oops csharp

8/9/2019 OOPs CSharp

1/43

OOPs

Object Oriented ProgrammingSynopsis


2/43


3/43

Features of OOPs language

1. Emphasis on data rather than

procedure.2. Program divided into objects (class).

3. Data is hidden and can not beaccessed by external functions.

4. Follows bottom-Up approach.


4/43

An object oriented programmingmethod has many advantages,

some of them are flexibility andcode reusability.

All the programming languagessupporting Object oriented

Programming will be supportingthese three main concepts:


5/43

About Object Oriented LanguagesAccording to Bjarne Stroustrup, author of the C++

programming language, for a language to callitself object-oriented, it must support threeconcepts: objects, classes, and inheritance.

1. Fully Object Oriented Language:-.Net,Java.

2. Partially Object Oriented Language:-C++

3. Object based Language:- Vb6.0


6/43

Class and ObjectsWe can think of a class as simply a type (just

like char, int, or long) that has methodsassociated with it .

Object is an instance of a type or class.

A class is a blueprint for a given set offunctionality, and an object created

based on a particular class has all thefunctionality of the class built right in.Instances of classes are called as Objects. They might

represent individual employees if Employee is defined asa Class..


7/43

Three Pillars of OOPs Encapsulation

Inheritance

Polymorphism


8/43

EncapsulationEncapsulation is process of keeping data

and methods together inside objects.

encapsulation is realized through the

classes. A Class can contain data andmethods.

Lke Employee class will provide properties(Name,Age ....) as well as actions(Calculatesalary, GoonLeave....) of theemployee entity.

Instances of classes are called as Objects. They mightrepresent individual employees.


9/43


10/43

Function OverloadingFunction overloadingallows the existence of

multiple functions with the same name,

differing only in the parameters.

For example, if you were creating a method to printa data, you might declare several functions, eachnamed Write.

One version would accept a string as a parameter;another, an integer; and yet another, a

DateTime,object.But Overloading allows to define many functionhaving different parameters but still the samename.


11/43

class Salary

{

int basic, comm, deduct, ta, ha =0;

public void getnetsal(int b,int c,int d)

{

Console.WriteLine(b+c-d);

}

public void getnetsal(int b, int c, int d,int t,int h)

{

Console.WriteLine(b + c + t + h - d);

}

}


12/43

PropertiesProperties are such members of classes,

structs or interfaces that provide a flexiblemechanism to read, write, or compute the

values of private fields through accessors.

Unlike fields, properties do not designate storagelocations. Instead, properties have accessorsthat read, write, or compute their values.

[modifiers] type identifier{accessor-declaration}


13/43

Class transaction { string acc_id; int dipos,withd,bal; private string acc_no //read and write

{ set { acc_id=value; }

get { return(acc_id); } }

private int balance //read only {

get { return(bal); }

}

private int withdraw //write only { set { withd=value; bal-=withd; }

}

}


14/43

Constructor and DestructorConstructor is special function that is called automatically

whenever new instance is created.

It is used to initialize the values for class data member.

There can be any number of constructors in a program butmust be differ in terms of their parameters, Called asOverloaded constructor.

Destructor is such special function that is invokedautomatically when an instance is destroyed.

Note :- The name of Constructor and Destructor must be the samename as Class name where both never return any value.

Constructor can take one or more parameters but destructor can not.

Destructor starts with (~) titles character.


15/43

Account() //Default { }

Account(int ac_no,string nm,) //Overloaded { }

Account(int ac_no,string nm,int bal) //Overloaded { }

~Account() //Destructor { }


16/43

ObjectsObject is an instance of a type or

class.

Instances of classes are called as Objects.

For example there might be three instances of theEmployee - Ram , Raj and Tom.

They might represent individual employees.


17/43

Employees Ram=new Employee();

Or Employee Raj;

Raj=new Employee(); Or Customer abc=new

customer(101,hyd); //CallingOverloaded constructor


18/43

InheritanceInheritance relates to the programmer's ability to

specify that one class has a kind-of relationshipwith another class. Through inheritance, you cancreate (or derive) a new class that's based on an

existing class.In a few words, Inheritance is the process of

creation new classes from already existingclasses.

inheritance feature allows us to reuse some parts ofcode .

The .NET framework has many baseclasses. Everything is derived fromSystem.Object .


19/43

Class class1 {.}Class class2 : class1 {.}

class class1

{

public int i; }

class class2 : class1 { private void f1()

{ i = 10; } }


20/43

Types OfInheritance1. Singe Level or Single Inheritance

2. Multilevel Inheritance

3. Multiple Inheritance4. Hierarchical Inheritance

5. Hybrid Inheritance


21/43

Base Class

Child Class

Single Level Multi level

Base Class

Child Class

Grand Child

Multiple

Class1

Class12

Class2


22/43

.

Hybrid

Base Class

Child1 Child2

Child11

Base Class

Child1 Child2

Child12

Hierarchical

Multiple

Multiple Inheritance is not supported by in .Net.

Hierarchical


23/43

Multiple inheritanceMultiple inheritance is the possibility that a child

class can have multiple parents. Human beingshave always two parents, so a child will havecharacteristics from both parents.

In OOP, multiple inheritance might become difficultto handle because it allows ambiguity for thecompiler. There are programming languagessuch as C++ that allow multiple inheritance;however, other programming languages such asJava and the .NET Framework languages do not

allow multiple inheritance. Multiple inheritancecan be emulated in .NET using Multiple InterfaceInheritance .


24/43

Access Modifiersprivate Access limited to the containing type.

protectedAccess limited to the containing class or types

derived from the containing class.

internal Access limited to this program.

Protected internal Access limited to this program or

types derived from the containing class outside theprogram.

public Access not limited.

***Bydefault All members(data & function) will be Private.


25/43

Sealed classSome object model designs need to allow the

creation of new instances but not inheritance, ifthis is the case, the class should be declared assealed.

A sealed class is a class that does not allowinheritance.

To create a sealed class in C# :-

sealed class Shape

To create a sealed class in VB.NET, :

NonInheritable Class Shape


26/43

AbstractionAbstraction is "the process of identifying common

patterns that have systematic variations; anabstraction represents the common pattern andprovides a means for specifying which variation

to use" .Great example is a bank account. People own

savings accounts, checking accounts, creditaccounts, investment accounts, but not genericbank accounts.

In this case, a bank account can be an abstract

class and all the other specialized bank accountsinherit from bank account.


27/43

An abstract class is a parent class thatallows inheritance but can never be

instantiated.Abstract classes contain one or more

abstract methods that do not haveimplementation. Abstract classes

allow specialization of inheritedclasses.


28/43

To create an abstract class in C# :-

abstract class Shape

To create an abstract class in VB.NET,

MustInherit Class Shape


29/43

abstract class Vehicle { public float weight; public byte tyre;

public abstract string start(); //abstract function

public void stop() //unabstract function { Console.WriteLine("Vehicle Stoped"); }

}

Note :- An abstract class can have zero or more abstract as well asunabstract function.

But an abstract function can only be declared inside Abstarct class. But abstract function does not have body part but only declration. The abstarct function must be public.


30/43

class car :Vehicle

{

public override string start()

{

return("started");

}

Note :- If a child class inherits from a abstract class , thechild class has to define the body of all abstract functionexisting into base class using override keyword.


31/43

Virtual keywordA virtual property or method has an implementation in the

base class, and can be overriden in the derived classes.The virtual keyword allows polymorphism too.

To create a virtual member in C#:-

public virtual void Draw() {-------} --Base class MemberPublic override void Draw(){-----} Child class

To create a virtual member in VB.NET :-

Public Overridable Function Draw()


32/43

class clas3 { public virtual void vf() { } Public void f1()

{ } }

class cls4 : clas3 { public override void vf() { }

Public void new f1() { } }


33/43

Override keywordOverriding is the action of modifying or

replacing the implementation of theparent class with a new one.

Parent classes with virtualvirtual oror abstractabstractmembers (in Abstract class) allowderived classes to override them.

To override a member in C# :-

public override void CalculateArea() To override a member in VB.NET :-Public Overrides Function CalculateArea()


34/43


35/43

interface Iface

{

void send(string msg); string get();

}

Note :-Interface Members are by default Public.A field can not be defined within an Interface.


36/43

class Msg : Iface { string message; public void send(string msg) {

message=msg; }

public string get() { return(message);

} }Note :- A class can Implement any number ofInterfaces.

class Msg : Iface,Iface2 { ------- }The class has to implement all of the members declared into Iface and Iface2.


37/43

Avoiding Name Ambiguity

interface Interdemo{ void Show();}interface Interdemo1{ void Show();}

class Interclash:Interdemo,Interdemo1{ void Interdemo.Show() {

Console.WriteLine("Show() method Implemented"); }void Interdemo1.Show() {

Console.WriteLine("Display() method Implemented"); }

To call the members :-

Interclash inter = new Interclash();inter.Interdemo.Show();

inter.Interdemo1.Show(); }


38/43

Why Use Interfaces?

To allow a class to inherit multiplebehaviors from multiple interfaces.

To avoid name ambiguity between the

methods of the different classes aswas in the use of multiple inheritancein C++.

To combine two or more interfaces

such that a class need only implementthe combined result.


39/43

Note constructor also inherits base class constructor. To override already defined method (into base class ) into child class a

keyword new is used. A virtual function can have body in base class but a abstract function

can never have body in base class. A virtual function can reside in abstract class as well as unabstract

class also. A abstract function can only be appear in abstract class. A abstract class can have abstract as well as unabstract function also. A virtual and abstract both type of function can be overidden in child

class using override keyword.

An Object can not be created for Abstract classes or Interfaces.

Interface can not contain any field (variable).

An abstract can contain field and unabstract functions also butInterface can contain only abstract functions.

An Interface can be defined within a class also.


40/43

Operator OverloadingOperator is used to defined, what function need to perform with the

Operands.

Like res= num1 + 100;

The Operator Overloading is a way to redefine the functionalityOf an existing Operator.

This gives the operator more than one meaning, or "overloads" it. Thecompiler distinguishes between the different meanings of anoperator by examining the types of its operands.

You can redefine the function of most built-in operators globally or ona class-by-class basis. Overloaded operators are implemented asfunctions.


41/43

Example class op_cls { int num1;

public op_cls() { num1=0; }

public op_cls(int arg) { num1=arg; }

public static op_cls operator +(op_cls obj1,op_cls obj2) { op_cls obj3=new op_cls();

obj3.num1=obj1.num1+obj2.num1;

return(obj3); }

public void show() { Console.WriteLine(num1.ToString()); }

}


42/43

Using Overloaded Operator op_cls o1=new op_cls(100);

op_cls o2=new 0p_cls(200);

op_cls o3=new op_cls();

o3=o1+o2;

o3.show(); //300


43/43

Overloadable Operators

+, -, !, ~, ++, --,true, false

+, -, *,/, %, &, |, ^,

=, ., ?:, ->, new, is,sizeof, typeof

These unaryoperators can beoverloaded.

These binaryoperators can beoverloaded.

These operators

cannot beoverloaded.

oops csharp

Documents