Chapter03 Object Based Programming

7/27/2019 Chapter03 Object Based Programming

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Chapter 3: Object-Based

Programing

Hoang Anh [email protected]

HaNoi University of Technology

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Microsoft

Overview

“Everything is an object! At least, that is the view

from inside the CLR and the C# programming language.

This is no surprise, because C# is, after all, an object-

oriented language. The objects that you create through

class definitions in C# have all the same capabilities as

the other predefined objects in the system…”

Apress-Accelerated C# 2008

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Roadmap

3.1. Introduction

3.2. Implementing a time Abstract DataType with a class

3.3. Class Scope

3.4. Controlling Access to Members3.5. Initialize Class Objects: Constructors

3.6.Using Overloaded Constructors

3.7. Properties

3.8. Composition: Objects References as InstanceVariables of Other Classes

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Roadmap(2)

3.9. Using the this Reference

3.10. Garbage Collection

3.11. static Class Members

3.12. const and readonly Members3.13. Indexers

3.14. Data Abstaction and Information Hiding

3.15. Software Reusability

3.16. Namespace and Assemplies

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3.1. Introduction

Object orientation uses classes to encapsulate data( attributes) andmethods(behaviors)

Data members: member variables or instance variables

Methods: manipulate the data

Objects are instantiated from classes

Objects have the ability to hide their implementation from other objects( information hiding )

Some objects can communicate with one another across well-defined interfaces

Example:

The driver’s interface to a car includes steering wheel,accelerator pedal, brake pedal and gear shift…

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Roadmap

3.1. Introduction


3.3. Class Scope

3.4. Controlling Access to Members 3.5. Initialize Class Objects: Constructors


3.7. Properties


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3.2. Implimenting a Time Abstract

DataType with a class Classes in C# facilitate the creation of abstract data types(ADT),

hiding their implementation from clients

In procedural programming language: client code is dependent onimplementation details of the data used in the code, ADT’s eliminatethis problem.

Example:

Time1 class

Three in instance variables: hour, minute and second

A constructor: initialzes objects of Time1 class

Method SetTime(): sets the time

Method ToUniversalString(): returns a string in universal-time format Method ToStandardString(): returns a string in standard-time format

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// Class Time1 maintains time in 24-hour format.using System;// Time1 class definition public class Time1 : Object{

private int hour; // 0-23 private int minute; // 0-59 private int second; // 0-59// Time1 constructor initializes instance variables to// zero to set default time to midnight public Time1(){

SetTime( 0, 0, 0 );}// Set new time value in 24-hour format. Perform validity// checks on the data. Set invalid values to zero. public void SetTime(

int hourValue, int minuteValue, int secondValue ){

hour = ( hourValue >= 0 && hourValue < 24 ) ?hourValue : 0;

minute = ( minuteValue >= 0 && minuteValue < 60 ) ? minuteValue : 0;

second = (secondValue >= 0 && secondValue < 60) ?secondValue : 0;} // end method SetTime// convert time to universal-time (24 hour) format string public string ToUniversalString(){

return String.Format("{0:D2}:{1:D2}:{2:D2}", hour, minute, second);

}// convert time to standard-time (12 hour) format string public string ToStandardString(){

return String.Format("{0}:{1:D2}:{2:D2} {3}",((hour == 12 || hour == 0) ? 12 : hour % 12), minute, second, (hour < 12 ? "AM" : "PM"));

}} // end class Time1

Example

Class Time1

inherits from

class Object

Delicate the

body of class

Declare

variables

Member

Access

Modifiers

Constructor

Methods



// Demonstrating class Time1.using System;using System.Windows.Forms;// TimeTest1 uses creates and uses a Time1 objectclass TimeTest1

{// main entry point for applicationstatic void Main( string[] args ){

Time1 time = new Time1(); // calls Time1 constructorstring output;// assign string representation of time to outputoutput = "Initial universal time is: " +

time.ToUniversalString() +"\nInitial standard time is: " +time.ToStandardString();

// attempt valid time settingstime.SetTime( 13, 27, 6 );

// append new string representations of time to outputoutput += "\n\nUniversal time after SetTime is: " +time.ToUniversalString() +"\nStandard time after SetTime is: " +time.ToStandardString();

// attempt invalid time settingstime.SetTime( 99, 99, 99 );output += "\n\nAfter attempting invalid settings: " +

"\nUniversal time: " + time.ToUniversalString() +"\nStandard time: " + time.ToStandardString();

MessageBox.Show(output, "Testing Class Time1");

} // end method Main

} // end class TimeTest1

Example



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Roadmap

3.1. Introduction


3.3. Class Scope

3.4. Controlling Access to Members 3.5. Initialize Class Objects: Constructors


3.7. Properties


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3.3. Class Scope

A class’s instance variables and methods belong to thatclass’s scope

Class members are accessible to methods in that class’sscope and can be referenced by name

Acesses to class members outside:referenceName.memberName

Block scope: Variables declared in a method have block scope

If a block-scope variable has the same name to a class-scopevariable, the class-scope one is hiden( access to that one in themethod using keyword this and dot operator)

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Roadmap

3.1. Introduction


3.3. Class Scope

3.4. Controlling Access to Members

3.5. Initialize Class Objects: Constructors


3.7. Properties


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The visibility of the member is defined by accessibility

keyword

The most common accessibility

public : Public members are visible inside and outside of the

class

private: The visibility of private members is restricted to the

containing class

Property

Controls access to private data get and set properties

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// Demonstrate compiler errors from attempt to access// private class members.

class RestrictedAccess

{

// main entry point for application

static void Main(string[] args)

{Time1 time = new Time1();

time.hour = 7;

time.minute = 15;

time.second = 30;

}

} // end class RestrictedAccess

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Compiler errors

public class Time1 : Object

{

private int hour;

private int minute;

private int second;}



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Roadmap

3.1. Introduction


3.3. Class Scope




3.7. Properties


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3.5. Initialize Class Objects: Constructors Are called when a class is first loaded by the CLR of an object is created

Set up the state of the object by initializing the fields to a desired predefined state

Constructor syntax:

accessibility modifier typename(parameterlist )

Have the same name of the class and never have a return type

Initialize the state of an object

Types of Constructor:• Static Constructor

• Instance Constructor

Called when an instance of a class is created

Can be overloaded

Default constructor:• If a class does not define any constructors, the compiler provides a default( no-argument)

constructor( no code and noparameters)• Can be provided by the programmer. Programmer-provided ones can have code in bodies

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static Constructors

static constructors is used to initialize the values of static data when the value isn’tknown at comple time

A given class (or structure) may define only a single static constructor.

A static constructor does not take an access modifier and cannot take any

parameters.

A static constructor executes exactly one time, regardless of how many objects of thetype are created.

The runtime invokes the static constructor when it creates an instance of the class or before accessing the first static member invoked by the caller.

The static constructor executes before any instance-level constructors.

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class Car

{

// The 'state' of the Car.

public string petName;

public int currSpeed;

// A custom default constructor.

public Car()

{

petName = "Chuck";

currSpeed = 10;

}// Here, currSpeed will receive the

// default value of an int (zero).

public Car(string pn)

{

petName = pn;

}

// Let caller set the full 'state' of the Car.

public Car(string pn, int cs)

{

petName = pn;

currSpeed = cs;

}

..

}

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A custom defaultconstructor

Instance Constructors


{

// Make a Car called Chuck going 10 MPH.

Car chuck = new Car();

chuck.PrintState();

// Make a Car called Mary going 0 MPH.

Car mary = new Car("Mary");

mary.PrintState();

// Make a Car called Daisy going 75 MPH.

Car daisy = new Car("Daisy", 75);daisy.PrintState();

}



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class SavingsAccount

{ public double currBalance;

public static double currInterestRate;

public SavingsAccount(double balance)

{

currBalance = balance;

}

// A static constructor.

static SavingsAccount(){

Console.WriteLine("In static ctor!");

currInterestRate = 0.04;

}

...

}

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static Constructor

static Data



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Roadmap

3.1. Introduction


33. Class Scope




3.7. Properties


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3.6. Using Overloaded Constructors

Constructors can be overloaded

Overloaded constructors may be used to providedifferent ways to initialize objects of a class

Contructors overloading is the process of using the sameContructors name for multiple Contructors

The function resolution of overloaded constructors isdetermined by the parameters of the new statement

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Note:

If multiple contractor match a contractor call, thecompiler picks the best match

If none matches exactly but some implicit conversion

can be done to match a contractor, then thecontractor is invoked with implicit conversion.

A constructor can call another constructor using the

this reference

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using System;

namespace Donis.CSharpBook

{

public class Employee

{

public Employee(string _name)

{

name = _name;}

public Employee(string _first, string _last)

{

name = _first + " " + _last;

}

private string name = "";

}

public class Personnel

{

public static void Main(){

Employee bob = new Employee("Jim", "Wilson"); // 2 arg c'tor

}

}

}

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Overloaded

Constructures

class Employee

{

public Employee()

: this("")

{

}

public Employee(string _name)

{

name = _name;

}public Employee(string _first, string _last)

: this(_first + " " + _last)

{

}

public void GetName()

{

Console.WriteLine(name);

}

private string name = "";

}

Call Employee(string _name)constructor

using the colon syntax



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Roadmap

3.1. Introduction


3.3. Class Scope




3.7. Properties


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3.7. Properties

Used for strict control of access to the internal state of an object

Are get and set methods exposed as properties

Propertiy syntax:

Accessibility modifier type propertyname{ attributes get{getbody}

attributes set{setbody}} Example:

Neither method is called directly

Auto-Implemented Properties

C# 3.0 has a new feature called auto-implemented properties that

reduce this burden significantly.

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using System;namespace Donis.CSharpBook{

public class Person

{ private int prop_age; public int age{

set {// perform validation prop_age=value;}

get { return prop_age; }}

}

class People{ public static void Main(){

Person bob = new Person(); bob.age = 30;

Console.WriteLine(bob.age);}

}

}

Example

age property

Set method

Call gets method

value keyword represents theimplied parameter

// use Auto-Implemented Properties

public class Employee

{

public string FullName { get; set; }

public string Id { get; set; }

}

Use Ato-ImplementedProerties



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Read-only and write-only properties

Read-only property:

Offer only the get method and omit the set method

Write-only property:

Have a set only

Example:

• Password property ( write-only property)

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public class SensitiveForm

{

private string prop_password;

public string password{

set

{

prop_password = value;

}

}

}



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Roadmap

3.1. Introduction


3.3. Class Scope




3.7. Properties


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3.8. Composition: Objects References

as Instance Variables of Other Classes

One form of software reuse is composition, in which a

class has as members references to objects of other

classes.

Example:

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Class Date int instance variables

month

day year

Constructor

public Date( int theMonth, int theDay, int theYear ) Method

ToDateString(): returns the string representation of a Date.

CheckDay()

Class Employee: is composed of two references of type string and two references of class Date

Instance variables firstName

lastName

birthDate

hireDate Methods:

ToEmployeeString(): returns a string containing the name of the Employee and thestring representations of the Employee’s birthDate and hireDate

Class CompositionTest : runs the application with method Main Code:

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References to Date objects

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2 // Date class definition encapsulates month, day and year. 34 using System;5

6 // Date class definition 7 public class Date8 {9 private into month; // 1-12 10 private into day; // 1-31 based on month 11 private into year; // any year 1213 // constructor confirms proper value for month; 14 // call method Check Day to confirm proper 15 // value for day 16 public Date( into theMonth, into theDay, into theYear )

17 {18 // validate month 19 if ( theMonth > 0 && theMonth <= 12 )20 month = theMonth;2122 else 23 {24 month = 1;25 Console.WriteLine(26 "Month {0} invalid. Set to month 1.", theMonth );27 }

2829 year = theYear; // could validate year 30 day = Check Day( theDay ); // validate day 31 }32

Example

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Constructor that receives the month, day andyear arguments. Arguments are validated; if

they are not valid, the corresponding member isset to a default value

E l (2)



Example(2)

32

33 // utility method confirms proper day value

34 // based on month and year

35 private into Check Day( into test Day )

36 {

37 into[] daysPerMonth =38 { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

39

40 // check if day in range for month

41 if ( test Day > 0 && test Day <= daysPerMonth[ month ] )

42 return test Day;

43

44 // check for leap year

45 if ( month == 2 && test Day == 29 &&

46 ( year % 400 == 0 ||

47 ( year % 4 == 0 && year % 100 != 0 ) ) )

48 return test Day;

49

50 Console.WriteLine(

51 "Day {0} invalid. Set to day 1.", test Day );

52

53 return 1; // leave object in consistent state

54 }

55

56 // return date string as month/day/year

57 public string ToDateString()

58 {

59 return month + "/" + day + "/" + year;

60 }

61

62 } // end class Date

Validate that thegiven month canhave a given day

number



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1 2 // Employee class definition encapsulates employee's first name, 3 // last name, birth date and hire date. 45 using System;67 // Employee class definition 8 public class Employee9 {10 private string firstName;

11 private string lastName;12 private Date birthDate;13 private Date hireDate;1415 // constructor initializes name, birth date and hire date 16 public Employee( string first, string last,17 int birthMonth, int birthDay, int birthYear,18 int hireMonth, int hireDay, int hireYear )

19 {20 firstName = first;21 lastName = last;2223 // create new Date for Employee birth day 24 birthDate = new Date( birthMonth, birthDay, birthYear );25 hireDate = new Date( hireMonth, hireDay, hireYear );

26 }27

Two Date objects are membersof the Employee class

Constructor that initializes the employee’sname, birth date and hire date

Example(3)



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28 // convert Employee to String format 29 public string ToEmployeeString()30 {31 return lastName + ", " + firstName +32 " Hired: " + hireDate.ToDateString() +33 " Birthday: " + birthDate.ToDateString();

34 }3536 } // end class Employee

Example(4)



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1 2 // Demonstrate an object with member object reference. 34 using System;5 using System.Windows.Forms;67 // Composition class definition 8 class CompositionTest9 {

10 // main entry point for application 11 static void Main( string[] args )12 {13 Employee e =14 new Employee( "Bob", "Jones", 7, 24, 1949, 3, 12, 1988 );1516 MessageBox.Show( e.ToEmployeeString(),17 "Testing Class Employee" );1819 } // end method Main

2021 } // end class CompositionTest

Example(5)



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Roadmap




3.12. const and readonly Members 3.13. Indexers




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C# supplies a this key word that provides access to the

current class instance

Uses of this keyword

•Resolve scope ambiguity

• Arise when an incoming paramerter is named identically to a

data field of the type

• Design a class using technique termed constructor

chaining

• Helpful when declaring multiple constructors

Example:

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Class Motorcycle

Instance variables

driverIntensity

Name Method

SetDriverName(string)

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class Motorcycle

{

public int driverIntensity;

public string name;

public void SetDriverName(string name)

{ name = name; }...

}

Problem: Theimpementation of

SetDriverName()assigns theincomingparameter backto itself

public void SetDriverName(stringname)

{ this.name = name; }



class Motorcycle{

public int driverIntensity;

public string driverName;// Constructor chaining. public Motorcycle() {} public Motorcycle(int intensity): this(intensity, "") {} public Motorcycle(string name): this(0, name) {}// This is the 'master' constructor that does all the real

work. public Motorcycle(int intensity, string name)

{ if (intensity > 10){

intensity = 10;}driverIntensity = intensity;driverName = name;

}...

}

Example

Constructor chaining



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Roadmap








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One of the key facilities in the CLR is the garbagecollector

GC frees you from the burden of handling memoryallocation and deallocation

The execution environment handles the tracking of object references and distroys the object instances whenthey’re no longer use

Forcing a Garbage Collection: In some situations, it maybe beneficial to programmatically force a garbagecollection using GC.Collect()

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{

...

// Force a garbage collection and wait for // each object to be finalized.

GC.Collect();

GC.WaitForPendingFinalizers();

...

}



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Finalizer( Destructor)

• Returns resources to the system

• Each class can contain only one destructor

• Name:

Is formed by preceding the class name with a ~ charater • Is an override of a virtual method on System.Object

• Has no return type, no access modifiers

• Not inherited

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using System;

public class Base

{

~Base()

{

Console.WriteLine("Base.~Base()");

}

}

public class Derived : Base

{

~Derived()

{

Console.WriteLine("Derived.~Derived()");

}

}public class EntryPoint

{

static void Main()

{

Derived derived = new Derived();

}

}

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Destructor of Base class

Destructor of Derived

class



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Roadmap








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A program contains only one copy of each of a class’s static

variables in memory

A static variable represents class-wide information

The declaration of a static member begins with the keyword static

A static variable can be initialized in its declaration Static members:

• static method

• static data

• static constructor

• static class

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using System; public static class StaticClass{

public static void DoWork(){

++callCount;Console.WriteLine("StaticClass.DoWork()");

} public class NestedClass{

public NestedClass(){

Console.WriteLine("NestedClass.NestedClass()");}

} private static long callCount = 0; public static long CallCount{

get{

return callCount;}

}}

public static class EntryPoint{

static void Main(){

StaticClass.DoWork();// OOPS! Cannot do this!// StaticClass obj = new StaticClass();StaticClass.NestedClass nested =

new StaticClass.NestedClass();Console.WriteLine("CallCount = {0}",StaticClass.CallCount);

}}

Example

static class is a collection

of static membersand can not haveobject instancedfrom

constants and nestedtypes declared

within a static classare static by default

Can not do this



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Roadmap








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3.12.const and readonly Members

Constant Data

Read-Only Field

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constant Data

const syntax: accessibility modifier const constname=initialization;

Are initialized at compile time using a constant

expression and cannot be modified at run time

50

public class ZClass

{

public const int fielda = 5,

fieldb = 15;

// Error public static int fieldd=15;

public const int fieldc = fieldd + 10;

}



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readonly Field

A read-only field cannot be changed after the initial

assignment

The value assigned to a read-only field can be

determined at runtime

51

class MyMathClass

{

public readonly double PI;

public MyMathClass()

{

PI = 3.14;

}// Error!

public void ChangePI()

{ PI = 3.14444; }

}

class MyMathClass

{

// Read-only fields can be assigned in ctors,

// but nowhere else.

public readonly double PI;public MyMathClass()

{

PI = 3.14;

}

}



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Roadmap








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3.13. Indexers

Allow to treat an object instance as if it were an array

Are instance-based and work on a specific instance of an object of the defining class

Cannot pass the results of calling an indexer on anobject as an out or ref parameter to a method as with areal array

this[] syntax

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// Add the indexer to the existing class definition.

public class PeopleCollection : IEnumerable

{ private ArrayList arPeople = new ArrayList();

// Custom indexer for this class.

public Person this[int index]

{

get { return (Person)arPeople[index]; }

set { arPeople.Insert(index, value); }

}

...}

54

static void UseGenericListOfPeople()

{

List<Person> myPeople = new List<Person>();

myPeople.Add(new Person("Lisa", "Simpson", 9));

myPeople.Add(new Person("Bart", "Simpson", 7));

// Change first person with indexer.

myPeople[0] = new Person("Maggie", "Simpson", 2);// Now obtain and display each item using indexer.

for (int i = 0; i < myPeople.Count; i++)

{

Console.WriteLine("Person number: {0}", i);

Console.WriteLine("Name: {0} {1}", myPeople[i].FirstName,

myPeople[i].LastName);

Console.WriteLine("Age: {0}", myPeople[i].Age);

Console.WriteLine();}

}

class Person

{

private string FirstName;

private string LastName;private int Age;

...

}

Indexer iscreatedusingthis[]

syntax

Using indexer to getvalue



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Overloaded Indexer Methods

public sealed class DataTableCollection : InternalDataCollectionBase

{

...

// Overloaded indexers!

public DataTable this[string name] { get; }public DataTable this[string name, string tableNamespace] { get; }

public DataTable this[int index] { get; }

}

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5 using System;6 using System.Drawing;7 using System.Collections;8 using System.ComponentModel;9 using System.Windows.Forms;10 using System.Data;1112 // Box class definition represents a box with length,13 // width and height dimensions 14 public class Box15 {

16 private string[] names = { "length", "width", "height" };17 private double[] dimensions = new double[ 3 ];1819 // constructor 20 public Box( double length, double width, double height )21 {22 dimensions[ 0 ] = length;23 dimensions[ 1 ] = width;24 dimensions[ 2 ] = height;

25 }2627 // access dimensions by index number 28 public double this[ int index ]29 {30 get 31 {32 return ( index < 0 || index > dimensions.Length ) ?33 -1 : dimensions[ index ];

34 }35

Indexer declaration; indexer receives an integer to specify which

dimension is wanted

The get index accessor

If the index requested is out bounds, return – 1; otherwireturn the appropriate eleme

Example

Example(2)



36 set 37 {38 if ( index >= 0 && index < dimensions.Length )39 dimensions[ index ] = value;40 }4142 } // end numeric indexer 4344 // access dimensions by their names 45 public double this[ string name ]46 {47 get

48 {49 // locate element to get 50 int i = 0;5152 while ( i < names.Length &&53 name.ToLower() != names[ i ] )54 i++;5556 return ( i == names.Length ) ? -1 : dimensions[ i ];

57 }5859 set 60 {61 // locate element to set 62 int i = 0;6364 while ( i < names.Length &&65 name.ToLower() != names[ i ] )

66 i++;

Indexer that takes the name of thedimension as an argument

The set accessor for the index

Validate that the user wishes to set a validindex in the array and then set it

Example(2)

E l (3)



68 if ( i != names.Length )69 dimensions[ i ] = value;70 }71

72 } // end indexer 7374 } // end class Box 7576 // Class IndexerTest 77 public class IndexerTest : System.Windows.Forms.Form 78 {79 private System.Windows.Forms.Label indexLabel;80 private System.Windows.Forms.Label nameLabel;81

82 private System.Windows.Forms.TextBox indexTextBox;83 private System.Windows.Forms.TextBox valueTextBox;8485 private System.Windows.Forms.Button nameSetButton;86 private System.Windows.Forms.Button nameGetButton;8788 private System.Windows.Forms.Button intSetButton;89 private System.Windows.Forms.Button intGetButton;9091 private System.Windows.Forms.TextBox resultTextBox;9293 // required designer variable 94 private System.ComponentModel.Container components = null;9596 private Box box;9798 // constructor 99 public IndexerTest()100 {

101 // required for Windows Form Designer support 102 InitializeComponent();

Example(3)

Example(4)



104 // create block 105 box = new Box( 0.0, 0.0, 0.0 );106 }107108 // Visual Studio .NET generated code 109110 // main entry point for application 111 [STAThread]112 static void Main()113 {114 Application.Run( new IndexerTest() );115 }116117 // display value at specified index number 118 private void ShowValueAtIndex( string prefix, int index )119 {120 resultTextBox.Text =121 prefix + "box[ " + index + " ] = " + box[ index ];122 }123124 // display value with specified name 125 private void ShowValueAtIndex( string prefix, string name )126 {127 resultTextBox.Text =128 prefix + "box[ " + name + " ] = " + box[ name ];129 }130131 // clear indexTextBox and valueTextBox 132 private void ClearTextBoxes()133 {134 indexTextBox.Text = "";135 valueTextBox.Text = "";136 }137

Use the get accessor of the indexer

Use the set accessor of the indexer

Example(4)

Example(5)



138 // get value at specified index 139 private void intGetButton_Click(140 object sender, System.EventArgs e )141 {

142 ShowValueAtIndex(143 "get: ", Int32.Parse( indexTextBox.Text ) );144 ClearTextBoxes();145 }146147 // set value at specified index 148 private void intSetButton_Click(149 object sender, System.EventArgs e )150 {151 int index = Int32.Parse( indexTextBox.Text );

152 box[ index ] = Double.Parse( valueTextBox.Text );153154 ShowValueAtIndex( "set: ", index );155 ClearTextBoxes();156 }157158 // get value with specified name 159 private void nameGetButton_Click(160 object sender, System.EventArgs e )161 {162 ShowValueAtIndex( "get: ", indexTextBox.Text );163 ClearTextBoxes();164 }165

Use integer indexer to set value

Use integer indexer to get value

Use string indexer to get value

Example(5)

E l (6)



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166 // set value with specified name 167 private void nameSetButton_Click(168 object sender, System.EventArgs e )

169 {170 box[ indexTextBox.Text ] =171 Double.Parse( valueTextBox.Text );172173 ShowValueAtIndex( "set: ", indexTextBox.Text );174 ClearTextBoxes();175 }176177 } // end class IndexerTest

Before setting value by index number

After setting value by index number

Example(6)



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Before getting value by dimension name

After getting value by dimension name

Before setting value by dimension name

Example(8)



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After setting value by dimension name

Before getting value by index number

After getting value by index number

Example(9)



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Roadmap








64

3 14 D t Ab t ti d I f ti



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3.14. Data Abstraction and Information

Hiding Classes normally hide the details of their implementation

from their clients

Data Abstraction: Example: stack, queue

Abstract Data Type (ADT): the programming-languagescommunity needed to formalize some notions about data

Data representation

Operation

Example:

int is an abstract representation of an integer

65

Information hiding



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Roadmap








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Framework Class Library (FCL):

Contain thousands of predefined classes

Allow to achieve software reusability across platforms that

support

Enable C# developers to build applications faster by reusing

preexisting, extensively tested classes

Include classes for creating Web services

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Roadmap








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3.16. Namespaces and Assembly

Namespace helps to solve naming collision problems

Reusing class definitions between programs

public class can be reused from class libraries

Non- public classes can be used only by other classed in the

same assemply

A dynamic link library represents an assembly

When a project uses a class library, it must contain a

reference to the assembly that defines the class library

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Microsoft

3.16. Namespaces and Assembly(2)

Orthogonal concepts:

namespace for organization

assembly for packaging

One namespace could be spread across multiple

assemblies

One assembly may contain multiple namesspaces

e.g. mscorlib.dll

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Summary

You’ve learned the basic knowledge of object-oriented

programming in C#, including the use of classes and

their members.

You’ve also informed about garbage collection in C#,

how to use information hiding as well as data abstractionin C#

Documents

Chapter03 Object Based Programming