introduction to 1 - hkta tang hin memorial secondary …lwc1/files/s2_cl/vb/vb notes - part...
TRANSCRIPT
A revised course with
- Concise concepts
- Hands on class work
- Plenty of examples
- Programming exercises
Introduction to
Copyright © HKTA Tang Hin Memorial Secondary School 2012-13
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Version 1.1
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Contents
Chapter 1 Ideas of Programming ............................................................................................ 4
1.1 What is a program? ................................................................................................ 4
1.2 What is programming? .......................................................................................... 4
1.3 What is a programming language? ........................................................................ 5
1.4 Compilers ............................................................................................................... 5
1.5 Names of some programming languages .............................................................. 6
Chapter 2 Visual Basic 2010 Express ...................................................................................... 8
2.1 Download Visual Basic 2010 Express ..................................................................... 8
2.2 Register Visual Basic 2010 Express within 30 days ................................................ 8
2.3 Your first project .................................................................................................... 9
2.3.1 Create and save a new project .................................................................. 9
2.3.2 Introduction to Visual Basic 2010 IDE ...................................................... 11
2.3.3 Adding controls and code ........................................................................ 12
2.3.4 Open an existing project .......................................................................... 13
2.4 Structure of a Visual Basic 2010 project .............................................................. 14
2.5 Microsoft Developer Network (MSDN) ............................................................... 14
Chapter 3 Working with Controls ......................................................................................... 15
3.1 Introduction to GUI programming in Visual Basic ............................................... 15
3.2 Controls ................................................................................................................ 15
3.3 Properties window ............................................................................................... 16
3.4 Changing properties at runtime ........................................................................... 17
3.5 Assigning values to properties ............................................................................. 18
3.6 Add a comment to your source code .................................................................. 19
Exercise 3 ......................................................................................................................... 19
Chapter 4 Events and Methods ............................................................................................ 20
4.1 Introduction to events and methods ................................................................... 20
4.2 Events ................................................................................................................... 20
4.2.1 Introduction to event procedures ........................................................... 20
4.2.2 Adding an event procedure in Visual Basic .............................................. 21
4.2.3 Names and types of events ...................................................................... 22
4.2.4 The structure of an event procedure ....................................................... 23
4.2.5 TextChanged events ................................................................................. 23
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4.3 Methods ............................................................................................................... 24
Exercise 4 ......................................................................................................................... 26
Chapter 5 Variables, Input and Output ................................................................................ 27
5.1 Variables............................................................................................................... 27
5.1.1 Declaring variables with Dim statement .................................................. 27
5.1.2 Keywords and names of variables ........................................................... 28
5.1.3 Giving values to variables in the Dim statement ..................................... 28
5.1.4 Declaring several variables in a single line .............................................. 28
5.1.5 Using variables to store values ................................................................ 29
5.1.6 Scope of variables .................................................................................... 30
5.2 Introduction to InputBox and MsgBox ................................................................ 32
5.2.1 InputBox ................................................................................................... 32
5.2.2 MsgBox ..................................................................................................... 33
5.2.3 Miscellaneous examples .......................................................................... 34
Exercise 5 ......................................................................................................................... 34
Chapter 6 Operators and Expressions .................................................................................. 35
6.1 Arithmetic Operators ........................................................................................... 35
6.2 Parentheses (singular: parenthesis) .................................................................... 36
6.3 Concatenation Operators .................................................................................... 36
6.4 Operator Precedence ........................................................................................... 37
6.5 Increment and Decrement ................................................................................... 38
6.6 Val function .......................................................................................................... 38
6.7 Mathematical Constants and Functions .............................................................. 39
6.8 Miscellaneous Examples ...................................................................................... 40
Exercise 6 ......................................................................................................................... 41
Chapter 7 Flow Control (1) ................................................................................................... 42
7.1 Decision Making ................................................................................................... 42
7.2 Relational Operators ............................................................................................ 42
7.3 If...Then...Else Statement ..................................................................................... 43
7.4 Multiple conditions with keyword ElseIf ............................................................. 44
7.5 Official Syntax of If...Then...Else Statement ........................................................ 46
Exercise 7 ......................................................................................................................... 47
Alphabetical Index ................................................................................................................... 48
Introduction to Visual Basic - Book 1
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Chapter 1 Ideas of Programming
1.1 What is a program?
A program is a set of instructions that tells a computer how to do a task. With programs,
computers can perform tasks __________________ and ___________________.
1.2 What is programming?
Programming is the process of designing, writing, testing and debugging (remove mistakes)
a program. To write a program, you need to know and solve the problem first. After
solving the problem, you tell the computer how to solve the problem using a programming
language.
For example, if you need to write a program that calculates percentage changes, you
should first solve the problem by obtaining the formula of percentage change. After that,
you will write a program to do the task. In this course, Visual Basic.net the programming
language you use.
To get the idea of how to
create a computer
program, you may refer to
the diagram at the right.
(Note: after having a
finished program, you can
do an evaluation to look
for possible
improvements.)
Define the Problem
Solve the Problem
Write a Program
Testing and Debugging
Evaluation
Chapter 1 Ideas of Programming
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Trivia: The earliest programmers write programs in machine code, because programming languages are not available yet!
1.3 What is a programming language?
In computers, instructions are stored in machine code, that each instruction (e.g. ADD,
SUBTRACT, MULTIPLY, etc.) is given a unique number. Computers can understand machine
code only!
However, machine codes are very difficult to be understood by human. Therefore,
programming languages, that are understandable by human,
are created to bridge the gap.
A programming language consists of a specification and an
implementation. The specification provides a definition of the programming language, and
programmers write programs according to the specification.
And the implementation is a translator: something that converts the program from the
programming language into machine code.
1.4 Compilers
Compilers are a type of translator that converts source code into an object program. The
object program is stored in an executable file (.exe), which can be executed directly in a
computer. The usage of a compiler can be summarized in the diagram below:
Source Code (written in programming
language)
Compiler Object
Program (written in machine code)
Execution
Introduction to Visual Basic - Book 1
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1.5 Names of some programming languages
Here are the names and characteristics of some programming languages. You are only
required to remember the names of these programming languages.
(The characteristics and example are provided for reference only.)
Programming language Characteristics
BASIC
(Beginner’s All-purpose
Symbolic Instruction Code)
BASIC is designed to be easy-to-learn. It gradually evolved
into modern programming languages, firstly QuickBasic, and
then Visual Basic.
Example program Output
10 FOR I=1 TO 5
20 PRINT I*I
30 NEXT I
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Logo Logo is known for drawing attractive graphics. It was used to
teach programming in schools.
Example program Output
REPEAT 5 [FD 100 RT 144]
(Note: FD = forward, RT = right turn.
Only the star is drawn. The triangle is
the cursor, pointing upwards.)
Pascal Pascal was designed mainly to teach good programming
style. Pascal is being taught in the HKDSE ICT syllabus. Some
modern programs are also written in Pascal.
Example program Output
program example1;
var i : integer;
begin
for i := 1 to 5 do
begin
WriteLn(i*i);
end;
end.
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Chapter 1 Ideas of Programming
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Programming language Characteristics
C++ C++ is one of the most popular programming language
(much more popular that Pascal). If you want to be a good
programmer, C++ is a programming language that you must
learn.
C language, the predecessor of C++, is also widely used
today.
Example program Output
#include <iostream>
int main(int argc,char* argv[])
{
for (int i=1; i<=5; i++) {
cout << i*i << endl;
}
}
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Java Java is one of the most popular programming languages,
mostly used in client-server or web applications.
Example program Output
public class HelloWorld{
public static void main(String []args){
for (int i=1; i<=5; i++) {
System.out.println(i*i);
}
}
}
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JavaScript JavaScript is the programming language available in a web
browser, allowing dynamic user interaction in a web site.
New web technologies, i.e. Ajax and HTML5 rely on
JavaScript as the programming language.
PHP PHP is one of the most popular programming languages for
a web server. With PHP you can dynamically generate web
contents, and many other things, depending on user input.
PHP is used in the http://www.tanghin.edu.hk
Visual Basic.net Visual Basic.net is the programming language you are going
to learn in this book. Visual Basic is the easiest programming
language to learn if you want to program in Graphical User
Interface (GUI).
Introduction to Visual Basic - Book 1
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Chapter 2 Visual Basic 2010 Express
2.1 Download Visual Basic 2010 Express
To download Visual Basic 2010 Express, you should search of “Visual Basic 2010” in Google.
After that, click the first link (“Visual Basic 2010 Express | Microsoft Visual Studio”)
(Note: in the PDF version of the file, you can simply click the link above.)
Once you enter the web site, follow the instructions to install the application.
2.2 Register Visual Basic 2010 Express within 30 days
You must register your copy
to use Visual Basic 2010
Express after the 30 days. For
more information, press
“Help” “Register Product”
in the menu bar, and then
follow the instructions (see
the figure) to get a
registration key.
Chapter 2 Visual Basic 2010 Express
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Use only common characters (letters, digits, space, ‘.’ and ‘_’) in the project name. Otherwise, you may not be able to compile your program.
2.3 Your first project
2.3.1 Create and save a new project
The first thing you do in Visual Basic is to start a new project. Follow the instructions
below:
1. Click “New Project”.
2. Choose “Windows
Forms Application”.
3. Give the project a name.
4. Press “Okay”.
Introduction to Visual Basic - Book 1
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Once you have created a project, you should immediately save the project by pressing “Save All”.
In Tang Hin, do not save the project to C drive. When you switch off the computer, everything in C drive will be deleted.
5. Choose “File” “Save
All” in the menu bar.
(Always save the project
first!)
6. Choose a location for
your project.
(The location is only asked
when you press “Save All” for
the first time.)
Chapter 2 Visual Basic 2010 Express
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2.3.2 Introduction to Visual Basic 2010 IDE
After you create and save a project, you can see the screen like the figure below. This is
known as an Integrated Development Environment, or simply IDE. An IDE contains
different kinds of tools that help you to write programs, like source code editor, form
designer, compiler, debugger and many other tools.
If some of the above features is/are missing, you can click the buttons to show them.
(See the figure above for the icons’ position on the screen.)
Toolbox
Solution Explorer
Properties Window
Form Designer
Introduction to Visual Basic - Book 1
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You MUST type all the words, including the punctuations, in exactly the same way. Extra spaces is NOT allowed between letters and digits.
2.3.3 Adding controls and code
Now we add some controls and code to the program. For your first program, follow the
steps below:
1. Find “Button” in Toolbox,
and then put it into the
form.
2. Adjust the size of the form
and the button.
3. Change the property “Text”
of the button to “Go.”
4. Double click the button
“Go”, you should see
that some VB codes
appear.
5. Insert a line of code
shown in the right.
6. Run the program. (Press
the green arrow or F5 in
your keyboard.)
When you run the program, click the button “Go”
(i.e. Button1), and then a message box containing
the message “Hello” will be shown.
Points to note:
The words “Public Class Form1”, “Private Sub …”, “End Sub” and “End Class” must be
put in this order. It is too difficult to understand their meanings at this stage.
The button is known as “Button1” because you can find the words “Button1” in its
“(Name)” property. You can rename the button by setting this property.
Public Class Form1
Private Sub Button1_Click(...) Handles Button1.Click
MsgBox("Hello")
End Sub
End Class
Insert this line of code
Chapter 2 Visual Basic 2010 Express
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2.3.4 Open an existing project
After you save a project, you can open the project later. To open the project, please follow
the instructions here:
1. Click “Open Project”
2. Browse into the folder
and you should see a
“Solution File”. Choose
this file and then click
“Open”.
Alternatively, you can simply use Windows Explorer to find the same Solution File.
However, if you have installed two different versions of Visual Basic, this method may not
work well.
Introduction to Visual Basic - Book 1
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2.4 Structure of a Visual Basic 2010 project
The screenshot below illustrates the folder structure of a Visual Basic project. When you
need to copy the project to another computer, or submit your homework or test in eClass,
remember to ZIP all the contents of the base folder!
Also, when you create a Form in Visual Basic IDE, three files are created. You can open
the .Designer.vb file with a text editor, in order to see the source code. However, no
apparent action can be done in the .resx file.
2.5 Microsoft Developer Network (MSDN)
If you have a question, you can go to Microsoft Developer Network (MSDN) to find the
information. For example, if you want to know the meaning of the keyword “Then”, just
Google “then vb msdn” and you will find the information in MSDN.
The base folder (ZIP all contents of this folder when you need to submit your program to eClass.)
Do not ZIP this one!!!
bin: Find the executable file (.exe) here!
My Project: Configuration and other files
obj: Temporary file created when we compile the program. Safe to delete.
The three files related to “Form1.vb”. Do not delete any of them!
Chapter 3 Working with Controls
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Chapter 3 Working with Controls
3.1 Introduction to GUI programming in Visual Basic
When we create a new program, one of the first things to do is to
create a user interface. The most common type of interface is
called graphical user interface (GUI). You create a GUI program in
Visual Basic by creating a new Windows Form Application.
When you create a new project (see section 2.3.1 for details), you
see an empty dialog box, which is known as a form, and also a
Toolbox with a lot of controls (see the figure).
You can add controls by dragging the controls into the form.
When you finish, press F5 (the function button at the top of the
keyboard) to run the program.
3.2 Controls
In Visual Basic, users interact with the program using the controls
in the form. Each control has its own use. Here are the types of
controls we learn in this chapter:
Type of control Functions
TextBox A text box allows users to enter text (input). It
can also be used to display results (output).
Label
A label provides visual cues to users, e.g.
describe the meaning of the text box next to it.
It can also be used to display results (output).
Button The program performs some actions when the
user press or click the button.
Forms and controls have properties, events, and methods. Together they make the forms
and controls useful for programmers.
Introduction to Visual Basic - Book 1
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Put some controls into a form and change their properties. Don’t forget the form!
3.3 Properties window
You can change the appearance of the controls
(and form) by setting their properties in the
properties window (see the figure).
Here is a shortlist of the properties we use in the course:
Property Use
(Name)
(design time only)*
You give a name to the control, and use this
name to refer to the control in your own
source code.
Text† The text on the control, or the title of the
form.
ForeColor The foreground colour (i.e. colour of the
text) inside the control.
BackColor The background colour (i.e. colour of the
empty space) of the control/form.
Left‡
Top
Horizontal/vertical position of the control,
counted by the number of pixels relative to
the left/top side of its parent.
Width
Height
The width or height of the control, counted
by the number of pixels.
Visible Whether the control is visible to the user.
Enabled Whether users can interact with the control.
If not, the control is usually dimmed.
TextAlign
(design time only)
The horizontal and vertical alignment of the
text inside the control.
Font
(design time only)
The font used by the text in the control.
* Even though we say “design time only”, it is actually possible to change these properties during runtime.
However, how to changing these properties in runtime is too difficult to be included in this course.
† For labels and buttons, there is a subtle difference with the Text property. Search “UseMnemonic” in
Google for details.
‡ In the design view, properties Left and Top are named Location.X and Location.Y instead.
Chapter 3 Working with Controls
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In Visual Basic, the word “Color” is spelt in American English (no “U”).
3.4 Changing properties at runtime
Properties of controls can be changed using the properties window (during design time) or
by Visual Basic code (during runtime).
Here is an example program that changes some
properties of the form and the controls. To enter
the code into Visual Basic IDE, you can double
click Button1 in design view. Can you guess what will happen after Button1 is clicked?
(Note: “Me” refers to the form.)
Example 3.4.1 Changing properties at runtime
Public Class Form1
Private Sub Button1_Click(sender As System.Object, e As
System.EventArgs) Handles Button1.Click
Me.Text = "Button1 Pressed!"
Me.BackColor = Color.Pink
Label1.Text = "Name"
Label1.BackColor = Color.Green
Label1.ForeColor = Color.Yellow
Label1.Top = 80
TextBox1.Text = "Sarah"
TextBox1.BackColor = Color.Red
TextBox1.Enabled = False
TextBox1.Left = 20
Button1.Visible = False
End Sub
End Class
Introduction to Visual Basic - Book 1
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3.5 Assigning values to properties
Different properties accept values of different data types. Please see the table below:
Name of property Data type Example
Text String Me.Text = "Title of the Window"
ForeColor Color* Label1.ForeColor = Color.Red
BackColor Color TextBox1.BackColor = Color.Green
Left Integer Me.Left = 100
Top Integer Label1.Top = 234
Width Integer TextBox1.Width = 300
Height Integer Me.Height = 400
Visible Boolean (True/False) Button1.Visible = True
Enabled Boolean (True/False) TextBox1.Enabled = False
Note: A string is enclosed in a pair of double quotes (""). If you want to have the "
character inside a string, type that character twice. E.g. "She said ""hello"" to
me."
Class Work 3.5
Write down a Visual Basic statement for each of the following operation.
Operation VB statement
Change the background colour of the
TextBox1 to blue.
Make Button2 disappear.
Set the title of the form to
“New Document”
Change the colour of the text in Label1
to yellow.
Move Button1 that Button1 is vertically
aligned with Button2. (Assume that the
heights of both buttons are the same.)
* For a list of the colours available, search for “System.Drawing.Color” in Google.
Chapter 3 Working with Controls
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3.6 Add a comment to your source code
After you write some source code, you should also write some comments in your program.
Comments in Visual Basic start with a single quote ('), which is followed by any text you
want. Please see the following example:
Example 3.6.1 Comments
Public Class Form1
' This is a comment that occupy for a whole line
Private Sub Button1_Click(...) Handles Button1.Click
TextBox1.Text = "Sarah" ' This is another comment
TextBox1.BackColor = Color.Red
End Sub
End Class
It is easy to understand the program if there are only a few lines of source code. However,
after writing 100 or even 1000 lines of source code, it will very difficult to understand the
logic behind the source code without reading the comments.
Exercise 3
1. Write a program with two controls: Button1 and TextBox1.
When Button1 is clicked, the following things should happen:
(a) TextBox1 is disabled,
(b) The background colour of TextBox1 becomes yellow,
(c) Button1 becomes visible, and
(d) The form’s background colour becomes white.
2. Identify the mistakes in the following source code. There is one mistake in each line.
(Note: There are no mistakes with the words Me, Label1, Button1 and TextBox1.)
Me.Title = "Title of the form"
Label1.BackColor = Colour.Green
Button1.Visible = Ture
TextBox1.Enable = False
TextBox1.Text = Very good!
Introduction to Visual Basic - Book 1
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Chapter 4 Events and Methods
4.1 Introduction to events and methods
Besides working with properties, you need to use events and methods to communicate
with the controls.
4.2 Events
When the user does some action in the form (e.g. click a button), an event is raised or
triggered. You can write a procedure in your Visual Basic program to handle the event, and
that procedure will be executed every time the user does the same action.
4.2.1 Introduction to event procedures
In the previous chapters, you have seen something like the following excerpt:
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
[Add your code here]
End Sub
The excerpt above is an event procedure, i.e. a procedure that handles an event. When
Button1 is clicked, the event Button1.Click is handled by the procedure Button1_Click, and
the code inside is executed.
Some Action (e.g. the user clicks a button)
Raise an Event
Execute an Event Procedure
The user clicks Button1
Raise the event Button1.Click
Execute procedure Button1_Click
Chapter 4 Events and Methods
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4.2.2 Adding an event procedure in Visual Basic
Method1 Double click the needed item in a form
A quick method to add an event procedure is to double click the related control in the
form designer. The following events will be created:
Type of control / form Event When the event is raised
Form Load When the form is displayed for the first time
Button Click When the Button is clicked
Label Click When the Label is clicked
TextBox TextChanged When the Text property of the TextBox is changed
Method2 Select the event in the source code window
If you want to create other event procedures, then you need to select the list in the source
code view. First, select the control at the left, and then select the event at the right.
Note: To add events to Form1, select “(Form1 Events)” instead of “Form1”.
Introduction to Visual Basic - Book 1
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4.2.3 Names and types of events
The most commonly used events of are Load and Click. Here is a shortlist of events we use
in this course:
Name of event When the event is raised
Load Before a form is displayed the first time. In most cases, this is when
the program starts running.
Click When the user clicks a form or control (e.g. Button).
DoubleClick* When the user double clicks certain kinds of controls (e.g. Form,
Label, TextBox). Note: A Button does not raise the DoubleClick event.
TextChanged† When the content of the Text property is changed (either by user
input or by Visual Basic.net code.)
MouseEnter When the mouse enter a form or control
MouseLeave When the mouse leaves a form or control
We identify an event by connecting the name of the control and the name of the event
using a dot symbol, e.g. Button1.Click, TextBox2.TextChanged, etc.
Events related to the form are prefixed by “Me” or “MyBase”, e.g. MyBase.Load‡,
Me.Click, Me.MouseEnter, etc.
Class Work 4.2.3
Identify the events raised by the actions below:
Action Event raised
Execute a program
Click Button1
The text inside TextBox1 is changed
The mouse cursor leaves Label3
* Only some types of controls raises DoubleClick events. For details, see
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.doubleclick.aspx
† TextChanged events are also raised when the form is created, before the Load event is raised. Open
Form1.designer.vb in a text editor to see the reason behind. Careless implementation of TextChanged events
causes runtime errors.
‡ It is okay to use either Me.Load or MyBase.Load
Chapter 4 Events and Methods
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4.2.4 The structure of an event procedure
You can look at the following example for the structure of an event procedure.
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
[Add your code here]
End Sub
Now the code is explained part by part:
Part Meaning
Private Sub Declare a procedure
Button1_Click The name of the procedure. The default is the name of the
event, with “.” changed to “_”. You can change this name by
yourself.
(sender As System.Object,
e As System.EventArgs)
Currently unimportant. Usually abbreviated as (…) in this
book
Handles Button1.Click The event or events to handle. Change this to something like
“Handles Button1.Click, Button2.Click, Button3.Click”
to handle multiple events in the same procedure
End Sub Marks the end of the event procedure
4.2.5 TextChanged events
A correct implementation of TextChanged events is provided here without explanation.
You should read this section again after you finish Chapter 7.
Public Class Form1
Dim loaded As Boolean = False
Private Sub Form1_Load(...) Handles MyBase.Load
loaded = True
End Sub
Private Sub TextBox1_TextChanged(...) Handles TextBox1.TextChanged
If Not loaded Then Exit Sub
' Add your code below
End Sub
Private Sub TextBox2_TextChanged(...) Handles TextBox2.TextChanged
If Not loaded Then Exit Sub
' Add your code below
End Sub
End Class
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Introduction to Visual Basic - Book 1
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4.3 Methods
A method is a procedure that exists inside the control. You invoke methods to do
something with a control. Sometimes it is possible to the same thing using either
properties or methods. For example, the statements “Form2.Visible = True”
(setting a property) and “Form2.Show()” (invoke a method) do the same thing.
Here is the list of methods we learn in the course:
Control Method Meaning Example
[All] Hide Hide a control/form. Form2.Hide()
[All] Show Show a control/form. Form2.Show()
Form ShowDialog Show a form as a modal dialog box.
(A modal form must be closed or hidden before you can
continue working with the rest of the application.)
Form2.ShowDialog()
Form Close Close a form. The program ends when
the startup form (usually Form1) is
closed.
Me.Close()
TextBox AppendText Add some text to the end of the
current text in the text box.
TextBox1.AppendText("Hello")
TextBox Paste Paste some text to the
cursor/selection of the text box.
TextBox1.Paste("Hello")
Example 4.3.1 AppendText and Paste methods Public Class Form1
Private Sub ButtonAppendText_Click(...) Handles ButtonAppendText.Click
TextBox2.AppendText(TextBox1.Text)
End Sub
Private Sub ButtonPaste_Click(...) Handles ButtonPaste.Click
TextBox2.Paste(TextBox1.Text)
End Sub
End Class
Note: When you run the example, you should note
the way computer join strings. No extra spaces are
added by the computer!
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Chapter 4 Events and Methods
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A hidden form is NOT closed. If the startup form is hidden, then the program may not end properly! (If it happens, you can terminate the program in the Task Manager.)
Example 4.3.2 Multiple forms (try the buttons and text box yourself)
Form1.vb Public Class Form1
Private Sub ButtonShow_Click(...) Handles ButtonShow.Click
Form2.Show()
End Sub
Private Sub ButtonShowDialog_Click(...) Handles ButtonShowDialog.Click
' Note: a runtime error will occur if Form2 is already visible
Form2.ShowDialog()
End Sub
End Class
Form2.vb Public Class Form2
Private Sub ButtonClose_Click(...) Handles ButtonClose.Click
Me.Close()
End Sub
End Class
Class Work 4.3
Write down Visual Basic statements for each of the following operation.
Operation VB statement(s)
Append “Hello!” to TextBox1.
Show Form3 as a modal dialog box.
Show Form2 as a modal dialog box. The
current form is hidden until Form2 is
closed.
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Introduction to Visual Basic - Book 1
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Make sure your source code is inputted in the correct events! Check for spelling mistakes!
Exercise 4
1. Write a program with two controls: Button1 and Button2.
When Button1 is clicked, the following things should happen:
(a) Button1 is disabled,
(b) The text in Button1 becomes
“Disabled!!!”,
(c) Button2 becomes visible, and
(d) The form’s background colour becomes pink.
And when Button2 is clicked, the following things should happen:
(a) Button1 is enabled,
(b) The text in Button1 goes back to “Button1”,
(c) Button2 becomes invisible, and
(d) The form’s background colour becomes yellow.
2. Write a program to tease the user with a button labelled “Click Me”. In this program,
the user cannot press a button because the following happens:
When the mouse is inside the form, the button is disabled. When the mouse is
outside the form, the button is enabled again. To verify that the tease works, you
should also add a Click event for the button, which changes the text of the button to
“Clicked”.
(Note: I would like to replace the words “form” by “button” in the question, but the
program created that way does not work properly. Also, is there any way to raise the
Click event even when the program is correctly implemented?)
Chapter 5 Variables, Input and Output
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Chapter 5 Variables, Input and Output
5.1 Variables
In Visual Basic, you use variables to store values. Variables have a name and a data type.
5.1.1 Declaring variables with Dim statement
Before you use a variable, you should tell Visual Basic in advance, using the Dim statement:
Dim variablename [As type]
The data type of the variable can be one of the following:
Data type Description
Integer Integer (between -2,147,483,648 through 2,147,483,647)
Single Single-precision floating-point (about 7 significant figures).
Double Double-precision floating-point (about 16 significant figures).
Boolean True or False
String Text (holds your name, ID card number, etc…)
Example 5.1.1 Dim statements
Dim score As Integer
Dim weight As Double
Dim finished As Boolean
Dim name As String
Class Work 5.1.1
Determine the correct data type(s) for the following data, and write down a Dim
statement, where the name of the variable is the underlined word.
Description of data Data type Dim statement
The height of a student (in cm).
The marks of a test.
The academic grade of a student.
The age of your father.
Whether you are wealthy.
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Visual Basic is not case sensitive,
e.g. ScOrE and score are the same name in Visual Basic .
5.1.2 Keywords and names of variables
Some words have special meanings in Visual Basic, such as Dim, As, Integer, Double,
Boolean, and String. These words are known as keywords, or reserved keywords. The
list of keywords in Visual Basic 2010 can be found in
http://msdn.microsoft.com/en-us/library/dd409611(VS.100).aspx
The name of a variable cannot be any of the
reserved keywords. In addition, it must obey the
following rules:
It must begin with an alphabetic character or an underscore (_).
It must only contain alphabetic characters, decimal digits, and underscores.
It must contain at least one alphabetic character or decimal digit.
It must not be more than 1023 characters long.
5.1.3 Giving values to variables in the Dim statement
We can assign a value to a variable in the same Dim statement. This is a good practice in
programming because it eliminates potential mistakes.
Example 5.1.2 Dim statements with initial values
Dim score As Integer = 0
Dim weight As Double = 129.3
Dim finished As Boolean = False
Dim name As String = "Chan Tai Man"
5.1.4 Declaring several variables in a single line
We can declare several variables in a single Dim statement. However, in Visual Basic, we
cannot assign a value to these variables at the same time.
Example 5.1.3 Dim statements with several variables in one line
Dim a, b, c As Single, x, y As Double, i As Integer
' a, b, and c are all Single; x and y are both Double
Chapter 5 Variables, Input and Output
29
5.1.5 Using variables to store values
We can assign a value to a variable with the equal sign “=”. Once a new value is stored in
the variable, the old value is forgotten. See the example below:
Example 5.1.4 Use of variables
Dim x, y As Integer
x = 5 ' x is set to 5
y = 3 ' y is set to 3
x = 2 ' x becomes, y is unchanged
y = x + 2 ' y becomes (x+2)=(2+2)=4, x is unchanged
x = y + 3 ' x becomes (y+3)=(4+3)=7, y is unchanged
Class Work 5.1.2
With reference to the programs below, write down the values of the variables after the
execution of each of the statements.
Program Value of a Value of b Value of t
Dim t As Integer
Dim a As Integer = 2 2
Dim b As Integer = 6 2 6
t = a
a = b
b = t
Program Value of p Value of q
Dim p As Double = 3
Dim q As Double = 4.5
q = p - 0.5
p = 2
p = (p + q) / 2
q = (p - q) / 2
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5.1.6 Scope of variables
The variable can be declared inside the Class or inside a Sub procedure. The variable is
only effective inside the Class or Sub structure. Once the given structure finishes
execution, the variable is deleted and its value is forgotten. Here is an example:
Variable
inside Class
Public Class Form1
Dim x As Integer = 20
Private Sub Button1_Click(...) Handles Button1.Click
x = x + 10 'increase x by 10
Label1.Text = x
End Sub
End Class
After execution of Sub Button1_Click,
the new value of x is remembered.
Therefore, x is increased by 10 every time we click the button.
Variable
inside Sub
Public Class Form1
Private Sub Button1_Click(...) Handles Button1.Click
Dim x As Integer = 20
x = x + 10 'increase x by 10
Label1.Text = x
End Sub
End Class
After execution of Sub Button1_Click,
the new value of x is forgotten
because x is declared inside Sub Button1_Click.
Therefore, x becomes 20 + 10 = 30 every time we click the button.
If a variable exists both inside and outside the sub, the variable inside the sub is used.
You may also declare variable inside an If…Then…Else statement (see chapter 7) or other
statement blocks. Like the case with Sub procedure, those variables will be forgotten after
the statement block finish execution.
Chapter 5 Variables, Input and Output
31
Class Work 5.1.3
The following is a program with label Label1 and buttons Button1, Button2 and Button3.
Public Class Form1
Dim x As Integer = 5
Private Sub Button1_Click(...) Handles Button1.Click
Dim x As Integer
x = 8
Label1.Text = x
End Sub
Private Sub Button2_Click(...) Handles Button2.Click
Label1.Text = x
End Sub
Private Sub Button3_Click(...) Handles Button3.Click
x = 12
Label1.Text = x
End Sub
End Class
Now the program is run and the buttons is pressed step by step as follows. Determine the
value of Label1.Text after each step:
Step Action Value of Label1.Text
1 Run the program.
2 Click Button1.
3 Click Button2.
4 Click Button3.
5 Click Button1.
6 Click Button2.
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Without the Val function, a runtime error occurs if the user press “Cancel” in the InputBox.
5.2 Introduction to InputBox and MsgBox
Besides using labels and textboxes, we can use InputBox and MsgBox to handle input and
output. In this part, we only deal with the simplest way to handle input and output. The
details will be discussed in the second term.
5.2.1 InputBox
To use an InputBox to input a string, we use the following statement:
variablename = InputBox("message")
If you want to input a number, you should use
the Val function to convert the string into a
number, i.e.
variablename = Val(InputBox("message"))
Here is an example asking for your name using InputBox:*
Example 5.2.1 InputBox
Dim s As String
s = InputBox("What is your name?")
* Starting from this chapter, there may be no Button1 and Button1.Click in the examples. You should create
the button Button1 and the event Button1.Click yourself, and then input the code inside Button1.Click.
Chapter 5 Variables, Input and Output
33
If you want to check the value of a variable, you can add a MsgBox statement in your source code..
5.2.2 MsgBox
To use MsgBox to display a message, we use the following statement:
MsgBox("message")
Here is an example using MsgBox:
Example 5.2.2 MsgBox
MsgBox("This is a wonderful message!")
If you want to display a message with more than one line, see the example below. The “&”
character join strings together, and vbCrLf is similar to the “Enter” key in the text editor.
(Note: the example below should be typed in a single line.)
Example 5.2.3 Multiline MsgBox
MsgBox("You Won!!!" & vbCrLf & vbCrLf & "You rolled a 6"
& vbCrLf & "and the computer rolled a 5!")
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5.2.3 Miscellaneous examples
Example 5.2.4 Calculate the product of two numbers
Dim x, y, product As Double
x = Val(InputBox("Input the first number."))
y = Val(InputBox("Input the second number."))
product = x * y
MsgBox("Their product is: " & product)
Exercise 5
1. Rewrite Example 5.2.4 into a program that uses text boxes and labels but not
InputBox and MsgBox.
2. Write a program that uses InputBox to input two numbers when the form is loaded.
The numbers are stored into two variables. Now the user can press one of the four
buttons, that each of the buttons does a basic arithmetic operation (i.e. +, –, × or ÷)*
on the two numbers, and then display the results using an MsgBox.
Note: Do not use any text boxes or labels in this question.
3. Suggest a name and a data type of the variable for each of the following.
Meaning of variable Name of variable Data type
The class of a student.
The date of the computer examination.
* The “×” symbol can be typed by pressing Alt+0215. It means holding the Alt key and typing 0215 in the
numeric keypad while the Alt key is held. Similarly, “÷” can by typed by pressing Alt-0247.
Chapter 6 Operators and Expressions
35
Chapter 6 Operators and Expressions
You can enter expressions in Visual Basic to do calculations. The expressions in Visual Basic
are similar to what you type in your calculator, Casio fx-50FH.
Operators in Visual Basic can be classified into arithmetic operators, (string) concatenation
operators, relational operators and logical operators. The first two types are discussed in
this chapter, while the others are discussed in the next chapter.
6.1 Arithmetic Operators
Here is a list of the arithmetic operators in Visual Basic 2010. You should get yourself
familiar with the operators “\” and “Mod” before examinations.
Operator Meaning Example Result
+ Addition 3+8 11
- Subtraction 10-15 -5
-(unary) Negation -2 -2
* Multiplication 3*8 24
/ Division (floating point) 14/4 3.5
\ Integer division
Note: Avoid decimals. They are rounded off in a strange way.
14\4
31.25\4.5
3
7
Mod Find the remainder of division
(decimals are okay)
10 Mod 4
31.25 Mod 4.5
-5 Mod 2
2
4.25
-1
^ Exponentiation 3^4 81
Class Work 6.1
Evaluate the following expressions:
VB expression Result VB expression Result
3 + 6 3 * 6
3 - 6 2 ^ 5
15 / 7 5 ^ 2
15 \ 6 3 ^ (5 - 2)
15 Mod 6 3 + 4 * 5
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Do not forget to add a pair of
parentheses. E.g. 𝑎
𝑏+𝑐 should be
“a/(b+c)” but not “a/b+c”.
Adding a number and a string by
the “+” sign, e.g., "4" + 2 , will produce a runtime error!
6.2 Parentheses (singular: parenthesis)
Parentheses (or brackets) are used to force some
parts of an expression to be evaluated before
others.
Class Work 6.2
Convert the following expressions into Visual Basic code:
Mathematical expression VB statement
a = b + c
(
)
6.3 Concatenation Operators
Concatenation is the operation joining two strings together. The strings are simply joined
together into a single string. There are two concatenation operators in Visual Basic: “+”
and “&”. The “&” operators is preferred because it is defined for strings only.
Example: "Con" & "caten" & "ation"
evaluates to "concatenation"
Note: No space is added to the strings.
Chapter 6 Operators and Expressions
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6.4 Operator Precedence
Similar to Mathematics expressions, the evaluation of expressions in Visual Basic is
ordered by its operator precedence (also called order of operations). Here is the list*:
(Note: operators that are introduced in later chapters are also listed here.)
Low
est ←
− −
− −
− −
− −
→ H
igh
est 11 Exponentiation ^
10 Unary identity and negation† + –
9 Multiplication and floating-point division * /
8 Integer division \
7 Modulus arithmetic Mod
6 Addition and subtraction + –
5 String concatenation &
4 Relational/comparison operators = <> < <= > >=
3 Negation Not
2 Conjunction And
1 Inclusive disjunction Or
For operators in the same order of precedence, the calculations are done left-to-right.
Class Work 6.4
Evaluate the following expressions:
VB expression Result
"con" & "cent" & "rated"
4 * 3 & 5 * 2
9 - 25 / 2 * 3
9 - 25 \ 2 * 3
-35 Mod 3 ^ 3
* The operator precedence table above is only valid of Visual Basic. It is different for Excel.
† A unary operator has only one expression next to it. e.g. the – sign in – .
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6.5 Increment and Decrement
One of the most common operations in a program is to increase and decrease the value of
a variable. See the following example for an idea.
' Assigns the value 10 to the variable.
applesSold = 10
' The following statement increments the variable.
applesSold = applesSold + 1
' The variable now holds the value 11.
In the previous example, the statement applesSold = applesSold + 1 increase the
value of the variable applesSold by 1. You may also write applesSold += 1 instead.
In the example, += is an assignment operator, which add a certain value to a variable.
-=, *=, /=, \=, ^= and &= are having similar meanings.
Class Work 6.5
Express the following actions into Visual Basic code:
Action VB statement
Increase x by 100
Decrease y by 5
Multiple product by -3
Add "sugar" to the end of the str1
Move the form downwards by 3 pixels
Move the form to the left by 20 pixels
6.6 Val function
In Chapter 5, you have learnt to use the Val function to convert strings into numbers. We
use the Val function in either of the following ways:
variablename = Val(InputBox("message"))
variablename = Val(TextBox1.Text)
We call Val a function because it returns a value that can be assigned to a variable.
Similarly, InputBox is also a function.
Chapter 6 Operators and Expressions
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6.7 Mathematical Constants and Functions
Here is a list of mathematical functions you will use in Visual Basic:
Function Meaning Example Result
Math.Sqrt Find the square root of a number. Math.Sqrt(4) 2
Int
(or Math.Floor)
Round down to the nearest integer. Int(2.3)
Int(-2.3)
2
-3
Math.Max Returns the larger of two numbers. Math.Max(2, 5) 5
Math.Min Returns the smaller of two numbers. Math.Min(2, 5) 2
Math.Abs Absolute value (remove the negative
sign).
Math.Abs(-4) 4
Math.Sign The sign of the number.
1 = positive, 0 = zero, -1 = negative
Math.Sign(-5) -1
Fix
(or Math.Truncate)
Find the integral part of a number. Fix(2.3)
Fix(-2.3)
2
-2
Math.Ceiling Round up to the nearest integer. Math.Ceiling(2.3)
Math.Ceiling(-2.3)
3
-2
Math.Round Round off a number to an integer or a specified number of decimal places. (Note: The behavior of this function is a bit different from what you learn in Mathematics. See MSDN for details.)
Math.Round(12.56)
Math.Round(12.56,1)
13
12.6
And here is a mathematical constant in Visual Basic:
Constant Meaning Example Result
Math.PI The value of . Math.PI 3.141592653589793
Class Work 6.7
Convert the following expressions into Visual Basic code:
Mathematical expression VB statement
√
( √ )
√ √
En
rich
men
t
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6.8 Miscellaneous Examples
Example 6.8.1 Find the value of a polynomial
Public Class Form1
Private Sub Button1_Click(...) Handles Button1.Click
Dim x As Double = Val(TextBox1.Text)
LabelResult.Text = -x ^ 2 + x + 3
End Sub
End Class
Example 6.8.2 Cycling through 0 to 9
Public Class Form1
Private Sub Button1_Click(...) Handles Button1.Click
Dim n As Integer = Val(Label1.Text)
Label1.Text = (n + 1) Mod 10
End Sub
End Class
Example 6.8.3 Marks Counter
Public Class Form1
Private Sub ButtonPlus20_Click(...) Handles ButtonPlus20.Click
Dim marks As Integer = Val(LabelMark.Text)
marks = marks + 20
LabelMark.Text = marks
End Sub
Private Sub ButtonMinus10_Click(...) Handles
ButtonMinus10.Click
Dim marks As Integer = Val(LabelMark.Text)
marks = marks - 10
LabelMark.Text = marks
End Sub
End Class
LabelResult
TextBox1 Button1
Button1
Label1
LabelMarks
ButtonPlus20
ButtonMinus10
Chapter 6 Operators and Expressions
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Exercise 6
1. Write a program to find the value of the n-th triangle number, i.e. .
2. Write a program to calculate the value of in .
3. Rewrite the programs in the previous questions, using InputBox for input and MsgBox
for output.
4. Write a program similar to Example 6.8.2. However, the number in the box should
cycle backwards, i.e. 0, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 9, …
5. Write a program that calculates percentage changes. The program should be able to
find the original value, the new value and the percentage change.
(Hint: What are the formulas?)
6. Write a program with four buttons: up, down, left and right. When you press the
button, the form moves itself by 10 pixels, to the direction indicated by the button.
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Chapter 7 Flow Control (1)
7.1 Decision Making
A logical expression can give Boolean results, i.e. True or False. A computer can use these
results to make decisions.
7.2 Relational Operators
Relational operators (or comparison operators) are the equality signs and inequality signs
in Mathematics. If the equality or the inequality is satisfied, then the result is True,
otherwise the result is False. Here is the list of the relational operators:
Operator Meaning Example Result Opposite
= Equal to 9 = 11
> Greater than 11 > 9
< Less than 11 < 9
>= Greater than or equal to 15 >= 15
<= Less than or equal to 9 <= 15
<> Not equal to 9 <> 9
Class Work 7.2
Convert the following comparison into Visual Basic code:
Comparison VB code
1. Is Peter (PHeight) taller than Mary (MHeight?)
2. Is Linda’s age (LAge) not equal to May’s age (MAge)?
3. The passing mark is 50. Has Gigi (GMark) failed the test?
4. It is free to travel by MTR for a person with height 100 cm
or below. Is it free for Kitty (KHeight) to travel by MTR?
5. Is X an even number?
Chapter 7 Flow Control (1)
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7.3 If...Then...Else Statement
The If...Then...Else statement conditionally executes a group of statements, depending on
the value of an expression. (See the flowchart below.)
The basic If…Then…Else syntax is listed here.
If condition Then
Statement1
Statement2
...
Else
Statement3
Statement4
...
End If
Sometimes we do not want to execute anything if the condition is false. In this case, we
can skip the keyword Else, i.e.
If condition Then
Statement1
Statement2
...
End If
Introduction to Visual Basic - Book 1
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marks>=50?
result="Pass"result="Fail"
start
input marks
end
output result
Yes
No
The spelling of the word ElseIf is
E-L-S-E-I-F, not E-L-S-E-L-F!
The following example shows the use of If...Then...Else statements:
Example 7.3.1 Pass or failure
Dim marks As Integer
Dim result As String
marks = Val(InputBox("Enter the marks:"))
If marks >= 50 Then
result = "Pass"
Else
result = "Fail"
End If
MsgBox(result)
In the above example, if the marks is more than or equal to 50,
then the result is “Pass”. Otherwise (i.e. marks less than 50),
the result is “Fail”.
7.4 Multiple conditions with keyword ElseIf
If you want to have more than two outcomes, you can add additional conditions using the
keyword ElseIf (else and if together in one word).
If condition1 Then
Statement1
...
ElseIf condition2 Then
Statement2
...
(more ElseIf conditionals if applicable)
Else
Statement3
...
End If
Chapter 7 Flow Control (1)
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marks>=80?
start
end
input marks
marks>=70?
output grade
marks>=50?
grade = "A"
grade = "B"
grade = "C"
grade = "D"
No
No
Yes
Yes
Yes
No
To see how the keyword ElseIf works, see the example below:
Example 7.4.1 Grading the results
Dim marks As Integer
Dim grade As String
marks = Val(InputBox("Enter the marks:"))
If marks >= 80 Then
grade = "A"
ElseIf marks >= 70 Then
grade = "B"
ElseIf marks >= 50 Then
grade = "C"
Else
grade = "D"
End If
MsgBox("Your grade is: " & grade)
In this example, the marks are used to determine
the grade. When we check for the second
condition marks >= 70, we already know that
marks >= 80 is false. Therefore, only people
with marks from 70 to 79 get a grade of “B”.
(Note: In this example, the marks are integers.
This is NOT true in Tang Hin, where the marks are correct to 2 decimal places.)
Class Work
With reference to Example 7.4.1, please fill in the table below:
Marks Grade
≥ 80 “A”
“B”
“C”
“D”
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7.5 Official Syntax of If...Then...Else Statement
Here is the official syntax of the If…Then…Else statement. The parts inside [] are optional.
If condition [ Then ]
[ statements ]
[ ElseIf elseifcondition [ Then ]
[ elseifstatements ] ]
[ Else
[ elsestatements ] ]
End If
-or-
If condition Then [ statements ] [ Else [ elsestatements ] ]
When you enter your code into the Visual Basic IDE, it will do the following changes
automatically:
Add the missing keyword “Then”
Change “Else If” into “ElseIf”
Change “EndIf” into “End If”
And here is an example of the single line syntax. The symbol “:” is used to separate
multiple statements. (Note: you may use “:” outside the If…Then…Else statement.)
If A > 10 Then A = A + 1 : B = B + A : C = C + B
Chapter 7 Flow Control (1)
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Exercise 7
1. Write a program that the user will enter the number . If , output
“A big number!” in a label, otherwise output “A small number!”.
2. Write a program that the user will enter the amount of pocket money he/she spends
per week. Then the program will output a message according to the table below:
Pocket Money ($) Message
0 You didn't spend any money. Are you lying?
>0 and <$100 Below average. What a good student!
>=$100 and <$200 Average.
>=$200 Above average. Consider to spend less!
3. BMI Calculator: The Body Mass Index (BMI) is a method to see if you are overweight
or underweight. Your program should receive two inputs: mass (in kg) and height (in
cm). Calculate the BMI by to the formula
. (Be careful with the
unit!!!)
Finally, your program should determine the result according to the following table:
BMI Classification
<18.5 Underweight
18.5 – 23.9 Average
24.0 – 27.9 Overweight
>= 28 Obese
(Note: what should be classification if BMI = 23.91?)
4. Write a program that the user will enter his/her marks in Chinese, English and
Mathematics subjects. Then output the number of subjects that he/she has failed (i.e.
marks less than 50).
Introduction to Visual Basic - Book 1
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Alphabetical Index
A AppendText (method)............... 24
As (keyword) ............................. 27
B BackColor (property)................. 16
Boolean (data type) .................. 27
Button (control) ........................ 15
C Class (keyword) ......................... 30
Click (event) .............................. 22
Close (method) ......................... 24
code .......................................... 12
comment................................... 19
compiler ...................................... 5
concatenation ........................... 36
control ................................ 12, 15
D data type ............................. 18, 27
design time ............................... 17
Dim (statement) ........................ 27
Double (data type) .................... 27
DoubleClick (event) ................... 22
E Else (keyword) .......................... 43
ElseIf (keyword) ........................ 44
Enabled (property) .................... 16
event ......................................... 20
event procedure ....................... 20
F False (keyword) ......................... 27
Font (property) ......................... 16
ForeColor (property) ................. 16
form .......................................... 15
form designer ........................... 11
G graphical user interface ............ 15
GUI .... See graphical user interface
H Height (property) ...................... 16
Hide (method) ........................... 24
I IDE ... See Integrated Development
Environment
If (keyword) ............................... 43
If...Then...Else (statement) ........ 43
InputBox .................................... 32
Integer (data type) .................... 27
Integrated Development
Environment ........................ 11
K keyword .................................... 28
L Label (control) ........................... 15
Left (property) ........................... 16
Load (event) .............................. 22
M machine code .............................. 5
mathematical functions ............ 39
Me (keyword)...................... 17, 22
method ..................................... 24
Microsoft Developer Network .. 14
Mod (operator) ......................... 35
MouseEnter (event) .................. 22
MouseLeave (event) ................. 22
MSDN ..... See Microsoft Developer
Network
MsgBox ..................................... 33
MyBase (keyword) .................... 22
N Name (property) ....................... 16
New Project ................................ 9
O object program ........................... 5
Open Project ............................. 13
operator precedence ................ 37
operators .................................. 35
arithmetic operators ............ 35
assignment operators .......... 38
concatenation operators ..... 36
relational operators ............. 42
P parentheses .............................. 36
Paste (method) ......................... 24
procedure ................................. 20
program ...................................... 4
programming .............................. 4
programming language ............... 5
BASIC ..................................... 6
C++ ......................................... 7
implementation ..................... 5
JavaScript ............................... 7
Logo ....................................... 6
Pascal ..................................... 6
PHP ........................................ 7
specification ........................... 5
Visual Basic.net ...................... 7
Properties Window ................... 11
property .................................... 16
R reserved keywords .................... 28
runtime ..................................... 17
S Save All ...................................... 10
scope of variables ..................... 30
Show (method) ......................... 24
ShowDialog (method) ............... 24
Single (data type) ...................... 27
Solution Explorer ....................... 11
source code ........................... 5, 12
String (data type) ...................... 27
Sub (keyword) ........................... 30
T Text (property) .......................... 16
TextAlign (property) .................. 16
TextChanged (event) ........... 22, 23
Then (keyword) ......................... 43
Toolbox ..................................... 11
Top (property) ........................... 16
translator .................................... 5
True (keyword) .......................... 27
U user interface ............................ 15
V Val (function) ...................... 32, 38
variable ..................................... 27
vbCrLf (constant) ....................... 33
Visible (property) ...................... 16
Visual Basic 2010 Express ............ 8
W Width (property) ....................... 16
Windows Form Application ... 9, 15