oops concept,Abstraction,Encapsulation,Inheritance: 2012

Friday, 18 May 2012

Introduction to WCF - WCF tutorial | WCF Tutorial - Windows Communication Foundation | WCF Example | WCF Sample code in asp.net 3.5 | Basic WCF Tutorial for Beginners

Introduction:

Here I will explain what WCF (windows communication foundation) is, uses of windows communication foundation and how to create and use windows communication foundation in c#.

Description:

In previous articles explained clearly what webservice is and how to create and consume webservice using asp.net . In another post I explained clearly what windows service is and how to create windows service and sample of windows service using c#. Now in this article I will explain about windows communication foundation. First we will see what a WCF (window communication foundation) is and uses of WCF (windows communication foundation) after that we will see how to create and use WCF in c#.net.

What is WCF (windows communication foundation) Service?

Windows Communication Foundation (Code named Indigo) is a programming platform and runtime system for building, configuring and deploying network-distributed services. It is the latest service oriented technology; Interoperability is the fundamental characteristics of WCF. It is unified programming model provided in .Net Framework 3.0. WCF is a combined feature of Web Service, Remoting, MSMQ and COM+. WCF provides a common platform for all .NET communication.

Advantages of WCF

1) WCF is interoperable with other services when compared to .Net Remoting where the client and service have to be .Net.

2) WCF services provide better reliability and security in compared to ASMX web services.

3) In WCF, there is no need to make much change in code for implementing the security model and changing the binding. Small changes in the configuration will make your requirements.

4) WCF has integrated logging mechanism, changing the configuration file settings will provide this functionality. In other technology developer has to write the code.

Difference between WCF and Web service

Web service is a part of WCF. WCF offers much more flexibility and portability to develop a service when comparing to web service. Still we are having more advantages over Web service; following table provides detailed difference between them.

Features	Web Service	WCF
Hosting	It can be hosted in IIS	It can be hosted in IIS, windows activation service, Self-hosting, Windows service
Programming	[WebService] attribute has to be added to the class	[ServiceContract] attribute has to be added to the class
Model	[WebMethod] attribute represents the method exposed to client	[OperationContract] attribute represents the method exposed to client
Operation	One-way, Request- Response are the different operations supported in web service	One-Way, Request-Response, Duplex are different type of operations supported in WCF
XML	System.Xml.serialization name space is used for serialization	System.Runtime.Serialization namespace is used for serialization
Encoding	XML 1.0, MTOM(Message Transmission Optimization Mechanism), DIME, Custom	XML 1.0, MTOM, Binary, Custom
Transports	Can be accessed through HTTP, TCP, Custom	Can be accessed through HTTP, TCP, Named pipes, MSMQ,P2P, Custom
Protocols	Security	Security, Reliable messaging, Transactions

A WCF Service is composed of three components parts viz,

1) Service Class - A WCF service class implements some service as a set of methods.

2) Host Environment - A Host environment can be a Console application or a Windows Service or a Windows Forms application or IIS as in case of the normal asmx web service in .NET.

3) Endpoints - All communications with the WCF service will happen via the endpoints. The endpoint is composed of 3 parts (collectively called as ABC's of endpoint) as defines below:

Address: The endpoints specify an Address that defines where the endpoint is hosted. It’s basically url.

Ex:http://localhost/WCFServiceSample/Service.svc

Binding: The endpoints also define a binding that specifies how a client will communicate with the service and the address where the endpoint is hosted. Various components of the WCF are depicted in the figure below.

"A" stands for Address: Where is the service?
"B" stands for Binding: How can we talk to the service?
"C" stands for Contract: What can the service do for us?

Different bindings supported by WCF

Binding	Description
BasicHttpBinding	Basic Web service communication. No security by default
WSHttpBinding	Web services with WS-* support. Supports transactions
WSDualHttpBinding	Web services with duplex contract and transaction support
WSFederationHttpBinding	Web services with federated security. Supports transactions
MsmqIntegrationBinding	Communication directly with MSMQ applications. Supports transactions
NetMsmqBinding	Communication between WCF applications by using queuing. Supports transactions
NetNamedPipeBinding	Communication between WCF applications on same computer. Supports duplex contracts and transactions
NetPeerTcpBinding	Communication between computers across peer-to-peer services. Supports duplex contracts
NetTcpBinding	Communication between WCF applications across computers. Supports duplex contracts and transactions
BasicHttpBinding	Basic Web service communication. No security by default
WSHttpBinding	Web services with WS-* support. Supports transactions

Contract: The endpoints specify a Contract that defines which methods of the Service class will be accessible via the endpoint; each endpoint may expose a different set of methods.

Different contracts in WCF

Service Contract

Service contracts describe the operation that service can provide. For Eg, a Service provide to know the temperature of the city based on the zip code, this service is called as Service contract. It will be created using Service and Operational Contract attribute.

Data Contract

Data contract describes the custom data type which is exposed to the client. This defines the data types, which are passed to and from service. Data types like int, string are identified by the client because it is already mention in XML schema definition language document, but custom created class or data types cannot be identified by the client e.g. Employee data type. By using DataContract we can make client to be aware of Employee data type that are returning or passing parameter to the method.

Message Contract

Default SOAP message format is provided by the WCF runtime for communication between Client and service. If it is not meeting your requirements then we can create our own message format. This can be achieved by using Message Contract attribute.

Fault Contract

Suppose the service I consumed is not working in the client application. I want to know the real cause of the problem. How I can know the error? For this we are having Fault Contract. Fault Contract provides documented view for error occurred in the service to client. This helps us to easy identity, what error has occurred.

Overall Endpoints will be mentioned in the web.config file for WCF service like this

<system.serviceModel>

</identity>

</endpoint>

</service>

</services>

</behavior>

</serviceBehaviors>

</behaviors>

</system.serviceModel>

Creating simple application using WCF

First open Visual Studio and click file --> Select New --> Website Under that select WCF Service and give name for WCF Service and click OK

Once you created application you will get default class files including Service.cs and IService.cs

Here IService.cs is an interface it does contain Service contracts and Data Contracts and Service.cs is a normal class inherited by IService where you can all the methods and other stuff.

Now open IService.cs write the following code

[ServiceContract]

public interface IService

{

[OperationContract]

string Welcome(string Name);

}

After that open Service.cs class file and write the following code

public class Service : IService

{

public string SampleMethod(string Name)

{

return "First WCF Sample Program " + Name;

}

Here we are using basicHttpBinding for that our web.config file system.serviceModel code should be like this and I hope no need to write any code because this code already exists in your web.config file in system.serviceModel

<system.serviceModel>

</identity>

</endpoint>

</service>

</services>

</behavior>

</serviceBehaviors>

</behaviors>

</system.serviceModel>

Our WCF service ready to use with basicHttpBinding. Now we can call this WCF Service method console applications

After completion of WCF service creation publish or deploy your WCF Service in your system. If you don’t’ have idea on deploy check this post publish or deploy website

After completion of deploy webservice now we can see how to use WCF Service in our console application

Calling WCF Service using Console Application

To call WCF service we have many ways like using console app, windows app and web app but here I am going for console application.

Create new console app from visual studio select project type as console application gives some name as you like.

After Creation Console application now we need to add WCF reference to our console application for that right click on your windows application and select Add Service Reference

Now one wizard will open in that give your WCF service link and click Go after add your service click OK button.

After completion of adding WCF Service write the following code in Program.cs class file Main method

static void Main(string[] args)

{

ServiceReference1.ServiceClient objService = new ServiceClient();

Console.WriteLine("Please Enter your Name");

string Message = objService.SampleMethod(Console.ReadLine());

Console.WriteLine(Message);

Console.ReadLine();

}

After that open your app.config file and check your endpoint connection for WCF Service reference that should be like this

<endpoint address=" http://localhost/WCFServiceSample/Service.svc"

binding="wsHttpBinding" bindingConfiguration="WSHttpBinding_IService"

contract="ServiceReference1.IService" name="WSHttpBinding_IService">

</identity>

</endpoint>

Now everything is ready run your application that output should be like this

OOPS : Abstraction, Encapsulation, Inheritance, Polymorphism

OOPS Features

* The object oriented programming (OOP) is a programming model

where Programs are organized around object and data rather than

action and logic.

* OOP allow decomposition of a problem into a number of entities called

Object and then builds data and function around these objects.

The Program is divided into number of small units called Object. The data and function are build around these objects.
The data of the objects can be accessed only by the functions associated with that object.
The functions of one object can access the functions of other object.

OOP has the following important features.

Class:

A class is the core of any modern Object Oriented Programming language such as C#.

In OOP languages it is must to create a class for representing data.

Class is a blueprint of an object that contains variables for storing data and functions to performing operations on these data.

Class will not occupy any memory space and hence it is only logical

representation of data.

To create a class, you simply use the keyword "class" followed by the class name:

class Employee

{

}

Object:

Objects are the basic run-time entities in an object oriented system.They may represent a person,a place or any item that the program has to handle.

"Object is a Software bundle of related variable and methods. "

“Object is an instance of a class”

Class will not occupy any memory space. Hence to work with the data represented by the class you must create a variable for the class, which is called as an object.

When an object is created by using the keyword new, then memory will be allocated for the class in heap memory area, which is called as an instance and its starting address will be stored in the object in stack memory area.

When an object is created without the keyword new, then memory will not be allocated in heap I.e. instance will not be created and object in the stack contains the value null.

When an object contains null, then it is not possible to access the members of the class using that object.

class Employee

{

}

Syntax to create an object of class Employee:-

Employee objEmp = new Employee();

All the programming languages supporting object oriented Programming will be supporting these three main concepts:

Encapsulation
Inheritance
Polymorphism

Abstraction:

Abstraction is "To represent the essential feature without representing the back ground details."

Abstraction lets you focus on what the object does instead of how it does it.

Abstraction provides you a generalized view of your classes or object by providing relevant information.

Abstraction is the process of hiding the working style of an object, and showing the information of an object in understandable manner.

Real world Example of Abstraction: -

Suppose you have an object Mobile Phone.

Suppose you have 3 mobile phones as following:-

Nokia 1400 (Features:- Calling, SMS)

Nokia 2700 (Features:- Calling, SMS, FM Radio, MP3, Camera)

Black Berry (Features:-Calling, SMS, FM Radio, MP3, Camera, Video Recording, Reading E-mails)

Abstract information (Necessary and Common Information) for the object "Mobile Phone" is make a call to any number and can send SMS."

so that, for mobile phone object you will have abstract class like following:-

abstract class MobilePhone

{

public void Calling();

public void SendSMS();

}

public class Nokia1400 : MobilePhone

{

}

public class Nokia2700 : MobilePhone

{

public void FMRadio();

public void MP3();

public void Camera();

}

public class BlackBerry : MobilePhone

{

public void FMRadio();

public void MP3();

public void Camera();

public void Recording();

public void ReadAndSendEmails();

}

Abstraction means putting all the variables and methods in a class which are necessary.

For example: - Abstract class and abstract method.

Abstraction is the common thing.

example:

If somebody in your collage tell you to fill application form, you will fill your details like name, address, data of birth, which semester, percentage you have got etc.

If some doctor gives you an application to fill the details, you will fill the details like name, address, date of birth, blood group, height and weight.

See in the above example what is the common thing?

Age, name, address so you can create the class which consist of common thing that is called abstract class.

That class is not complete and it can inherit by other class.

Encapsulation:

Wrapping up data member and method together into a single unit (i.e. Class) is called Encapsulation.

Encapsulation is like enclosing in a capsule. That is enclosing the related operations and data related to an object into that object.

Encapsulation is like your bag in which you can keep your pen, book etc. It means this is the property of encapsulating members and functions.

class Bag

{

book;

pen;

ReadBook();

}

Encapsulation means hiding the internal details of an object, i.e. how an object does something.

Encapsulation prevents clients from seeing its inside view, where the behaviour of the abstraction is implemented.

Encapsulation is a technique used to protect the information in an object from the other object.

Hide the data for security such as making the variables as private, and expose the property to access the private data which would be public.

So, when you access the property you can validate the data and set it.

Example:

class Demo

{

private int _mark;

public int Mark

{

get { return _mark; }

set { if (_mark > 0) _mark = value; else _mark = 0; }

}

Real world Example of Encapsulation:-

Let's take example of Mobile Phone and Mobile Phone Manufacturer

Suppose you are a Mobile Phone Manufacturer and you designed and developed a Mobile Phone design(class), now by using machinery you are manufacturing a Mobile Phone(object) for selling, when you sell your Mobile Phone the user only learn how to use the Mobile Phone but not that how this Mobile Phone works.

This means that you are creating the class with function and by making object (capsule) of it you are making availability of the functionality of you class by that object and without the interference in the original class.

Example-2:

TV operation

It is encapsulated with cover and we can operate with remote and no need to open TV and change the channel.

Here everything is in private except remote so that anyone can access not to operate and change the things in TV.

Inheritance:

When a class acquire the property of another class is known as inheritance.

Inheritance is process of object reusability.

For example, A Child acquire property of Parents.

public class ParentClass

{

public ParentClass()

{

Console.WriteLine("Parent Constructor.");

}

public void print()

{

Console.WriteLine("I'm a Parent Class.");

}

public class ChildClass : ParentClass

{

public ChildClass()

{

Console.WriteLine("Child Constructor.");

}

public static void Main()

{

ChildClass child = new ChildClass();

child.print();

}

Output:

    Parent Constructor.
    Child Constructor.
    I'm a Parent Class.

Polymorphism:

Polymorphism means one name many forms.

One function behaves different forms.

In other words, "Many forms of a single object is called Polymorphism."

Real World Example of Polymorphism:

Example-1:

A Teacher behaves to student.

A Teacher behaves to his/her seniors.

Here teacher is an object but attitude is different in different situation.

Example-2:

Person behaves SON in house at the same time that person behaves EMPLOYEE in office.

Example-3:

Your mobile phone, one name but many forms

As phone
As camera
As mp3 player
As radio

To Read Polmorphism in Detail click following link:-

Polymorphism in .Net

Difference between Abstraction and Encapsulation :-

Abstraction	Encapsulation
1. Abstraction solves the problem in the design level.	1. Encapsulation solves the problem in the implementation level.
2. Abstraction is used for hiding the unwanted data and giving relevant data.	2. Encapsulation means hiding the code and data into a single unit to protect the data from outside world.
3. Abstraction lets you focus on what the object does instead of how it does it	3. Encapsulation means hiding the internal details or mechanics of how an object does something.
4. Abstraction- Outer layout, used in terms of design. For Example:- Outer Look of a Mobile Phone, like it has a display screen and keypad buttons to dial a number.	4. Encapsulation- Inner layout, used in terms of implementation. For Example:- Inner Implementation detail of a Mobile Phone, how keypad button and Display Screen are connect with each other using circuits.

The easier way to understand Abstraction and encapsulation is as follows:-

Real World Example:-

Take an example of Mobile Phone:-

You have a Mobile Phone, you can dial a number using keypad buttons. Even you don't know how these are working internally. This is called Abstraction. You have the only information that is needed to dial a number. But not its internal working of mobile.

But how the Mobile Phone internally working?, how keypad buttons are connected with internal circuit? is called Encapsulation.