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TOOBJECT ORIENTED PROGRAMMING WITH C#.NET

Features of Object Oriented Programming:

Any programming language to become as object oriented should follow the following features.

AbstractionEncapsulationInheritancePolymorphism

What is an Abstraction?

It’s a process of Hiding the Implementation but providing the service. There are two types of abstraction available: 1. Data Abstraction2. Functional Abstraction

It is a process of Binding the member variable of a class along with member functions.Encapsulation can be implemented with the help of object and also Access modifiers like Private ,public and Protected etc.

What is an Encapsulation?

What is an Inheritance?

This is process of creating a new class from already existing classIn inheritance process existing class is known as Parent/Base class, newly created class is know as Derived/Child class.In inheritance process, child class will get all the features of Parent/Base class.Main purpose of inheritance is code Re-usability and providing additional functionality/enhancement.

What is Polymorphism?

It’s derived from a Greek word, where poly means many morph means Faces/Behaviors.Types of Polymorphism:There are two types of polymorphism1. Static polymorphism/Compile Time polymorphism

/Early Binding2. Dynamic polymorphism/Run Time polymorphism/late

Binding Static polymorphism is achieved using, Function over

loading, operator over loading. Dynamic polymorphism is achieved by using , Function

overriding.

Class in C# .NET

A class is a collection of things which posses common similarities.

In C#.NET a class is a user defined Data type and is Known as Reference Type.

A class can contain following members in C#.NET

1. Data Fields2. Function3. Constructors4. Destructors5. Properties6. Indexers7. Events

1.Data Fields

It’s used to store the data related to the class. Except Data Fields no other member of a class can store the data.To declare any Data Field, we use the following

Syntax

Access modifier Data type Data Field Name = [Initializing value];

Ex:Public int Empid;

2.FUNCTIONS

Any programming language will have methods.

A named block of code is refer as a Method or subprogram.

It can be either value returning or non value returning.

Syntax[<modifiers>]<type|void><name>([<pram

def’s])

{

statements;

};

Syntax to create a class

Access Modifier class Class Name

Syntax to create an Object

Class Name Object Name=new Class Name([args list])

Constructor name

Ex: Program p= new program() orProgram p;P=new program();

How to open Microsoft visual studio .NET

Open V.S Go to File New project Change the language as C# template as Console application Named return as OOPS Project and the write the following code under the default class program

Class program{//No input and out put Void Text1 () { Console.WriteLine (“first method”); }

// No output but has Input Void Text2 (int x, int y)

{ For (int i=1;i<=y;i++)

Console.writeLine (“{0} *{1}={2}”;x, i, x*i); }

//No Input but has out put String Text3 ()

{Return “third method”;

}//has input and out put

String text4 (string name){

return “Hello” +name;}

//Method with Multiple output parametersVoid Meth1 (int x, int y, ref int a, ref int b) {a=x+y;b=x/y;}Static VoidMain (string [] args){Program p=new program ();p.Text1 (); p.Text2 (5, 10);Console.WriteLine (p.Text3 ());Console.WriteLine (p.Text4 (“venkat”));Int m=0, n=0; //Initialization is mandatoryp.Math1 (100, 50, ref m, ref n);Console.WriteLine (M+” “+n);Int q, r; //Initialization is optionalp.Math2 (100, 50, out q, out r);Console.WriteLine (q+” “+r);Console.Readline ();}}

Constructors

A constructor is a member method of a class which is invoked automatically when an object to the class is created.A constructor name should be same name as class name .A constructor does not have any return type even void also.A constructor is used to keep something ready for the object when it is created .

Syntax[<modifiers>]<Name>([<Param Def’s>]){Statements;}

Example program

Class ConDemo{ConDemo (){Console.WriteLine (“Constructor”);}Void Demo (){Console.writeLine (“Method”);}Static VoidMain (){ConDemo cd1=new ConDemo ();ConDemo cd2=new ConDemo ();ConDemo cd3=cd2;Cd1.Demo (); cd2.Demo (); cd3.demo ();Console.ReadLine ();}}

Add a class ConDemo.cs and write the following code

Constructors are TWO Types1

2

Default Constructor

Parameterized Constructor

A constructor without any parameters is a “Default constructor” which can be defined either by the programmer or will be defined by the compiler provided the class doesn't contain any constructor in it.A constructor with parameters is referred as “parameterized constructor” which can be defined only by a parameters.If at all constructors are parameterized we can send values to the parameters at the time of object creation.

Example programAdd a class Maths.cs and write the following codeClass Maths{Int x, y; //class variablesMaths (int x, int y ) //block variables{This.x=x;This.y=y;}Void Add (){Console.WriteLine(x+y);}Void Sub()Console.WriteLine(x-y);}Void Mul (){Console.WriteLine(x*y);}

Void Div (){Console.WriteLine(x/y);}Static VoidMain (){Maths m=new Maths (100, 50);m.Add (); m.Sub () ;m.Mul();m.Div();Console.ReadLine ();}}

INHERITANCE

The process creating a new class form already existing class.Existing class is known as Parent Class or Base Class.New class is known as Child Class or Derived Class.

Child class will get all the features of parent classCode Reusability and providing additional functionalities

consume

members

class1

Parent child Relation

Syntax

[<Modifiers>] class <C C Name>:<P C Name>

Class Class1{ Members}Class Class2 : Class1{ Consume the parent members here}

Child Class Parent Class

Example program

Add a class class1.cs and write the following code

Class class1{Public class1 (){Console.WriteLine (“class1 constructor”);}Public void Text 1(){Console.writeLine (“Method one”);}Public void Text2(){Console.WriteLine (“Method Two”);}}

Add a class class2.cs and write the following code

Class class2:class1{Public class2 (){Console.writeLine (“class 2 constructor”);}Public void Text3 (){Console.writeLine (“Method Three”);}Static VoidMain (){Class2 c=new class2 ();c.Text1 ();c.Text12 ();c.Text3 ();console.Readline ();}}

Polymorphism

Polymorphism can be implemented with the help of TWO approaches

Over Loading

Overriding

Same name different signatures are called overloading method

Same name and same signature is called overriding method

Example program

Add a class Load demo.cs and write the following code

Class LoadDemo{Public void show (){Console.WriteLine (1);}Public void show (int x){Console.WriteLine (2);}Public void show (string s){Console.WriteLine (3);}

Public void show (int x, string s){Console.WriteLine (4);}Public void show (string s, int x){Console.WriteLine (5);}Static VoidMain (){Load demo obj =new LoadDemo ( );Obj. Show (10);Obj. show (“Hello”);Obj. Show (10,”Hello”);Obj. Show (“Hello”, 10);Console.Readline ();}}}

Properties

A property is a member of a class , used to write the data in the data field and read the data from the data field of a class.A property can never store the data, just used to transfer the data.Properties are members that provide a flexible mechanism to read, write or compute the values of private fields.Properties enable a class to expose a public way of getting and setting values, while hiding implementation or verification code.To perform read and write operations, property can contain two assessors/methods.

Assessors with in the property

Accessor enable data to be accessed easily while still providing the safety and flexibility of methods.

Set Accessor Get Accessor

Set Accessor

Set accessor is used to write the data into the data field.This will contain a default and fixed variable named as “value”.Whenever we call the property to write the data, any data we supply will come and store in value variable by default.

Set{Data File Name=value;}

Get AccessorGet Accessor is used to read the data field, using this accessor we can’t write the data.

Get{Return Data File Name:}

Syntax

Types of properties C#.NET will support three types of Properties.

1 •Read Only Property

2 •Write Only Property

3 •Read Write property

This property is used to read the data from the Data field

It is used to write the data into Data field of a class.

It is used to read the data from the Data field and to write the data in to the Data Field

Access Modifier Data Type property Name{ set { Data Field Name=Value; }}

Access Modifier Data Type Property Name{ get { return data Field Name; }}

Access Modifier Data Type property Name{ set { Data Field Name=Value; } get { return data Field Name; }}

Namespace CAProperties{Class clsEmpolyee{ int EmpId,EAge; Public int PEmpId { set { EmpId=value; } get { return EmpId; } }

Syntax Example

Public int PEAge { set { EAge=Value; } get { return EAge; } }}Class ClsProperty1{ Static void Main(string[] args) { clsEmployee obj1=new clsEmployee(); Console.write(“Enter Employee details:”); Obj1.PEmpId=Concert.ToInt32(Console.ReadLine()); Obj1.PEAge=convert.ToInt32(console.ReadLine()); } }}

Abstract

It is a method with can have only syntax, but no implementation is called Abstract Method.It should be overridden in the Sub Class.It can be used mostly in Distributed Applications (Client/sever applications)

AccessSpecifier abstract Return Type

Method Name(parameters);

Syntax

Public abstract void Hello();Example

Interfaces

In the .NET Framework, interfaces have a special naming convention. All interface name begin with a capital I. Interfaces can have properties as we difference from a class.

1. You cannot create an object of an interface2. An interface does not contain any constructor.3. All methods in an interface are abstract.4. An interface can inherit multiple interfaces.

[<modifiers>] interface<name>

{Abstract member declarations

}

Syntax

Add an interface inter1.cs and write the following code

Interface inter1{ Void Add (int x, int y); Void sub (int x, int y); Void test (); }}Add an interface inter2.cs and write the following codeInterface inter2{ Void Mul (int x, int y); Void Div (int x, int y); Void test (); }}

To implement both the above two interfaces Add a class interclass.cs and write the following code

Class Interclass: Inter1, Inter2{ Public void Add (int x, int y) {Console.Writeline(x+y); }Public void Sub (int x, int y) {Console.Writeline(x-y);}Public void Mul (int x, int y) {Console.Writeline(x*y);}

Public void Div (int x, int y) {Console.Writeline(x/y)}public void Test (){Console.Writeline (“Declared under multiple interfaces”);}Void Inter1.Test (){Console.Writeline (“Method of Interfaced 1”);}Void Inter2.Test (){Console.Writeline (“Method of Interfaced 2”);}

Static Void Main (){Inter class obj= new Inter class ();Obj. Add (100, 45);Obj. Sub (100, 45);Obj. Mul (100, 45);Obj.Div (100, 45);Obj. Test ();Inter1 i1 = obj; Inter i2 = obj;I1.Test (); i2.Test ();Console.ReadLine ();}}

Delegates

It’s used to represent or refer one or more functions.Delegates are user defined types in C#.NET.Delegates in C#.NET are similar to function pointers in C++.It is not a member of a class, but similar to a class.To consume any delegate , we need to create an object to delegate. Delegate is a type that references a method.

The delegate method can be invoked like any other method with parameters and written value.These can be used to define callback methods.There are the backbone for events.

Types of Delegates

There are of two types of Delegates available.a) Single cast delegateb) Multi cast delegate A delegate that represents only function is known as

Single Cast Delegate. A delegate that represents only a more than one functions

is known as Multi Cast Delegate.

To work with Delegate Use the Following Steps:Creating a DelegateInstantiating a DelegateInvoking a Delegate

EX: If we consider a function, like Public Void Add (int a , int b ){Code……}To refer this function, if we want to use the Delegate, we use the following steps like…..

STEP 1 Creating A Delegate

Access modifier delegate return type Delegate name([arguments list])EX: public delegate void sampleDelegate(int x, int y)

Syntax

STEP 2 Instantiating a Delegate

Delegate name object name = new Delegate name (Target function name);

EX: SampleDelegate obj=new SampleDelegate(Add);

STEP 3 Invoking a Delegate

Object Name([Arguments Values])

EX: Obj(10,20)

Syntax

Syntax

Add a class del.cs and write the following the codeClass Delclass{ Public String SayHello(string name0 { Return “Hello” +name; }Public delegate string SayDel(String name);Static void Main() {Delclass obj=new Delclass();SayDel Sd=new SayDel(obj.sayHellow);Console.WriteLine(Sd(“xxx”));Console.WrireLine(Sd(“yyy”));Console.WrireLine(Sd(“zzz”));Console.ReadLine(); }}

Program