Object-oriented programming 2-Prefinal.pptx

8/10/2019 Object-oriented programming 2-Prefinal.pptx

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OBJECT-ORIENTED

PROGRAMMING2

Introduction to Object-OrientedProgramming


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WHAT YOU WILL LEARN IN THIS

CHAPTER

What object-oriented programming is

How to use OOP techniques

How desktop applications rely on OOP


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What Is a Class?

When you definea class, you definea blueprint for adata type or

object A class definition

starts with thekeyword class

followed by theclass name; andthe class body,enclosed by a pairof curly braces.


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public int MyIntProp

{

get

{

// Property get code.}

set

{

// Property set code.

}

}

// Field used by property.

private int myInt;

// Property.

public int MyIntProp

{

get{

return myInt;

}

set

{

// Property set code.}

}


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Member Functions and Encapsulation

Member variables areattributes of an object and they

are kept private to implement

encapsulation. These variables

can only be accessed using the

public member functions.

A member function of a class

is a function that has its

definition or its prototype

within the class definition like

any other variable. It operates

on any object of the class ofwhich it is a member, and has

access to all the members of

a class for that object.


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Access Modifiers for Class Definitions

MODIFIER DESCRIPTION

none or internal Class is accessible only from within the current

project

public Class is accessible from anywhere

abstract or internal abstract

Class is accessible only from within the current

project, and cannot be instantiated, only derivedfrom

public abstract

Class is accessible from anywhere, and cannot be

instantiated, only derived from

sealed or internal sealed

Class is accessible only from within the current

project, and cannot be derived from, only

instantiated

public sealed

Class is accessible from anywhere, and cannot be

derived from, only instantiated


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public abstract class MyClass

{

// Class members, may be abstract.

}

public sealed class MyClass

{

// Class members.

}

internal class MyBase{

// Class members.

}

virtual The method can be overridden.

abstract The method must be overridden

in non-abstract derived classes (only permitted

in abstract classes).

override The method overrides a base

class method (it must be used if a method is

being overridden).

extern The method definition is found

elsewhere.


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Constructors

A class constructor isa special memberfunction of a classthat is executedwhenever we createnew objects of thatclass.

A constructor willhave exact samename as the class andit does not have anyreturn type. Followingexample explains the

concept ofconstructor:


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Destructors A destructoris a special

member function of aclass that is executedwhenever an object ofits class goes out ofscope. A destructorwillhave exact same nameas the class prefixed

with a tilde (~) and itcan neither return avalue nor can it take anyparameters.

Destructor can be veryuseful for releasingresources beforecoming out of theprogram like closingfiles, releasingmemories etc.Destructors cannot beinherited or overloaded.


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Static and Instance Class Members

As well as having members such as properties,methods, and fields that are specific to objectinstances, it is also possible to have static (also knownas shared)

Static members are shared between instances of aclass, so they can be thought of as global for objectsof a given class. Static properties and fields enableyou to access data that is independent of any objectinstances, and static methods enable you to execute

commands related to the class type but not specific toobject instances. When using static members, in fact,you donteven need to instantiate an object.


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Inheritance

allows us to define a class in terms of another class,which makes it easier to create and maintain anapplication. This also provides an opportunity to reusethe code functionality and fast implementation time.

In OOP terminology, the class being inherited from(derived from) is theparent class (also known as thebase class)

Inheritance enables you to extend or create more

specific classes from a single, more generic base class.


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InheritanceThe syntax used in C# for creating derived classes is as follows:

class { ... }

class :

{ ... }


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Polymorphism

All objects instantiated from a derived class canbe treated as if they were instances of a parentclass.

often expressed as 'one interface, multiplefunctions'.

Polymorphism can be static or dynamic. In staticpolymorphism the response to a function is

determined at the compile time. In dynamicpolymorphism , it is decided at run-time.


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Static Polymorphism

The mechanism of linking a function with an

object during compile time is called early

binding. It is also called static binding. C#

provides two techniques to implement staticpolymorphism. These are:

Function overloading

Operator overloading


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Operator Overloading

You can redefine oroverload most of thebuilt-in operatorsavailable in C#. Thusa programmer canuse operators with

user-defined types aswell. Overloadedoperators arefunctions with specialnames the

keyword operatorfollowed by the symbolfor the operatorbeing defined


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Dynamic Polymorphism

C# allows you to create abstract classes that are used toprovide partial class implementation of an interface.Implementation is completed when a derived classinherits from it. Abstract classes contain abstractmethods, which are implemented by the derived class.

The derived classes have more specialized functionality. Please note the following rules about abstract classes:

You cannot create an instance of an abstract class

You cannot declare an abstract method outside an abstractclass

When a class is declared sealed, it cannot be inherited,abstract classes cannot be declared sealed.


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Dynamic Polymorphism

When you have a functiondefined in a class that youwant to be implemented in aninherited class(es), youuse virtualfunctions. The

virtual functions could beimplemented differently indifferent inherited class andthe call to these functions willbe decided at runtime.

Dynamic polymorphism isimplemented by abstractclassesand virtual functions.


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Interfaces

is a collection of public instance (that is, nonstatic)methods and properties that are grouped together toencapsulate specific functionality.

describes the behavior or capabilities of a C# class

without committing to a particular implementation ofthat class.

define properties, methods and events, which are themembers of the interface. Interfaces contain only thedeclaration of the members. It is the responsibility of

the deriving class to define the members. It oftenhelps in providing a standard structure that thederiving classes would follow.


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OOP TOOLS IN VISUAL STUDIO

The Class View WindowThis window shows you the class hierarchy

of your application and enables you to see at a

glance the characteristics of

the classes you use.


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The Object Browser

The Object Browser is an expanded version of the Class View window,

enabling you to view other classes

available to your project, and even external classes.


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Class DiagramsOne powerful feature of VS that you havent looked at yet is the

capability to generate class diagrams from code and use them to

modify projects. The class diagram editor in VS enables you to

generate UML-like diagrams of your code with ease.

Features:

Classes are shown as blue boxes, including their name and type.

Interfaces are shown as green boxes, including their name and

type.

Inheritance is shown with arrows with white heads (and in some

cases, text inside class boxes).

Classes implementing interfaces have lollipops.

Abstract classes are shown with a dotted outline and italicized

name.

Sealed classes are shown with a thick black outline.


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CLASS LIBRARY PROJECTS

A project that contains nothing but classes (along with other relevant type definitions,

but no entry point) is called a class library.

Class library projects compile into .dll assemblies, and you can access their contents

by adding references to them from other projects


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OBJECT-ORIENTED

PROGRAMMING2

Basic Desktop Programming


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Basic Desktop Programming

WHAT YOU WILL LEARN IN THIS CHAPTERHow to use the WPF designer

How to use controls for displaying information to the user, such as the

Label and TextBlock controls

How to use controls for triggering events, such as the Button control

How to use the controls that enable users of your application to enter text,

such as the TextBox control

How to use controls that enable you to inform users of the current state

of the application and allow the user to change that state, such as the

RadioButton and CheckButton controls

How to use controls that enable you to display lists of information, such as

the ListBox and ComboBox controls

How to use panels to lay out your user interfaces


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Ways to create user interface in Visual Studio Windows Forms

basic tool for creating applications that target classicWindows

use Windows Presentation Foundations (WPF)

provide a wider range of application types and attempts tosolve a number of problems with Windows Forms

is technically platform-independent, and some of its

flexibility can be seen in the fact that a subset of WPFcalled Silverlightis used to create interactive webapplications


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VS Tools in GUI Design

Window Designer

heart of the development of most graphical

Windows applications

In Windows Form, it is used to create a userinterface by dragging and dropping controls from

a Toolbox to your window, placing them where

you want them to appear when you run the

application

In WPF, the user interface can be done by

dragging and dropping controls with writing raw

XAML.


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XAML

Extensible Application Markup Language (XAML, pronounced

zammel)

a language that uses XML syntax

(Extensible Markup Language (XML) is a technology for

storing data in a simple text format and use by .NET, from

describing the configuration of applications to

transporting information between web services)

and enables controls to be added to a user interface in a

declarative, hierarchical way

you can add controls in the form of XML elements, and

specify control properties with XML attributes.

a powerful way to declare user interfaces, it is not a

programming language


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XAML

XAML is designed with todays powerful graphics cards in mind,and as such it enables you to use all the advanced capabilities thatthese graphics cards offer through DirectX. The following listssome of these capabilities:

Floating-point coordinates and vector graphics to provide layout thatcan be scaled, rotated, and otherwise transformed with no loss ofquality

2D and 3D capabilities for advanced rendering

Advanced font processing and rendering

Solid, gradient, and texture fills with optional transparency for UIobjects

Animation storyboarding that can be used in all manner of situations,including user-triggered events such as mouse clicks on buttons

Reusable resources that you can use to dynamically style controls


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XML Sample Code

Beginning Visual C# 2012

Karli Watson

7582

Professional C# 2012

Simon Robinson

7043


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XAML SAMPLE CODE


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WPF Controls

Controls combine prepackaged code and a

GUI that can be reused to create more

complex applications.

They can define how they draw themselves

by default and a set of standard behaviors.

Example: Label, Button, and TextBox controls


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Adding Controls to a Window

Example

Add controls to the Design View by draggingthem from the Toolbox panel or by typing theXAML manually.

Start by dragging a Button control from the Toolboxonto the Design View. Notice how the text in theXAML View is updated to reflect the change youmade.

Now drag another Button, but this time drop it in the

XAML View below the first Button, but above the tag.


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Properties

all controls have a number of properties that are usedto manipulate the behavior of the control. Example;height and width

Dependency Properties

property that is registered with the WPF property systemin such a way as to allow extended functionality. Thisextended functionality includes, but is not limited to,automatic property change notifications.

Attached Properties is a property that is made available to each child object of

an instance of the class that defines the property.


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Manipulating Properties1. Start by selecting the second Button control in Design View;

this is the button that is currently filling the entire window.

2. You can change the name of the control in the Properties

panel at the very top. Change it to rotatedButton.

3. Under the Common node, change the Content to 2nd Button.

4. Under Layout, change width to 75 and height to 22.5. Expand the Text node and change the text to bold by clicking

the B icon.

6. Select the first button and drag it to a position above the

second button. Visual Studio will assist with the positioning by

snapping the control.7. Select the second button again, and hover the mouse pointer

over the top-left corner of it. The pointer changes to a quarter-

circle with arrows on both ends. Drag down until the button is

tilted down.


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Manipulating PropertiesThe XAML code for the window should now look like this:


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Events


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Handling Events

two basic ways to add a handler for an event.

use the Events list in the Properties window

type the name of the event directly in XAML and add the

name of the handler there.


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Routed Events

WPF uses events that are called routed events. Astandard .NET event is handled by the code that hasexplicitly subscribed to it and it is sent only to thosesubscribers. Routed events are different in that theycan send the event to all controls in the hierarchy inwhich the control participates bobbling event- event travels up the control hierarchy

Ex. ButtonGridWindow

tunneling event - event travel in the other direction, that

is, from the root element to the control on which theaction was performedand by convention all events likethis are prefixed with the word Preview

Ex. PreviewMouseButtonDown event


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Control Types

Two Types

Content controls,

a control that have Content property, such as the

Button control,

Items control,

a control that allows you to insert multiple controls as

content. Example: Grid control.


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CONTROL LAYOUT All content layout controls derive from the abstract Panelclass. This class

simply defines a container that can contain a collection of objects that derivefrom UIElement. All WPF controls derive from UIElement.

You cannot use the Panel class directly for control layout, but you can derive

from it if you want to.

Alternatively, you can use one of the following layout controls that derive

from Panel: CanvasThis control enables you to position child controls any way you see fit. It doesnt

place any restrictions on child control positioning, but nor does it provide any assistance in

positioning.

DockPanelThis control enables you to dock child controls against one of its four edges.

The last child control fills the remaining space.

Grid This control enables flexible positioning of child controls. You can divide the layout of

this control into rows and columns, which enables you to align controls in a grid layout.

StackPanelThis control positions its child controls in a sequential horizontal or vertical

layout.

WrapPanel This control positions its child controls in a sequential horizontal or vertical

layout as StackPanel, but rather than a single row or column of controls,


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Stack Order

When a container control contains multiple child controls,

they are drawn in a specific stack order.

The first child in a container is placed on the lowest layer

in the stack, and the last child on the topmost layer.

Alignment, Margins, Padding, and Dimensions

Alignment determine how the control is aligned. Two

alignment properties, HorizontalAlignment (Left, Right,

Center, or Stretch)and VerticalAlignment (Top, Bottom,

Center, or Stretch),

Margin and Padding specify the space to leave blank

around the edges of controls and inside the edges of

controls, respectively.


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Border

control is a very simple, and very useful, container

control. It holds a single child, not multiple children

Canvas provides complete freedom over control positioning

and the HorizontalAligment and VerticalAlignment

properties used with a child element will have no

effect whatsoever over the positioning of thoseelements.


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Canvas


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StackPanel

slimmed down version of DockPanel, where

the edge to which child controls are docked is

fixed for those controls.


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WrapPanel

essentially an extended version of

StackPanel; controls that dont fi t are

moved to additional rows (or columns).


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Grid

Grid controls can have multiple rows and columns that you can use to lay out child controls.You have used Grid controls several times already in this chapter, but in all cases you used a

Grid with a single row and a single column. To add more rows and columns, you must use

the RowDefinitions and ColumnDefinitions properties, which are collections of

RowDefinition ,respectively, and are specifi ed using property element syntax:

Th I C t l


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The Image Control

Image is a very simple control that can be

used to great effect. It allows you to display asingle image and to resize this image as you

see fit. The control exposes two properties,


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The Button Control

This control is used everywhere and is easily

recognized on a user interface

The button does not contain any properties to

display images or text, but you can use the Contentproperty to display simple text or embed an Image

control in the content to display an image


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The TextBox Control These controls are designed exclusively for displaying text to the

user. The TextBox control allows the user to type text into the

application.


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The CheckBox Control

CheckBoxes present the users with options

that they can select or clear. You should use a

CheckBox if you have want to present an

option to the users that can be turned on oroff, or want the users to answer yes or no to

a question.


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The RadioButton Control

RadioButtons are used with other RadioButtons to

allow users to choose between multiple options

where only one can be selected at any time. You

should use RadioButtons when you want the users

to answer a question that has a very limited number

of possible values.


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The ComboBox Control

ComboBoxes are commonly used to displaylong lists of values and allow users to selectexactly one option in a drop-down list.

A ComboBox can be changed to display itselfwith a TextBox at the top that allows theusers to type any values that they feel aremissing.

A ComboBox is an Items control, whichmeans that you can add multiple items to it.


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ComboBox Properties


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The TabControl

It is a layout control that is used to groupcontrols on pages that can be selected byclicking on them.

Tab controls are used when you want to displaya lot of information in a single window but dontwant to clutter the view too much. In this case,you should divide the information into groups of

related items and create a single page for eachgroup.


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The ListBox Control

ListBoxes often allows the user to select

multiple items and display its content in a list

that is always expanded


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Object-oriented programming 2-Prefinal.pptx