How To Program WCF

There is so much to understand and so many classes for WCF, but fortunately programming for WCF is streamlined.

1. Object Oriented vs Service Oriented
Before we get into some programming syntax, let us look at what will be different for us as traditional OO (Object Oriented) programmers to get into the SO (Service Oriented) mode.

Object Oriented - Classes and Interfaces are the norm. Two Libraries dependent on each other communicating via dstributed object calls. Hence OO is a tightly coupled way to develop applications.

Service Oriented - Classes and Interfaces are still in use but there is decoration of WCF classes by attributes like ServiceContract, OperationContract. Since the application components and services are connected via messaging mechanism (passing messages) across different platforms, it is called loosely coupled.

e.g. A School Service:

[ServiceContract]
SchoolService
{
[OperationContract]
double CalculateStudentFee()
{
...
}
}

2. Understanding Service Model in WCF

Most of the functionality is provided by System.ServiceModel Namespace. A WCF Service Provides functionality/operations to other services or applications and consists of one or more End Points. Each End Point, in turn, consists of Address, Bindings and Contracts.

Address --> Where the service resides.

Binding --> How the service communicates, Protocols etc.

Contracts --> What the Service does, What it provides.

e.g. of System.ServiceModel Classes

NetTcpBinding, BasicHttpBinding, ChannelFactory, Identity (For Identification as messages are exchanged between End Points), ServiceHost (To Provide a Host).

e.g. of System.ServiceModel.Channels

These classes are used in communication between EndPoints. Some of the examples are as follows:

AddressHeader, MessageHeader, Binding (Collection of BindingElements used for specifying communications for each End Point), BindingElement, BindingContext.

Transactions

As with any other context, ACID Properties define a transaction i.e. Atomicity, Consistency, Isolation and Durability. There is a Namespace called System.Transactions which has couple of classes in it:

--> Lightweight Transaction Manager (LM)

--> OLETx Transaction Manager

As a final note, WCF allows passing transactions from Client to server.

Lets look at a code example and some explanation to understand the basic constructs of WCF programming:

[CODE EXAMPLE]

3. svcutil.exe

This is a utiltiy which will be used a fair bit in our strides into WCF programming. This generates service code from metadata docs and metadata from service code. Many switches/options for metadata generation, code generation and serialization etc. are available. In general svcutil syntax is as follows:

svcutil [options][metadatapath|assemblypath|metadataurl]

4. WCF Programming Methods

There are several ways to do WCF Programming. One or a combination of them could be used. In the next series of articles, Let's have a look at them one by one.