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Introduction to Visual Basic

Language developed for special-purpose Windows applications – 1991

Uses IDE – Integrated Development Environment

Code based on Q-BasicEvent DrivenPrebuilt graphical components

(controls)

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Two Time Frames

Design Time – when application is being built

Run Time – when application is actually functioning

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Steps in building a VB Application

1. Create the GUI

2. Set the properties for all controls

3. Write the code

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1. Creating the GUI

Form – container for different components of the interface Becomes window on desktop at Run time Shows grid for aligning controls at Design

time – measured in TWIPS (1/1440 in) Graphical elements placed on Form called

Objects or Controls Controls can be added (& properties

changed) during Design & during Run times

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Opening a Project

To open a new project, use the File menu’s New Project command.

To open an existing project, click the Open Project button on the Standard toolbar. You also can use the Open Project command on the File menu, or the Ctrl+O key combination.

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Five windows included in the Visual Basic Startup Screen

Main

Form

Toolbox

Project Explorer (Project)

Properties

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Visual Basic startup screen

Toolbox

Form

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Default-size label control added to the form

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Classes and Objects

Each tool in the toolbox represents a class, which is a pattern from which one or more objects, called controls, are created

Each control you create is an instance of the class from which it was created

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Sizing, Moving, and Deleting Controls

You can size, move, and delete a control, as well as set its properties Before you can delete a control, the

control must be selected and the form must be the active window

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Selecting More Than One Control

You can change a property for more than one control at a time Click the first control you want to

select, then Ctrl-Click the remaining controls

Use the mouse pointer selection method

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2. Setting the properties

Properties – attributes of a control (size, color, caption, etc.) Properties Window Default values Form is actually a control itself with

properties

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Project and Properties Windows

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Caption vs Name Property

Caption property the text seen by the user

Name property assigns a name to an object used by the programmer to refer to an

object in code

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Name Property

Must begin with a letterCan contain letters, numbers, and

the underscore character onlyMust not contain punctuation

characters or spacesMust not exceed 40 charactersUse the three-character IDs shown in

Figure 1-10 (lbl, cmd, txt, frm,…etc.)

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3. Writing the Code

Event – action that can occur at run time

Code written in code window – can double click a control at Design time & write code or click on View Code button & select control

Event procedure – the code that tells computer what to do if an event happens

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Open Code Window

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Listing of Properties and Methods

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Editor Tab in the Options Dialog Box

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Saving a Project

Click the Save Project button on the Standard toolbar. Provide a name for the form and the project.

You also can use the Save <filename> As and Save Project As commands on the File menu. However, be sure to save the form before saving the project.

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Starting and Ending a Project

To start a project: Click the Start button on the Standard toolbar. You also can press F5 or use the Start command on the Run menu.

To end a project: Click the End button on the Standard toolbar. You also can use the End command on the Run menu.

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Printing an Application

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Getting Help

Use the Help menu’s Contents, Index, or Search commands.

Click the object, window, property, and so on for which you want help, then press the F1 key.

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MSDN Library Visual Studio 6.0

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Caption Property’s Help Screen

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Making an Executable File

Visual Basic’s compiler translates the application’s code into machine code

The machine code is stored in a file with a .exe extension on its name

Not in working model of VB!

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Debugging Technique

Print the application’s properties (Form As Text) and code.

In the properties printout, look for a property that is not set correctly.

In the code printout, look for an instruction that is either in the wrong object’s Code window or in the wrong event procedure.