Microsoft's next-generation programming platform and runtime system for building, configuring and deploying service-oriented applications. It enables developers to build secure, reliable, transacted solutions that integrate across platforms and interoperate with existing investments. Most of the WCF functionality is included in a single assembly called System.ServiceModel.dll, located in the System.ServiceModel namespace.

What are the ABCs of WCF?

ABC stands for address, binding, and contract, they are also called WCF endpoint.

• A - stands for Address: Where is the service?
• B - stands for Binding: How do I talk to the service?
• C - stands for Contract: What can the service do for me?

Address:  The address provides two important elements: the location of the service, and the transport protocol.

WCF supports the following transport schemas:

• HTTP

• TCP

• Peer network

• IPC (Inter-Process Communication)

• MSMQ

Here are few sample addresses.

http://localhost:8001

http://localhost:8001/TestService

net.tcp://localhost:8004/TestService

net.pipe://localhost/TestPipe

net.msmq://localhost/private/TestQueue

Binding: Bindings are objects that are used to specify the communication details that are required to connect to the endpoint of a WCF service. It is the primary extension point of the ABCs of WCF. Bindings describe the transport protocol, message-encoding format and other messaging protocols for the communication channel. Here are complete list of the standard bindings that come with WCF.

Bindings can be defined in two ways:

• Declaratively, using service model configuration settings, Here is a declaratively sample:

  <endpoint address="http://localhost:8001/TestService"
  binding="basicHttpBinding" contract="ITestService" />

• Programmatically, by adding endpoints to the ServiceHost, Here is a programmatically sample:

  BasicHttpBinding binding = new BasicHttpBinding();
  binding.Security.Mode = BasicHttpSecurityMode.None;
  Uri baseAddress = new Uri("http://localhost:8001/TestService");
  Uri address = new Uri("http://localhost:8001/TestService/TestService");
  ServiceHost serviceHost = new ServiceHost(typeof(TestService), baseAddress);
  serviceHost.AddServiceEndpoint(typeof(ITestService), binding, address);

  In programmatically, As you can see we construct a binding instance and assign its endpoints.
  

 Contract: A contract is a description of the messages that are passed to and from service endpoints.

There are three types of contracts in WCF:

• Service contracts: Describe which operations the client can perform on the service. It defines some properties about the service, and a set of actions called Operation Contracts. Operation Contracts are equivalent to web methods in ASMX technology. Here is a sample of service contract.

  <%\@ ServiceHost Language="C#" Service="TestService" %>
  using System.ServiceModel;
  [ServiceContract]
  public interface ITestInterface
  {
   [OperationContract]
   string Test ( string message);
  }
  public class TestService : ITestInterface
  {
   public string Test ( string message)
   {
     return "Hello: " + message;
   }
  }

• Data contracts: Data contracts describe data structures that are used by the service to communicate with clients. A data contract maps CLR types to XML Schema Definitions (XSD) and defines how they are serialized and deserialized. Data contracts describe all the data that is sent to or from service operations.

  [DataContract]
  class TestDataContract
  {
   [field:DataMember]
   public event EventHandler TestEvent;
  }

• Message contracts: Message contracts describe the structure of SOAP messages sent to and from a service and enable you to inspect and control most of the details in the SOAP header and body.

      [MessageContract]
      public class BidPrice
      {
          [MessageHeader]
          public DateTime CurrentTime;
          [MessageBodyMember]
          public Price Price;
      }

References:

• MSDN
• Essential Windows Communication Foundation (WCF): For .NET Framework 3.5
• Pro WCF

Summary