Inheritance

InheritanceBhushan Mulmule

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object

Account

SavingAccount

CurrentAccount

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Part I◦ Inheritance: When, Why, How◦ Inheritance in .NET Framework◦ Inheritance Demo Example

Part II◦ Constructor Flow in Inheritance

Part III◦ Access Modifiers: private, public, protected, internal, protected internal

Agenda


ImplementationInheritanceInterface

ImplimentationImplementation

InheritanceInterface

Implementation


class MyBase{ private int field1; public void fun1() { }}

class MyDerived : MyBase{ private int field2; public void fun2() { }}

Inheritance enables you to create new classes that reuse, extend, and modify the behavior that is defined in other

classes.

Base class

Derived class

field1 field2obj

Object of MyDerived


When to use inheritance?


OnRollEmployee

EmpNo

Name

Department

Designation

BasicSalary

HRA

GrossSalary

PF

NetSalary

OffRollEmployee

EmpNo

Name

Department

Designation

PerHourRate

WorkedHours

NetSalary


Employee

EmpNo

Name

Department

Designation

NetSalary

OnRollEmployee

BasicSalary

HRA

GrossSalary

PF

OffRollEmployee

PerHourRate

WorkedHours

Generalized Base Class

Specialized Derived Class


object

StackHolder

Client Customer

Supplier

object

Account

SavingAccount

CurrentAccount

Few more examples…


Inheritance in .NET Framework


inheritance hierarchy represents an "is-a" relationship and not

a "has-a" relationship.

can reuse code from the base classes.

need to apply the same class and methods to different data

types.

The class hierarchy is reasonably shallow, and other

developers are not likely to add many more levels.

want to make global changes to derived classes by

changing a base class.

Inheritance is a good choice when


Every class directly of indirectly derives from

object class

Multiple class Inheritance is not allowed.

Multilevel is obvious!

Multiple interface implementation is possible.

Important


Part I◦ Inheritance: When, Why, How◦ Shadowing◦ Inheritance Demo Example



Agenda


Constructor never get derived Always base class constructor executes

first.


class MyBase{ protected int no1, no2;

public MyBase() { }

public MyBase(int n1,int n2) { this.no1 = n1; this.no2 = n2; }}

class MyDerived : MyBase{ private int no3;

public MyDerived() : base() { }

public MyDerived(int n1,int n2,int n3)

: base(n1,n2) { this.no3 = n3; }}

MyDerived obj1 = new MyDerived();

MyDerived obj2 = new MyDerived(10, 20, 30);

no1 no2 no3

Client Code

Part I◦ Inheritance: When, Why, How◦ Shadowing◦ Inheritance Demo Example



Agenda


Access modifiers are keywords used to specify the declared accessibility of a member or a type

•Access is not restricted.public

•Access is limited to the containing type.private

•Access is limited to the containing class or types derived from the containing class.protected

•Access is limited to the current assembly.internal

•Access is limited to the current assembly or types derived from the containing class.protected internal


class A{ private int no1; protected int no2; internal int no3; protected internal int no4; public int no5;} class B : A{}

class C{}

class D : A{}

class E{}

Assembly - 1 Assembly - 2

•Ano1

•A, B, Dno2

•A, B, Cno3

•A, B, C, Dno4

•A, B, C, D, Eno5

What is accessible where?


Bhushan [email protected]




Inheritance

Technology

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