Bài giảng Lập trình C# 2010: Chương 5 - ĐH Công nghệ Đồng Nai

DONG NAI UNIVERSITY OF TECHNOLOGY


DONG NAI UNIVERSITY OF TECHNOLOGY


DONG NAI UNIVERSITY OF TECHNOLOGY

Abstraction
Encapsulation
Inheritance
Polymorphism


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Abstraction
Characteristics
Properties
Object
Behaviors
 Methods


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Encapsulation
Characteristics
Properties

Behaviors

 Methods

Package


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Encapsulation
private
protected
public


Inheritance

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• The ability to create a new class
from an existing class
• The existing class is called the
base, superclass, or parent
• The inherited class is called the
derived, subclass, or child
• A derived class has an “is a”
relationship with its base class


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Inheritance

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Inheritance
• Inheritance supports reusability
• Reusability – creation of object
functionality that may be used in multiple
projects


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Polymorphism
• Methods with identical names have
different implementations
• The Select method is different for radio
buttons, check boxes, and list boxes
• Allows a single class to have more than
one method with different argument lists


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How to create Class


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Class Name

Constructors
Attributes
Properties
Methods


public abstract class CAbstractProduct
{ private string m _strID ;
private string m _strN am e;
private string m _strD escription;
public CAbstractProduct() { }
public string ID
{
get { return this.m _strID ; }
set { this.m _strID = value; }
}
public string N am e
{
get { return this.m _strN am e; }
set { this.m _strN am e = value; }
}
public string D escription
{
get { return this.m _strD escription; }
set { this.m _strD escription = value; }
}
public abstract void doSom ething();
}

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Attributes
Constructor

Properties

Methods


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public class CProduct : CAbstractProduct
{
private double m _dPrice;
public CProduct()
{}
public double Price
{
get { return this.m _dPrice; }
set { this.m _dPrice = value; }
}
public override void doSom ething()
{
throw new N otIm plem entedException();
}
}


public class CBook:CProduct
{

private string m _strISBN ;
private string m _strAuthor;
private string m _strTitle;
public CBook()
{
}
public string ISBN
{
get { return this.m _strISBN ; }
set { this.m _strISBN = value; }
}
public string Author
{
get { return this.m _strAuthor; }
set { this.m _strAuthor = value; }
}
public string Title
{
get { return this.m _strTitle; }
set { this.m _strTitle = value; }
}
}

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public class CCom pactD isc:CProduct
{

private string m _strArtist;
private string m _strTitle;
public CCom pactD isc()
{}
public string Artist
{
get { return this.m _strArtist; }
set { this.m _strArtist = value; }
}
public string Title
{
get { return this.m _strTitle; }
set { this.m _strTitle = value; }
}
public override void doSom ething()
{
throw new N otIm plem entedException();
}
}


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public class CTravelG uide:CBook
{
private string m _strCountry;
public CTravelG uide()
{}
public string Country
{

get { return this.m _strCountry; }
set { this.m _strCountry = value; }
}
}


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Garbage Collection


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• Operator new allocates memory
• When objects are no longer referenced, the
CLR performs garbage collection
• Garbage collection helps avoid memory leaks
(running out of memory because unused
memory has not been reclaimed)
• Allocation and deallocation of other resources
(database connections, file access, etc.) must be
explicitly handled by programmers


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• Use finalizers in conjunction with the garbage
collector to release resources and memory
• Before garbage collector reclaims an object’s
memory, it calls the object’s finalizer

• Each class has only one finalizer (also called
destructor)
• Name of a destructor is the ~ character,
followed by the class name
• Destructors do not receive any arguments


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public class CTravelG uide:CBook
{
private string m _strCountry;
public CTravelG uide()
{}
public string Country
{
get { return this.m _strCountry; }
set { this.m _strCountry = value; }
}
~ CTravelG uide()
{
Console.W riteLine("deconstructor");
}
}


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