Total oop in c# dot net

PROPAGATING IN .NET
By Muhammad Naveed
MCS University of AJK, DIT
Instructor Moon Creations School of IT
1

OOP
 Function +data
 In modular programming functions and data is
separated.
 i.e.
student
{
Student info
}
Courses
{
Course info.
}
210/13/2012Muhammad Naveed

OOP
 So every thing is separated data and
operations .
 Class is an instance of an object, which
defines state and behavior of an object.
 Object can interacts with each other by
message passing.

Class
 To house (among other things)
 In class we provide one or more methods that are
designed to perform the class tasks.
 For example: a bank account class might contain one or
more methods to deposit money, withdraw money and
balance inquiry.
 Collection of similar objects, with different names
 Class in an passive entity.
 Class in template or blue print
 Class is module or sketch.
 Class has data members and functions on which class
performs its functionalities.
 Data and functions are combined

Object
 We have to build a object of class to actually
gets its fruits. C# called OOP
 Object is an active entity.
 Object has properties or methods/
attitudes/ functions/operations/data
members/fields
 So objects has state and behaviors
 Students is an object.
 Employee is an object

Methods
 Performing a task in an application requires
a method. The method describes the
mechanism that actually perform its task.
The method hides from its user the complex
tasks. Just as the accelerator pedal of a car
hides from the driver the complex
mechanism of making the car go faster.

Attributes
 Every objects muse have some attributes or properties
like color, size, shape etc.
 Attributes are specified by the class’ instance variables
 Properties Get assessors and set assessors
 Attributes are not necessarily accessible directly. The car
manufacturer does not want drivers to take apart the
car’s engine to observe the amount of gas in its tank.
 Instead the driver can check the fuel gauge on the
dashboard.
 So in c# we use get accessors for reading and set
accessors for storing values.

STATIC Methods
 Sometimes a method performs a task that
does not depend on the contents of any
object. So can be called with out creating its
object this is called static method.
 Syntax
 ClassName. MethodName(arguments)
 Always called with class name and method
name

Constructor
 Constructor is used to initialize the object of
the class.
 Behaves like Function
 Constructor is just like function, but it is a
special type of function.
 Same name like class
 Class student
 Public student( )
 Defaults constructor has no argument or
parameters

Properties Function
 These are get and set functions
 Not a fully function but behaves like
function.
 Used to get and set values of private data
members of a class

 int n;
 Console.WriteLine("Enter a number");
 n = Convert.ToInt32(Console.ReadLine());
 if (n > 0)
 {
 Console.WriteLine("The Number is +ve");
 }
 else
 {
 Console.WriteLine("The number is -ve");
 }
 Console.Read();
 int n;
 n = 1;
 while (n <= 5)
 {
 Console.WriteLine("Kashmir");
 n++;
 }
 Console.Read();

Major Concepts
 OOP
 Classes
 Objects
 Methods
 Properties
 Instance Variables

Features of OOP
 Inheritance
 Polymorphism
 Encapsulation
 Abstraction

STRUCTURED VS. OO PROGRAMMING
17
STRUCTURED PROGRAMMING:

Structured Programming
 Using function
 Function & program is divided into modules
 Every module has its own data and function
which can be called by other modules.

OBJECT ORIENTED PROGRAMMING

OBJECT ORIENTED PROGRAMMING
Objects have both data and methods
Objects of the same class have the same data elements
and methods
Objects send and receive messages to invoke actions
Key idea in object-oriented:
The real world can be accurately described as a collection of
objects that interact.

Basic terminology
object
- usually a person, place or thing (a noun)
method
- an action performed by an object (a verb)
attribute
- description of objects in a class
class
- a category of similar objects (such as automobiles)
- does not hold any values of the object’s attributes

Example for attributes and methods
Attributes:
 manufacturer’s name
 model name
 year made
 color
 number of doors
 size of engine
 etc.
Methods:
 Define data items
(specify
manufacturer’s name,
model, year, etc.)
 Change a data item
(color, engine, etc.)
 Display data items
 Calculate cost
 etc.

WHY OOP?
Save development time (and cost) by reusing code
once an object class is created it can be used in other
applications
Easier debugging
classes can be tested independently
reused objects have already been tested

DESIGN PRINCIPLES OF OOP
Four main design principles of Object-Oriented
Programming(OOP):
Encapsulation(information hiding)
Abstraction(hide unnecessary details )
Polymorphism(same thing behave differently)
Inheritance(derived class inherit from base class)

ENCAPSULATION
Also known as data hiding
Only object’s methods can modify information in the
object.
Data and Function Encapsulated within a single
package ‘class’.
Analogy:
ATM machine can only update accounts of one
person or object only.

Abstraction
 Focus only on the important facts about the
problem at hand
 to design, produce, and describe so that it can be
easily used without knowing the details of how it
works.
Analogy:
 When you drive a car, you don’t have to know how
the gasoline and air are mixed and ignited.
 Instead you only have to know how to use the
controls.
 Draw map

POLYMORPHISM
the same word or phrase can mean different things
in different contexts
Analogy:
In English, bank can mean side of a river or a place
to put money
move -

Function Overloading
 The operation of one function depends on the
argument passed to it.
 Example: Fly(), Fly(low), Fly(150)

INHERITANCE
Inheritance—a way of organizing classes
Term comes from inheritance of traits like eye color,
hair color, and so on.
Classes with properties in common can be grouped so
that their common properties are only defined once.
Superclass – inherit its attributes & methods to the
subclass(es).
Subclass – can inherit all its superclass attributes &
methods besides having its own unique attributes &
methods.

AN INHERITANCE HIERARCHY
30
Vehicle
Automobile Motorcycle Bus
Sedan Sports Car School BusLuxury Bus
What properties does each vehicle inherit from the types
of vehicles above it in the diagram?
Superclass
Subclasses

OBJECT-ORIENTED PROGRAMMING
LANGUAGES
 Pure OO Languages
C#, Smalltalk, Eiffel, Actor, Java
 Hybrid OO Languages
C++, Objective-C, Object-Pascal

Review: Introduction to Object
Orientation
 What are the four basic principles of object
orientation? Provide a brief description of
each.
 What is an Object and what is a Class? What is
the difference between them?
 What is an Attribute?
 What is an Operation?
 What is inheritance?
 What is polymorphism?
 Describe the strengths of object orientation.

Review: Introduction to Object
Orientation
 State 2 differences between functional
programming and OOP.
 What are the four basic principles of object
orientation? Provide a brief description of
each.
 What is an Object and what is a Class? What is
the difference between them?
 What is an Attribute?
 What is an Operation?
 Describe the strengths of object orientation.

Polymorphism
 Compile time polymorphism(Overloading)
 Run time Polymorphism( Overriding )

Compile Time
Polymorphism(Overloading)
 Can be Achieved by
 Function Overloading
 Operator Overloading
 Constructor Overloading

Compile Time
 It means same thing behaves differently
 Public void get()
 Public void get(int r)
 Public void get(int r, string n)
 Public void get(int r, string n, string rem….)
 So same function behaves differently by increasing
number of parameters or arguments i.e. no argument, one
argument or two or may be three or even more.
 So this is how we can achieve Compile time polymorphism
that is overloading
 Also function type or signature can be changed, so that
it can be define with same name but with different
parameters.

Example

Compile Time
 Some operators can also behaves differently
called operator overloading (polymorphism).
Operator can be redefined to achieve the
operator overloading.

Operator Overloading

Example 2

Compile Time
 3. Constructor Overloading

Lecture
 Intro to GUI using C#
 Windows Applications
 Windows Forms

Run Time Polymorphism
(Overriding)
 We have learned about compile time
polymorphism which is overloading.
 Public void get(int n)
 Public static room operaotr +(room rm1, room
rm2)
 Constructor Overloading
 Public student(string n,…)

(Overriding)
 Now in this case we have to change the
signature or nos of parameters to get
function overloading. Which we have done.
 But in some situations, we have to use same
function with the same name signature this
is called overriding. this situation can be
used in parent class relationship i.e.
 Where we have to use virtual function, That
needs to be redefined again and again. It
gives the 1st definition of that function,

(Overriding)
 Because same name with same signature
needs to be redefined using virtual keyword
in the parent class.
 And to access this in the child class we have
to use override keyword.

Example

OOP: Inheritance
 Inheritance a form of software reuse.
 Lets you save much of your time in software
development.
 The existing class from which a new class
inherits is called base class, and the new
class is called derived class
 Each derived class can become the base
class for next extended class
 And new data members can be added.
10/13/2012Muhammad Naveed 55

OOP: Inheritance
Base Class Derived Class
Student Graduate Student, Undergradulate
Shape Oval, Rectangle, elpse
Loan CarLoan, HomeLoan
BankAccount Currant, Saving etc

OOP: Inheritance
Community
Member
Employee
Faculty
Admin Teacher
Staff
Student Alumnus

OOP: Inheritance
 Protected Members
 Commonly we used Public and Private
 Public data members are accessible
whenever the application has a reference to
an object of that class or one of its derived
class.
 Private data members are inherited from its
derived class, but are not accessible by
derived class and methods.

OOP: Inheritance
 Protected :
 Provides an intermediate level of
accessibility b/w public and private. These
can be accessible by members of that base
class and by members of its derived class

Relationship b/w base
classes and derived classes

 The above examples show polymorphism,
inheritance, constructor overloading and
function overloading, private and public
data members w.r.t access.
 Reference Book
 C# 2010 for programmers.
 Chapter 11, OOP Programming: inheritance
page:320 etc
summery

Abstract Class and Methods
 We can not create object of the Abstract
Class.
 The purpose of the abstract class is
primarily to provide and appropriate base
class from which other classes can inherit
and thus share a common design.
 Public abstract void show()//abstract
method

Case Study
 Scenario

Payroll System Using
Polymorphism
 A company pay in employees on a weekly basis.
 The employees are of four types.
 Salaried Employees: are paid a fixed weekly salary
regardless of the number of hours worked.
 Hourly Employees: are paid by hour and receive
“time and a half” overtime pay for their sales.
 Salaried commission employees: are paid a
percentage of their sales.
 For the current pay period the company has decides
to reward salaried commission employees by adding
10% to their base salaries.
 Company demands a C# application.

Solution
 We use abstract class as employee for
general concept.
 The other class that extends from employee
abstract class are: SalariedEmployee,
CommissionEmployee and
HourlyEmployee.
 ClassBasePlusCommissioEmployee Which
extends from CommissionEmployee.
 UML

Employee
SalariedEmployee CommissionEmployee
BasePlusCommissionEmployee
HourlyEmployee

Cases
Classes Earnigns ToString
Employee Abstract The abstract class for all
other classes as a
foundation first
name,last name, social
security number SSN
Salaried Employee weeklySalary Salaried
employee:employee
Weekly salary:
Hourly Employee If hours<=40
Wage=hours
Ifhours>40
40*wage+(hours-
40)+wage=1.5
Hourlty
employee:employee
Houtly wage :wage
Hours work:hours
Comission Employee commissionRate*grossS
ales
Inherit from employee
Gross sale:grassSales
Comission
rate:comissionRate
BasePlusComissionEmpl
oyee
comissionRate*grossSal
es+baseSalry
Base Salaried comsiion
employee:10/13/2012Muhammad Naveed 72

Solution Book page no344

Exception Handling
 Try
 {
 Throuth exception()
 }
 Catch
 {
 Catch exception()
 }
 Finally
 {
 Show final()
 }

Overview

GUI : Windows Forms

Events And Handling them

Total oop in c# dot net

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