Introduction to visual programmi

ngC#

Learning OutcomesLearning Outcomes

In this chapter, you will learn about :

Event-Based Programming

The Event Based Model

Application Programming Interface (API)

Different types of programs

The first program with visual C#

Event Based Programming Event-based programs provide fully functioning

GUIs

An event is initiated by a user action

A program must:

– Correctly assess which specific event has occurred

– Provide the appropriate code to perform an action based on the identified event

Event Based Programming

Event Based Programming Actions that trigger events include:

– Placing the mouse pointer over a button and clicking the left mouse button

– Using the TAB key until the desired button is highlighted with a dotted line then pushing the Enter key

– Pressing an accelerator key

The sequence of events in a program are controlled by the user

Operating system:– Has total control of computer

– Never relinquishes control to any executing programs

Most executing programs spend the majority of their time in a sleep type of mode

When an event occurs:– The operating system passes event information to

the appropriate application

– Permits the application to take action

The Event-Based Model

Visual Studio .NetVisual Studio .Net

controls

designer

Properties,events

GUI Tree StructureGUI Tree Structure

Panel

Button

Form

Label

GUI Internal structure

containers

Panel Button

Form

Label

Components APIComponents API

PropertiesLike member fieldsGet, set E.g. Button1.Text = “Press Me”

MethodsLike member functionsTell component to do somethingE.g. Button1.Show( )

EventsLike callback functionsReceive notifications from componentE.g. Button1.Click(e)

• Non-interactive

• Linear execution

program:

main(){

code;code;code;code;code;code;code;code;code;code;code;code;

}

Typical command line programTypical command line program

Interactive command line program User input commands

Non-linear execution Unpredictable order

program:

main(){

decl data storage;initialization code;

loop{

get command;switch(command){

command1:code;

command2:code;

…}

}}

User input commands

Non-linear execution Unpredictable order

Event callback procs

Typical GUI programGUI program:

main(){

decl data storage;initialization code;

create GUI;register callbacks;

main event loop;}

Callback1() //button1 press{ code;}Callback2() //button2 press{ code;}…

C Sharp (C#)C Sharp (C#) C# was designed specifically for the .NET platform

as a language that would enable programmers to migrate easily to .NET.

C# is object oriented and has access to a powerful class library of prebuilt components.

It has roots in C, C++ and Java, adapting the best features of each.

Microsoft introduced C# along with its .NET strategy in 2000.

The .NET platform allows applications to be distributed to a variety of devices.

The first program

The first program

The purpose of the code is so that you can add your own methods to handle the logic for your application, such as what happens when the user clicks the OK button

The first program

Double click the ok Button on the form. A new method has been added called ok_click. We add the code to the ok_click method

The firstThe first program

The firstThe first program