ITC2301
VISUAL BASIC WORKSHOP
PART TWO
VB.NET IDE
VB.NET objects
Writing VB.NET code
◦ Toolbox window
contains set of controls which make up a VB
application.
◦ Windows Form designer window
central part of VB. It provides the display area for
the application acts as a container for all the
controls
◦ Properties window
Each object in VB has a set of characteristics called
properties. This window contains the properties
that control the object’s appearance and behaviour.
Object box, Properties list, Description pane,
settings box
◦ Main window
At top of screen. Contains
title bar:
menu bar: displays commands used to build VB application
standard tool bar: quick access to commonly used menu commands
form, label, picturebox, button
demonstration
◦ Adding a control to a form
◦ sizing, moving and deleting a control
◦ setting properties of a control at design time
◦ changing properties for more than one control
Name – uniquely identifies the object in the program
Text– the caption of a button, contents of a text
box or label, the title of a form
Size.Height and Size.Width – the width and height of
the object (dimension in pixels)
Visible – Whether the object should be shown
Font – the face, style, and size of an objects font
BackColor, ForeColor – color of background or
foreground
EachVB.NET Graphical Object has an extensive list
of properties which can be individually set.
Qualities or attributes of an object/graphic-control
Can be changed by programmer
◦ design time – in the ‘properties’ box.
Can be changed by user
◦ run time – e.g. typing into a text box
Dynamically (in code):
ObjectName.PropertyName = Value
◦ TextBox1.Text = “Hello World”
◦ TextBox1.ForeColor = Color.Blue
Properties Window
◦Click object with mouse – updates RHS
panel
◦If not visible, press ‘F4’
Code associated with an event
◦Typed in the code-window
◦e.g. Text1.Visible = True
◦e.g. Button1.Enabled = False
used as a backdrop for other controls
◦ useful properties include:
Name naming convention = frmSomething
Text the text inside the title bar of the form
BackColor no need to type code, just click on three dots
then choose a coloured box
BackgroundImage used to display a graphic as a background
Font sets font style, bold, italics, underline etc
Startpostition determines where the windows form object is
positioned when it first appears on the
screen
Size used to set the ht and width of the form on the
screen (measured in twips (1400 twips ~ 1
inch)
Purpose of label control is to display text
naming convention = lblSomething
◦ useful properties include:
FlatStyle 3d or flat
BackColor colour of background of label
ForeColour colour of text within label
Borderstyle none or fixed single (box around text)
Text the text on the label
Font appearance as applied to the text
Size set label’s height and width
Position set labels x and y co ords on the form
AutoSize True or False (True enables label to
expand with text)
Used to hold an image
naming convention = picBoxSomething
◦ useful properties include:
image used to select an image to place inside
the picBox control (click on three
dots to open an existing image)
SizeMode set whether the chosen picture fills
the entire space of the image control
Size used to set the size of the image
Location used to set the positioning of the image
Used to get input such as text from the user
naming convention: txtSomething
◦ useful properties include:
BorderStyle - Can have a box around text
Enabled - True or False (False means user cannot enter text into
text box)
Font - same as before
Size, Location. - same as before
MultiLine - True or False (True lets user hit return and keep
typing)
ScrollBars - none, vertical, horizontal or both (requires MultiLine to
be True)
Text - displays initial (default) text in text box; used to lighten
burden on user
◦ Always add a label next to a text box to guide the
user in their input.
used to allow user to initiate some coded
behaviour
naming convention= cmdSomething
◦ useful properties include:
Text - the text on the button
Font - font appearance as applied to the
Caption
Size - used to set the size of the button on the
screen
Location - used to set the positioning of the
button on the screen
Enabled - True or False
Reduce the use of the mouse, so
enable speed for user input
Add an ampersand (&) in front of
access key letter in the caption
◦ ie.
E&xit as the caption on a command button
lets the user select the button by hitting
Alt plus x simultaneously
Important for user friendliness
Example of objects
◦ Form, pictureBox, label, command buttons
Example of events (user actions)
◦ click, double click, scroll, keypress
Event procedure (method)
◦ VB.NET instruction, or code that tells an object
how to respond to an event
To run an application
◦ Click Debug then click start or press F5
◦ Visual Studio .NET creates an executeable
file(.exe) that can be run outside the IDE
◦ Demo:
Lets run our application. What happens?
Programming involves understanding the Syntax and
Semantics of a particular programming language, to
form Statements that tell the computer what to do.
Statement
◦ An instruction to the computer (specifically, for the
compiler)
Syntax
◦ The rules for constructing valid statements
Semantics
◦ The meaning or interpretation of a statement
Statements are organised into a source-code file
The source code file is divided into sections:
◦ Class definition
◦ Form Layout information
◦ Global Variables and Constants
◦ New data type
◦ Procedures and Functions
Actions—such as clicking, double-clicking, and
scrolling—are called events
The set of Visual Basic .NET instructions, or
code, that tells an object how to respond to an
event is called an event procedure
You write statements inside an event procedure
to specify the individual steps required for the
input, processing and output.
To help you follow the syntax rules of the
Visual Basic .NET programming language, the
Code Editor provides you with a code template
for every event procedure
The first line in the Code template is called the
procedure header
And the last line is called the procedure footer
A keyword is a word that has a special meaning in a
programming language
The Sub keyword is an abbreviation of the term sub
procedure, which, in programming terminology,
refers to a block of code that performs a specific task
The Private keyword indicates that the procedure can
be used only within the class in which it is defined
VB.NET provides Code Template for each Event Procedure
Example:
Public Class Form1
Inherits System.Windows.Forms.Form
Private Sub btnExit_Click(ByVal sender As
System.Object, ByVal e As
System.EventArgs) Handles btnExit.Click
Me.Close( )
End Sub
End Class
Keywords = Private Sub, End Sub
Object Name = btnExit
Event = Click ()
Me.Close( ) Method
◦ Terminates the current application
◦ The Me in the instruction refers to the current
form
◦ The Close is the method
