CHAPTER 1: INTRODUCTION TO VISUAL BASIC
Describe steps for developing a Visual Basic Application
Use textbox, button, checkbox, label, picturebox, radiobutton.
Explaining about controls and programming
Identify compile errors, run-time errors and logic errors.
INTRODUCING MICROSOFT VISUAL BASIC
What is Visual Basic?
Programming language that allows developers to easily build complex Windows and web
programs, as well as other software tools
Based on the BASIC language
Commonly referred to as VB
What can you do with Visual Basic?
Create applications with graphical windows, dialog boxes, and menus
Create applications that work with databases
Create Web applications and applications that use Internet technologies
Create applications that display graphics
EVENT-DRIVEN COMPUTER PROGRAMS
WITH A GRAPHICAL USER INTERFACE (1 OF 2)
Most Visual Basic 2017 programs are event-driven programs that communicate
with the user through a graphical user interface (GUI)
The GUI usually consists of a window, containing a variety of objects
Defines how elements look and function
An event means the user has initiated an action that causes the program to perform
a type of processing in response to that action
EVENT-DRIVEN
COMPUTER PROGRAMS
WITH A GRAPHICAL USER
INTERFACE (2 OF 2)
For example:
A user might enter
data into the
program and then
click a button
VISUAL STUDIO 2017 WINDOW (1 OF 3)
VISUAL STUDIO 2017 WINDOW (2 OF 3)
The following elements help you to use the Visual Studio 2017 Window:
Title bar: The title bar identifies the window and the application open in the window
Menu bar: The menus contain lists of commands that allow you to create, edit, save, print, test,
and run a Visual Basic program and to perform other functions
Standard tool bar: The Standard tool bar contains buttons that execute frequently used
commands such as Open Project, New Project, Save, Cut, Copy, Paste, and Undo
Toolbox: The toolbox contains .NET components that help you develop the GUI program
Main work area: The main work area contains the item you are currently developing
Solution Explorer: The Solution Explorer window displays the elements of the Visual Basic
solution
OBJECTS MODEL
Visual Basic is an object-oriented programming (OOP) language
Object is an item in a program that contains data and has the ability to perform
actions
The data an object contains is referred to as properties, or attributes
The operations that an object can perform are called methods
Events occur when the user takes action
Classes are templates used to create a new object
OBJECTS MODEL ANALOGY
Class = automobile
Properties of automobile class= make, model, color, engine, year
Object = Each individual auto is an object.
Object is also an Instance of the automobile class.
Methods = start, stop, speedup, slowdown
Events of automobile class = Arrive, Crash
CONTROLS
A control is specific type of object that usually appears in a program’s graphical user
interface
The window that contains the other elements is known as a Form control
The small boxes that accept input are known as TextBox controls
The areas that simply display text are known as Label controls
The buttons that perform operations when clicked with the mouse are known as
Button controls
TYPES OF CONTROLS
Form
Label TextBox
Label TextBox
Label Label
Button Button
VISUAL BASIC CONTROLS
THE NAME PROPERTY
All controls have properties
Each property has a value (or values)
Not all properties deal with appearance
The Name property establishes a means for the program to refer to that control
Controls are assigned relatively meaningless names when created
Programmers usually change these names to something more meaningful
EXAMPLES OF CONTROL NAMES
Form1
Label1 txtHourWorked
Label2 txtPayRate
Label3 lblGrossPay
btnCalcGrossPay btnClose
CONTROL NAMING RULES AND CONVENTIONS
Control names must start with a letter
Remaining characters may be letters, digits, or underscore
1st 3 lowercase letters indicate the type of control
txt… for Text Boxes
lbl… for Labels
btn… for Buttons
After that, capitalize the first letter of each word
txtHoursWorked is clearer than txthoursworked
WRITING VISUAL BASIC PROJECTS
There is a three-step process when writing a Visual Basic application—you set up the user interface,
define the properties, and then create the code.
Planning
Design the User Interface.
Plan the Properties.
Plan the Basic Code; follow the language syntax rules; use pseudocode (English expression or
comment describing action) then you move on to
Programming (and use the same three-step process)
Define the User Interface.
Set the properties.
Write the Basic code.
VBA IDE MODES
Design Time — used when designing the user interface and
writing code
Run Time — used when testing and running a project
Break Time — if/when receiving a run-time error or pause error
** The caption in the titlebar of the VBA IDE indicates which
mode is currently active
PLANNING THE PROJECT
Design the user interface.
Set up the form.
Resize the form.
Place a label and a button control on the
form using the toolbox.
Lock the Controls in place.
After the user interface is designed, the next step is
to set the properties.
SETTING PROPERTIES
Label 1
Name MessageLabel
Text leave blank
Button 1
Name PushButton
Text Push Me
Button 2
Name ExitButton
Text Exit
Form
Name HelloForm
Text Hello World by your name
SETTING THE FORM PROPERTIES
The default startup object is Form1
The name of the form should always
be changed to adhere to naming rules
The properties window shows
the files properties
WRITING THE CODE
While the project is running, the user can perform actions.
Each action by the user causes an event to occur.
Write code for the events you care about; the events you want to
respond to with code.
Code is written as event procedures.
VB will ignore events for which you do not write code.
VB will automatically name event procedures as the object name, an
underscore(_) and the name of the event.
MORE ON WRITING THE CODE
When writing the code for your first project, you will use
the following:
Remark Statement
Assignment Statement
Ending a Program
Editor Window
REMARK STATEMENT
Also known as Comment, used for documentation; every procedure should begin with
a remark statement providing explanation.
Non-executable
Automatically colored Green in Editor
Begins with an apostrophe ( ' )
On a separate line from executable code
At the right end of a line of executable code
'Display the Hello World message.
ASSIGNMENT STATEMENT
Assigns a value to a property or variable
Operates from right to left — the value appearing on the right side of
the equal sign is assigned to the property named on the left of the
equal sign.
Enclose text strings in quotation marks (" ")
MessageLabel.Text=" Hello World "
ENDING A PROGRAM
Methods always have parentheses. (This will help you distinguish them
from Properties which never have parentheses.)
To execute a method of an object you write:
Object.Method()
Current Form may be referenced as Me
Me.Close( )
RUN, SAVE, MODIFY, PRINT, TEST, DEBUG, AND EXECUTE
Run Project
Open Debug Menu, Start Debugging. "Help is always available from the
Help Menu or by pressing F1."
Start Debugging button on the toolbar.
Press F5, the Start Debugging command.
Save Project — File Menu, Save All.
Modify Project if needed.
Print the Code.
Correct any Errors and Rerun.
When you start executing your program, the first step is called compiling, which
means that the VB statements are converted to Microsoft Intermediate Language
(MSIL).Your goal is to have no errors during the compile process: a clean compile.
FINDING AND FIXING ERRORS
Syntax Errors
Breaks VB’s rules for punctuation, format, or spelling
Smart editor finds most syntax errors, compiler finds the rest.
The editor identifies a syntax error with a squiggly blue line and you can point to an error to
pop up the error message.
You can display the Error List window and line numbers in the source code to help locate the
error lines.
Run-Time Errors
Statements that fail to execute, such as impossible arithmetic operations
Logic Errors
Project runs, but produces incorrect results.
END OF CHAPTER 1
