010: A Beginner’s Guide
The WCF Service Library starts with two files with default names of IService1.cs
(IService1.vb for VB) and Service1.cs (Service1.vb for VB), which contain an interface
and a class that implements that interface. If you need to brush up on interfaces, review
Chapter 4 because an interface is an integral part of WCF development.
Specifying a Contract with WCF Interfaces
The IService1.cs (IService1.vb in VB) class in Figure 11-1 contains an interface.
As you learned in Chapter 4, interfaces define a set of members that do not have
implementations. The actual implementation will be provided by classes that implement
the interface. You can consider the interface to be a contract that guarantees a set of
operations for a service. In addition to the interface, the types associated with the service
are part of the service contract. The contract is important because when you write code
that uses the Web service, it is the contract that your code will see and everything that is
not in the contract will not be visible. Any application wishing to use a Web service will
make calls to the Web service based on what is specified in the contract. In this section,
you’ll see how to define a WCF contract with an interface, built-in types, and custom
types. Later sections will show how to implement and consume the contract, bringing
the importance of the contract full circle so that you can see how the contract is defined,
implemented, and consumed.
Examining the VS-Generated Contract
You really don’t want to work with an interface named IService1; it doesn’t mean anything.
So, rename IService1.cs to ICustomerService.cs (IService1.vb to ICustomerService.vb for
VB), because it will be configured to manage customer records. You’ll receive a message
box for renaming the code, and you should respond affirmatively. When you open the
ICustomerService.cs file, you’ll see the same code as Listing 11-1, containing an interface
and attributes for defining the ICustomerService contract.
Listing 11-1 A WCF service interface
using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.Text;
namespace WcfDemoCS