c# and .net VTU

8/11/2019 c# and .net VTU

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Subject Name: C# AND .NET CONCEPTS

Subject Code: 10CS761

Prepared By: ! Su"at$% S & A!!t. Pro'e!!or() Dr*o+e!$ &Pro'e!!or(

Departmet: CSE

Date : ,,.0-.,01

10//1 1C#AND .NET 10CS7612N3T 34


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UNIT IV

OBJECT ORIENTED

PROGRAMMING WITH

C#

10//1 ,C#AND .NET 10CS7612N3T 34


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10//1

DEFINITION OF C# CLASS

C#AND .NET 10CS7612N3T 34

Its a buildin! bloc$ that contains properties and functionalities that describe

so&e !roup of ob(ectsCreatin! ob(ect of a specific class type called instance of the classIs a )ser Defined Type*)DT+ that is co&posed of data and functions that act

upon this data,ccess specifiers specify the access rules for the &e&bers as %ell as the class

itself- if not &entioned then the default access specifier for a class type

is internal. Default access for the &e&bers is ri!ateData type specifies the type of variable- and return type specifies the data

type of the data- the &ethod returns- if anyTo access the class &e&bers- you %ill use the dot *.+ operatorThe dot operator lin$s the na&e of an ob(ect %ith the na&e of a &e&ber


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10//1 C#AND .NET 10CS7612N3T 34

S"NTA

/access specifier0 class class1na&e

2

33 &e&ber variables

/access specifier0 /data type0 variable45

/access specifier0 /data type0 variable65

... /access specifier0 /data type0 variable75

33 &e&ber &ethods

/access specifier0 /return type0 &ethod4*para&eter1list+

2 33 &ethod body 8

/access specifier0 /return type0 &ethod6*para&eter1list+2 33 &ethod body 8

...

/access specifier0 /return type0 &ethod7*para&eter1list+

2 33 &ethod body 88


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10//1

EAMPLEusin! Syste&5

na&espace 'o9,pplication

2

class 'o9

2

public double len!th5 33 en!th of a bo9

public double breadth5 33 'readth of a bo9

public double hei!ht5 33 ;ei!ht of a bo9

8

class 'o9tester 2

static void ar!s+

2

'o9 'o94 ? ne% 'o9*+5

33 Declare 'o94 of type 'o9

'o9 'o96 ? ne% 'o9*+5

33 Declare 'o96 of type 'o9

double volu&e ? @.@5

33 Store the volu&e of a bo9 here

33 bo9 4 specification

'o94.hei!ht ? A.@5

'o94.len!th ? B.@5

'o94.breadth ? .@5

6C#AND .NET 10CS7612N3T 34


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10//1

EAMPLE$C%nt&'(()


33 bo9 6 specification

'o96.hei!ht ? 4@.@5

'o96.len!th ? 46.@5

'o96.breadth ? 4.@5

33 volu&e of bo9 4

volu&e ? 'o94.hei!ht 'o94.len!th 'o94.breadth5

Console.Friteine*GHolu&e of 'o94 : 2@8G- volu&e+5

33 volu&e of bo9 6

volu&e ? 'o96.hei!ht 'o96.len!th 'o96.breadth5 Console.Friteine*GHolu&e of 'o96 : 2@8G- volu&e+5

Console."eadey*+5

8

8

8


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10//1

CONSTRUCTORS IN C#

, class +%n,tr-+t%ris a special &e&ber function of a class that is e9ecuted%henever %e create ne% ob(ects of that class

, constructor %ill have e9act sa&e na&e as the class and it does not have

any return type

, &e.a-lt +%n,tr-+t%rdoes not have any para&eter but if you need a

constructor can have para&eters. Such constructors are

called ara/eteri0e& +%n,tr-+t%r,. This techniJue helps you to assi!n

initial value to an ob(ect at the ti&e of its creation



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10//1

EAMPLEusin! Syste&5

na&espace ine,pplication

2 class ine

2 private double len!th5

33 en!th of a line

public ine*+

2Console.Friteine*GOb(ectis bein! createdG+5

8

public void seten!th* double len +

2 len!th ? len5 8

public double !eten!th*+

2

return len!th5 8

static void ar!s+ -C#AND .NET 10CS7612N3T 34


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10//1

DESTRUCTORS

, &e,tr-+t%ris a special &e&ber function of a class that is e9ecuted%henever an ob(ect of its class !oes out of scope

, &e,tr-+t%r%ill have e9act sa&e na&e as the class prefi9ed %ith a tilde *K+

and it can neither return a value nor can it ta$e any para&eters

Destructor can be very useful for releasin! resources before co&in! out of

the pro!ra& li$e closin! files- releasin! &e&ories etc Destructors cannot be inherited or overloaded



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10//1

EAMPLEusin! Syste&5

na&espace ine,pplication 2

class ine 2 private double len!th5

33 en!th of a line

public ine*+ 33 constructor

2 Console.Friteine*GOb(ect is bein! createdG+5 8

Kine*+ 33destructor

2 Console.Friteine*GOb(ect is bein! deletedG+5

8 public void seten!th* double len +

2 len!th ? len5 8

public double !eten!th*+

2 return len!th5 8

static void ar!s+?



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Public Interface is any ite& declared in a class usin! public$ey%ord

Class &e&bers %hich are accessible fro& an ob(ect variable are

called as public interface of a class

Public interface of a class is populated by

4.&ethods&e&ber functions

6.properties ,ccessors and &utators

.public fields or public variables

1,C#AND .NET 10CS7612N3T 34

PUBLIC INTERFACE


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10//1

PILLARS OF OOP

Encapsulation

Inheritance

Poly&orphis&



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ENCAPSULATION

Procedure of coverin! up of data and functions into a sin!le unit*called class+

,n encapsulated ob(ect is often called an abstract data type

NEED FOR ENCAPSULATION

Encapsulation provides a %ay to protect data fro& accidental

corruption. "ather than definin! the data in the for& of public- %e

can declare those fields as private. The Private data are &anipulated

indirectly by t%o %ays:

The first &ethod is usin! a pair of conventional accessor and

&utator &ethods

,nother one &ethod is usin! a na&ed property



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ENCAPSULATION USING ACCESSORS AND

MUTATORS To &anipulate the data in that class *Strin! departna&e+ %e define an

accessor *!et &ethod+ and &utator *set &ethod+

usin! syste&5public class Depart&ent2

private strin! departna&e5.......33 ,ccessor.

public strin! LetDepartna&e*+2return departna&e5833


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10//1

;ere %e use t%o separate &ethods to assi!n and !et the reJuired

data

public static int ar!s+

2

Depart&ent d ? ne% Depart&ent*+5

d.SetDepartna&e*GEECT"O7ICSG+5

Console.Friteine*GThe Depart&ent is :GMd.LetDepartna&e*++5

return @5

8

In the above e9a&ple %e canNt access the private data departna&e

fro& an ob(ect instance. Fe &anipulate the data only usin! those

t%o &ethods



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10//1

ENCAPSULATION USING PROPERTIES usin! syste&5

public class Depart&ent2

private strin! departna&e5

public strin! Departna&e

2

!et

2

return departna&e5

8set

2

departna&e?value5

8

8

8

public class Depart&ent&ain

2public static int ar!s+

2

Depart&ent d? ne% Depart&ent*+5

d.departna&e?GCo&&unicationG5

Console.Friteine*GThe Depart&ent is 2@8G- d.Departna&e+5

return @5

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10//1

The property has t%o accessor !et and set. The !et accessor returns the

value of the so&e property field.

The set accessor sets the value of the so&e property field %ith the

contents of GvalueG. Properties can be &ade readonly.

This is acco&plished by havin! only a !et accessor in the property

i&ple&entation.



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The class "eadDepart&ent has a Departna&e property that

only i&ple&ents a !et accessor.

It leaves out the set accessor. This particular class has a

constructor- %hich accepts a strin! para&eter.

The


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10//1

WRITE ONL" PROPERT"

Properties can be &ade also Friteonly. This is acco&plished by havin! onlya set accessor in the property i&ple&entation.

usin! syste&5

public class FriteDepart&ent

2

private strin! departna&e5public strin! Departna&e

2

set

2

departna&e?value5

Console.Friteine*GThe Depart&ent is :2@8G-departna&e+5

8

8

8

public class FriteDepart&ain

2 ,1C#AND .NET 10CS7612N3T 34


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10//1

The class FriteDepart&ent has no% has a Departna&e

property that only i&ple&ents a set accessor. It leaves out the !et accessor.

The set accessor &ethod is varied a little by it prints the value

of the departna&e after it is assi!ned.

,,C#AND .NET 10CS7612N3T 34


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10//1

INHERITANCE

"euse e9istin! code

"elationship bet%een 6 or &ore classes

,ll variables and &ethods in the base class can be called in the

derived classes. 6 flavors of inheritance

4. classical inheritance*isa relationship+

6.contain&ent3dele!ation &odel*hasa relationship+

,5C#AND .NET 10CS7612N3T 34


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10//1

CLASSICAL INHERITANCE

7e% classes &ay e9tend the functionality of other classes

Isa relationship

Sales person isa E&ployee

,C#AND .NET 10CS7612N3T 34


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10//1

;ere base classes are used to define !eneral characteristics that are co&&on to all

subclasses

)sin! Syste&5

public class parentclass

2

public parentclass*+

2

Console.Friteine*parent constructor+58

public void print*+

2

Console.Friteine*I& a parent class+5

8

8

public class childclass:parentclass

2

,C#AND .NET 10CS7612N3T 34


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10//1

C%ntain/ent1Dele2ati%n /%&el

;asa relationship

Specifies ho% one class is &ade up of other classes*the parts+

public class en!ine

2

public void start*+

2

Syste&.console.Friteine* En!ine started+5

88

public class car

2

public strin! &a$e5

public en!ine e5,6C#AND .NET 10CS7612N3T 34


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BASE 3E"WORD

)sed to access the &e&bers of base class fro& %ithin a derived class

4.Call a &ethod on the base class that has been overridden by another &ethod

6. Specifies %hich base class constructor should be called %hen creatin!

instances of the derived class

,7C#AND .NET 10CS7612N3T 34


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10//1

)sin! Syste&5

Class ,

2

Public int i5

Public a*int i+

2

This.i?i58

8

Class ':,

2 7e% int i?@5

Public '*int i+:base*i+2 This.i?4@@5

8

Public void display*+

2 Console.Friteine*value of base class 4 is 2@8-base-i+5

Console.Friteine*value of derived class 4 is 2@8-i+5

8 ,C#AND .NET 10CS7612N3T 34


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10//1

PREVENTING INHERITANCE* SEALED CLASS

Fhen a class is declared %ith sealed $ey%ord- it cannot be inherited

Error %ill occur if a sealed class is declared as base class of another

class

It is used to prevent the derivation of a class

Structs are i&plicitly sealed.

,-C#AND .NET 10CS7612N3T 34


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10//1

SEALED METHODS

, &ethod cant be declared as sealed

Fhen overridin! a &ethod in a derived class- the override &ethod

can be declared as sealed.

Fe can avoid further overridin! of the &ethod %hich is declared assealed.



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10//1

EAMPLE

)sin! Syste&5

Sealed class ,

2 public void display*+

2

Console.Friteine*virtual &ethod+58

8

public class ':,

2

public override sealed void display*+

2

Console.Friteine*sealed &ethod+5

8 51C#AND .NET 10CS7612N3T 34


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10//1

PROTECTED 3E"WORD

The r%te+te&$ey%ord is a &e&ber access &odifier. , protected &e&ber is

accessible %ithin its class and by derived class instances. or a co&parisonof r%te+te&%ith the other access &odifiers

, protected &e&ber of a base class is accessible in a derived class only if the

access occurs throu!h the derived class type

class ,

2 protected int 9 ? 465 8

class ' : ,

2 static void


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10//1

PROTECTED 3E"WORD$CONTD(()

The state&ent a.9 ? 4@ !enerates an error because it is &ade %ithin the static

&ethod


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10//1

POL"MORPHISM

P%l4/%r5i,/&eans havin! &any for&s one interface- &ultiple functions

Poly&orphis& can be static or dyna&ic

In ,tati+ %l4/%r5i,/ the response to a function is deter&ined at the

co&pile ti&e

In &4na/i+ %l4/%r5i,/ - it is decided at runti&e



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10//1

D"NAMIC POL"MORPHISM usin! Syste&5

public class Dra%in!Ob(ect

2 public virtual void Dra%*+ 2 Console.Friteine*GIN& (ust a !eneric dra%in! ob(ect.G+5 88

public class ine : Dra%in!Ob(ect

2 public override void Dra%*+

2 Console.Friteine*GIN& a ine.G+5 88

public class Circle : Dra%in!Ob(ect


2 Console.Friteine*GIN& a Circle.G+5 88

public class SJuare : Dra%in!Ob(ect


2 Console.Friteine*GIN& a SJuare.G+5 88 usin! Syste&5public class Dra%De&o

2 public static int dOb( ? ne% Dra%in!Ob(ect=>5

dOb(=@> ? ne% ine*+5

dOb(=4> ? ne% Circle*+5

dOb(=6> ? ne% SJuare*+5

dOb(=> ? ne% Dra%in!Ob(ect*+5

foreach *Dra%in!Ob(ect dra%Ob( in dOb(+

2 dra%Ob(.Dra%*+5 8

return @5 88

OUTPUT*

IN& a ine.

IN& a Circle.

IN& a SJuare.

IN& (ust a !eneric dra%in! ob(ect.



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10//1

STATIC POL"MORPHISM

sa&e function rint$)is bein! used to print different data types

usin! Syste&5na&espace Poly&orphis&,pplication

2 class Printdata

2 void print*int i+

2 Console.Friteine*GPrintin! int: 2@8G- i +5 8

void print*double f+

2 Console.Friteine*GPrintin! float: 2@8G - f+5 8void print*strin! s+

2 Console.Friteine*GPrintin! strin!: 2@8G- s+5 8

static void ar!s+

2 Printdata p ? ne% Printdata*+5 33 Call print to print inte!er p.print*A+5

33 Call print to print float p.print*A@@.6B+5

33 Call print to print strin! p.print*G;ello CMMG+5 Console."eadey*+5 888

OUTPUT*

Printin! int: A

Printin! float: A@@.6B

Printin! strin!: ;ello CMM



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10//1

ABSTRACT METHODS AND CLASSES


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10//1

EAMPLE

public abstract class shape

2

public abstract void dra%*+5

8

,bstract &ethods have no i&ple&entation Derived classes of the abstract class &ust i&ple&ent all the abstract

&ethods



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10//1

CASTING BETWEEN T"PES Castin! variables is not si&ple. , co&plicated set of rules resolves +a,t,

In so&e cases data is lost and the cast cannot be reversed In others an e9ception is provo$ed

Co&ple9 +%n!er,i%n,are often reJuired

Di..erent T4e, %. T4e Ca,tin2 %r T4e C%n!er,i%n

I/li+it +%n!er,i%n

is bein! done auto&atically by the co&piler and no data %ill be lost. It

includes conversion of a s&aller data type to a lar!er data types and

conversion of derived classes to base class. This is a safe type conversion

E6li+it +%n!er,i%n

E9plicit conversion is bein! done by usin! a cast operator. It includesconversion of lar!er data type to s&aller data type and conversion of base

class to derived classes. In this conversion infor&ation &i!ht be lost or

conversion &i!ht not be succeed for so&e reasons. This is an unsafe type

conversion

5-C#AND .NET 10CS7612N3T 34


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10//1

EPLICIT CONVERSION

E9plicit castin! actually tells the co&piler that %e $no% about possible

infor&ation loss3&is&atch but still %e need to perfor& this cast

This is o$ for inbuilt nu&eric types but in case of reference types- there is a

possibility that the types are not at all co&patible i.e. castin! fro& one type

to another is not at all possible

or e9a&ple castin! a strin! GabcG to Inte!er is not possible

Such castin! e9pressions %ill co&pile successfully but they %ill fail at run

ti&e. Fhat C# co&piler does it that it chec$s %hether these t%o types are

cast co&patible or not and if not it raises an e9ceptionInvalidCastE9ception



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10//1

lon! bi!7u& ? BABB533 E9plicit conversion

int s&allnu& ? *int+bi!7u&5

class 'ase

2

public int nu&4 2 !et5 set5 8

8

class Derived : 'ase2


8

class Pro!ra&

2static void


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10//1

USER7DEFINED CONVERSION

)serdefined conversion is perfor&ed by usin! special &ethods that you

can define to enable e9plicit and i&plicit conversions. It includes

conversion of class to struct or basic data type and struct to class or basic

data type. ,lso- all conversions &ethods &ust be declared as static



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10//1

UPCASTING AND DOWNCASTING

I&plicit conversion of derived classes to base class is called )pcastin! and E9plicit conversion of base class to derived classes is called Do%ncastin!

class 'ase2


8

class Derived : 'ase

2


8

class Pro!ra&

2

static void ar!s+

2

Derived d4 ? ne% Derived*+5

//Upcasting

'ase b4 ? d45

'ase b6 ? ne% 'ase*+5

//Downcasting

Derived d6 ? *Derived+b65

8

8



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10//1

8IS8 AND 8AS8 OPERATORS

%henever %e are usin! e9plicit casts- it is al%ays a !ood idea to

%rap the cast inside a trycatch bloc$. C# also

provides is and as operators %hich are helpful in perfor&in! e9plicit

casts in an e9ception safe &anner

The is operator chec$s %hether the type bein! casted fro& is

co&patible to the type bein! casted to and returns a boolean value



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10//1

EAMPLE

static void ar!s+

2C,SE 4

33 This %ill %or$ fine as o4 is actually an int

ob(ect

o4 ? 45

int i ? *int+o45

33 C,SE 6

33 This %ont %or$ because o6 is not an int so %e need

33 to have an is oprerator before the actual cast ob(ect o6 ? G4G5int (5

if *o6 is int+

2

( ? *int+o65

8

33 C,SE

33 Fe can never $no% %hat is the atual type of 33 an ob(ect at runti&e so its al%ays better to use

33 is operator- re%ritin! the first caseob(ect o ? 45

int $5

if *o is int+

2

$ ? *int+o5

8

8



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Case 4 in the above code snippet %ill thro% an e9ception is o4 is

assi!ned to so&e type that is not int. the other 6 cases are e9ception

safe and %ill only perfor& the cast if the types are co&patible for

castin!

There is one s&all perfor&ance issue in usin! is operator. Case in

above code snippet %ill %or$ fine but it involves accessin! the ob(ect

t%ice. Once for chec$in! the co&patibility i.e. the is operator and

secondly to actually e9tractin! out the value i.e. castin!. can %e not

have so&ethin! li$e GChec$ the co&patibility and if co&patible

perfor& the castG in one sin!le operation



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10//1

9UESTION BAN3


1.Bre%y e8p9a% t$e to p%99ar! o' OOPS % C#,.;%t$ a e8amp9e) E8p9a% utator! ad Acce!!or!.5.;$at %! t$e ame o' ma!ter ode % Sy!tem object< E8p9a% %t$ ae8amp9e!. .E8p9a% 'our met$od parametermod%=er!) %t$ a e8amp9e.

. ;r%te a C# pro"ram to arra"e ame! % a!ced%" order. T$eame! are obta%ed 'rom t$e commad 9%e ar"umet!.

6.E8p9a% t$e 'uct%o! o' Sy!tem. Object c9a!!. >%?e o?err%dedde=%t%o 'or ToStr%"&( ad E@ua9!&(.

7. ;r%te a pro"ram % C# to read a jo""ed array ad d%!p9ay t$e !umo' a99 t$e e9emet! o' t$ree %er array

. E8p9a% Ca!t%" .;%t$ E8amp9e-. ;$at %! 3$er%tace % c# < E8p9a% %t$ !u%tab9e Pro"ram

10. E8p9a% et$od! Ab!tract %t$ c# Pro"ram


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Documents

c# and .net VTU