fundamentals of programming in vb 1

7/31/2019 Fundamentals of Programming in VB 1

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Fundamentals of

Programming in Visual Basic

Part 1Robert Burtch

Surveying Engineering Department

Ferris State University

VISUAL BASIC OBJECTS

VB programs display Windows style

screen called a form

Contains boxes and buttons called controls

Forms and controls called objects


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VISUAL BASIC OBJECTS To start click on Microsoft Visual Studio.NET

option Opens Visual Studio start page

START

PROJECT VB.Net also known asapplication, solution orproject

Each project saved as series of

files and subfolders in it own

folder

Start project:

click on File|New|Project

Alternatively, click New Project

icon


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START PROJECT Opens New Project

dialog Select Visual Basic

Projects as Project

Type

Windows Application

as Template

Select name

default

WindowsApplication

with number

Select Location

recommend special

folder

Click OK this will open the

initial VB.NET screen

INITIAL VB SCREEN


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INITIAL VB SCREEN Menu bar

Displays commands used with VB File, Edit, Project, Format,

Debug, etc. Like other windows programs, but some specific to VB

Toolbar Collection of icons that carry out standard operations

Little information rectangle that pops up called a tooltip

Main Area Holds Windows Form Designer

Large stippled Form Window, or Form, becomes Window onexecution

Solution Explorer Window Sometimes used to open programs stored on hard drive

Properties Window Used to change how objects look and read

Toolbox Controls that can be placed on Form

TEXT BOX CAPABILITIES

Double click text box icon

Opens rectangle with sizinghandles in center of form

If handles are displayed objectis said to be selected

Rectangle can be resized bymoving mouse to one of thehandles

Rectangle can be moved byholding down the left mousekey anywhere within theobject


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CREATING TEXT BOX

Alternative

approach

Click on text box

icon

Move mouse to

any place in form

Hold down left

mouse button and

drag a diagonal to

create rectangle

Textbox Cursor

TEXT BOX

Alphabetic tab display Categorized tab

display

To access Properties window, click on Properties

window icon in Toolbar or click on the Properties

window or press F4


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TEXT BOX

Click on Text option in Properties menu In right column, add desired text

Text changes in both the Settings box and

text box

TEXT BOX Highlight property ForeColor to change

color of text (alternatively,press Shift-

Ctrl+F to go to first property beginning

with F)


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TEXT BOX Highlight Font property with single click

of mouse Click on ellipsis () to open Font dialog

box

PROGRAM EXECUTION

To execute

program, click on

Start icon

Example ofexecuted form

Text displayed insingle line to right hides text to left


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TEXT BOX

In Properties window, turnon Multiline option

Result is that

words wrap

Can make Text

box read only:

Properties|ReadOnly

Property|True

TEXT BOX

Can create multiple text boxes in the

form

One with cursor is the active box and this

is called the focusfocus


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COMMAND BUTTON

Double click on Button icon in

Toolbox

Creates a Button on form

Can be manipulated, like the text

box

Button

Cursor

COMMAND BUTTON Click on Caption in Properties window

and type in a new caption for the

command button

Text added to button at same time added

to Properties window


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COMMAND BUTTON

Command buttonlook at execution

Button appears to

move in and out

Will add code tobutton

Can underline parts ofcommand button text by

adding ampersand to text

Here, P is called the

access key pressing

Alt+P activates program

like clicking on command

button

LABELS

Double click on label icon

Places label at center of form

Label Cursor


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LABELS

Alignment canbe changed by

double clicking

Alignment

property in

Properties

window

Executing

program doesnothing to label

Just sits there

User cannot

change what a

label displays

LISTBOX

Click ListBox icon

Click and drag

location of listbox

ListBox displayedon Form


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NAME PROPERTY

Every control has name property Used in code to refer to control

Name must start with letter

Max of 215 characters

Can include numbers and underscore

Cannot include punctuation or spaces

SUGGESTED NAMING CONVENTION

Hungarian notation: 3-letter prefix identifying the type of

control

FrmProgram1frmForm

txtAddresstxtText box

lstOutputlstList box

lblInstructionslblLabel

btnComputeTotalbtnButton

EXAMPLEPREFI

X

CONTROL


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HELP WALKTHROUGH

Dynamic help

Displays list of topics appropriate for what youare working on

To Invoke: Alt | H | H

Help Index

Alphabetized list of all help topics

To Invoke: Alt | H | I

FONTS Default Microsoft Sans Serif


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FONTS Courier New

Fixed-width font

Useful to arrange

columns

Wingdings

Assorted smallpictures and symbols

AUTOHIDE

Pushpin vertical

AutoHide disabled

Pushpin horizontal

AutoHide enabled

Allows you to make more room for Main area of screen by

minimizing tool windows


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When opening/closing

programs use Open

Solution and Close

solution from File

Menu

Do not use Open and

Close

USEFUL PROPERTIES

BackColor

Specified background color for form orcontrol

Visible

When False, causes objects to disappearwhen program is run

Can be made to reappear with code

Enabled

When False, restricts its use

Appears grayed and cannot receive focus


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VISUAL BASIC EVENTS

Event

Action by user such as clicking a control

or pressing a key

Programmer writes code to do something

when event occurs

3 steps in creating a VB program

1. Create interface generate, position, size

objects

2. Set properties configure appearance of

objects

3. Write code that executes an event

VB.NET EVENTS Properties of controls changed using following

form

controlName.property = setting

controlName = name of control

Property = one of controls properties

Setting = any valid setting for control property

Examples

txtBox.ForeColor=Color.Red Changes characters in text box to red txtBox.Text = Hello

Words Hello displayed in text box

btnButton.Visible=True Makes button visible


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EVENT PROCEDURE

Statements executed when even occurs

written in block of code called eventprocedure

First line of Event Procedure has form(sometimes called Procedure-DeclarationStatement)Private Sub objectName_event (ByVal sender As

System.Object, ByVal e As System.EventArgs)Handles objectName.event

Often simplified as

Private Sub ojbectName_event() HandlesobjectName.event

statements

End Sub

KEYWORDS

Words like Private, ByVal, As,

Handles and End keywords or

reserved words

VB.NET automatically capitalizes first letters

of keywords and displays it in blue


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EVENT PROCEDURE

WALKTHROUGH

RedTextbtnRed

(blank)TexttxtSecond

(blank)TexttxtFirst

Demonstratio

n

TextForm1

SETTINGPROPERTYOBJECT

Create a Form with 2 text boxes and one button

Change the properties of the controls

EVENT PROCEDUREWALKTHROUGH


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EVENT PROCEDURE

WALKTHROUGH Code window

Right click anywhere on Main area and

select View Code from pop-up

Page tabs between Code window and Form

Design window

Method Name Box

Class Name Box

EVENT PROCEDUREWALKTHROUGH Rectangular area corresponds to

collapsed block of code

Hover cursor to see information about it


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EVENT PROCEDURE

WALKTHROUGH

To enter code, double click on control Program will automatically take you to

Code window and will enter the first and

last line for the event procedure

First line: Private Sub

Last line: End Sub

Will write code between these two lines

Alternatively, click on Class Name box

and select control

EVENT PROCEDURE WALKTHROUGH Class Name Box

Then select desired option in Method

Name Box


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EVENT PROCEDURE

WALKTHROUGH When typing code, feature called Member Listing will

display properties after typing a period after the control

One proper method highlighted, press Tab key to select

Line of code where

typing is occurring

EVENT PROCEDUREWALKTHROUGH Demonstration code

Run program

Type Hello in

first box

Typedcharacters

appear in Blue


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EVENT PROCEDURE

WALKTHROUGH

Press Tab key tochange focus to

second text box

changes text to black

Click on button to

change text to red

EVENT PROCEDUREWALKTHROUGH

Click back to first text box and add text

Changes color back to blue


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EVENT PROCEDURE

WALKTHROUGH

Adding

a Quit

button

VB.NET EVENTS Name of event procedure can be

changed since the Handles

objectName.event identifies the event

triggering the procedure


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NUMBERS

Numbers called numeric literals

One method of displaying number is with list

box

lstBox.Items.Add(n)

Number n is displayed

Add is called a method carries out operation and

displays result

Another important method is Clear

lstBox.Items.Clear()

Erases all items displayed in lstBox

NUMBERS Example showing different arithmetic

operations to numbers 3 and 2


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NUMBERS

10

1

= 10102 = 100

103 = 1,000

10n = 10000

n zeros

10

-1

= 1/10 = 0.110-2 = 0.01

10-3 = 0.001

10-n = 0.00001

n digits

MM

Following forms of number all equivalent

1.4*10^9 1.4E+9 1.4E9 140000000

3*10^-7 3E-7 0.0000003

NUMBERS Example use of scientific notation


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WITH BLOCK

Reduces repetitive typing and makesprogram less cluttered

Expression starting with period evaluated asif lstResults.Items preceded it

NUMBERS Variables quantities identified by name

Can assign a number to a variable in the

general form:

var = n

Example: if a car travels at 50 miles per hour,

how far will it travel in 14 hours? Also how

many hours are required to travel 410 miles?

Solution uses formula:

elapsedtime*speeddistance =


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NUMBERS

Example solution

Variables: speed, timeElapsed, distance

DECLARING A VARIABLE Dim statement declares the type of variable

Dim varName As Double Declares the variable varName as a double

precision real number

Can declare a variable and assign an initialvalue at same time

Dim varName As Double = 50 Declares varName as double precision and

assigns it a value of 50

Can display the current value of a variableand display it in list box using:

lstBox.Items.Add(varName)


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NUMBERS

Example using default value of variableand value of an expression

BUILT-IN MATH FUNCTIONS VB has some built in math functions that take

one or more input values and returns a single

output

Example:

Math.Round(2.317,1) is

2.3

Int(-2.7) is -

3

Math.Sqrt(2) is

1.414214

Math.Round(2.317,2) is2.32

Int(3) is 3.Math.Sqrt(0) is 0.

Math.Round(2.7) is 3Int(2.7) is 2.Math.Sqrt(9) is 3.


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BUILT-IN MATH FUNCTIONS

Example ofbuilt-in

functions in

Member listing

BUILT-IN MATH FUNCTIONS

When typing, instruction box is

displayed describing the variables

needing input


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NUMBERS

Example evaluates each function for n

NUMBERS

Example evaluates functions at an

expression


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NUMBERS

Integers are declared using thefollowing form

Dim varName As Integer

A single Dim statement can be used to

declare multiple variables

Dim a, b As Double

Dim a As Double, b As IntegerDim c As Double = 2, b As Integer = 5

TYPES OF ERRORS

Syntax errors

Due to misspellings, omissions, orincorrect punctuations

Mostly spotted by editor

Runtime errors

Errors occurring while program is running

Green triangle will appear at left side of lineof code causing the error

Logical errors

Program does not perform in way it wasintended

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