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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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