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What is Visual Basic?
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Microsoft Visual Basic Tutorial |
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Visual Basic also known as VB is a programming
language from Microsoft. It is part of the Microsoft
Visual studio software package. Using Visual Basic
you can develop Windows and Web applications. Visual
Basic is an Object Oriented Programming with full
capabilities and concepts like objects, properties,
classes, events, methods, inheritance and encapsulation.
In addition to Visual Basic, Microsoft Visual Studio
includes Visual c# (C sharp), Visual C +, Visual F+ and
a few other titles. If you look for our
old content on Visual Basic, please visit VB 6.0 page.
If you want to
download a trial version of Microsoft Visual Studio,
please visit the following Visual
Studio 2010 site:
http://www.microsoft.com/visualstudio/en-us/try
History of Visual Basic with timelineVisual
Basic was derived from BASIC , an
introductory computer language for non techies. Visual
Basic is a third generation OOED (object oriented, even
driven) language. Here is the time line on Visual Basic
versions:
Date of Release |
Version |
Significant
Milestones |
March 1991 |
Visual Basic 1.0 |
Create Windows applications
quickly
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November 1992 |
Visual Basic 2.0 |
Support for ODBC and MDI forms |
October 1996 |
Visual Basic 4.0 |
Create 32 bit as well as 16-bit Windows
application |
October 1998 |
Visual Basic 6.0 |
Active X controls and Database
Access |
February 2002 |
Visual Basic .Net (VB 7.0) |
Major Shift to NET framework and also
focused on XML based application |
October 2005 |
Visual Basic .Net 2005 (VB 8.0) |
Support for .NET 2.0 and partial
classes |
November 2007 |
Visual Basic .Net 2008 (VB 9.0) |
Support for .NET 3.5 and LINQ |
November 2010 |
Visual Basic .Net 2010 |
Added features like Inline functions |
1996 |
VBScript (Active Scripting) |
Used for Web and Administration
applications |
1993 |
VBA (Visual Basic for Applications) |
Used for programming in MS Office
applications |
How do I learn Visual Basic?In our opinion, the
best way to learn Visual Basic is with Hands-on
examples. In today’s tutorial on Visual Basic, we will
use Microsoft Visual Basic 2010 Express
. You can download a FREE version from
this location.
http://www.microsoft.com/visualstudio/en-us/products/2010-editions/visual-basic-express
We
will guide you through the basic steps of how to create
a simple login Visual Basic application. In order to get
started, after you download and install the VB software,
you can launch the program by following
this:
All Programs > Microsoft Visual
Studio 2010 Express > Microsoft Visual Basic 2010
Express.
You will get a new window
similar to the one shown below. Here you can choose what
type of Visual Basic project you will create. We select
Windows Form Application, type LoginScreen for the Name
and click OK.
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Microsoft Visual Basic 2010 interface:If you do
the same thing as above and click OK, you should see the
VB GUI (Graphic User Interface). It is also known as
Visual Basic IDE (Integrated Development Environment).
This is where you have all the necessary tools and
commands that will help you build the
application.
We have included a screen capture
shown below:
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Before we get going with our example on Visual
Basic 2010, we are going to cover basic VB GUI
windows.
File Menu:
Highlighted in aquamarine, you can use this to create,
debug, add components and save a VB project
Toolbar: Right below the File
Menu, you will see icon for commonly used functions like
Copy, Paste, Save, Inserting comments, Debugging (green
play button) and other debugging
options.
Toolbox: This is on the
left side of the IDE and enclosed in red color. This is
the container of all different object controls and
objects like text boxes, labels, command buttons and
others available in VB.
Form/Code
window: Highlighted in blue and nested in the
middle, you can see the VB Form. This is where you can
add the controls we mentioned in the Toolbox onto the
Form
Solution Explorer:
Highlighted in green, here you have all the project
information including VB forms, references and other
project related
items
Properties: Highlighted in
purple, this is where you can review properties of form
controls. You can also change objects properties
anything from size to dimensions to color.
How to create a Visual Basic application?The
best way to learn anything is by getting your hands
dirty and practicing with it. We are going to do just
here with a new Visual Basic application. We will be
developing a simple project that can be used as a login
screen. We will need a form with textboxes for username
and password entry. The program should then check the
credentials and give out a message for either approved
access or denial.
First we are going to add some
VB controls. We begin by adding a Panel object to our
form Form1. In order to do this, you can drag the Panel
(light orange) from Visual Basic Toolbox window and drag
it onto the Form in the middle. Notice
Location and Size
values in the Properties window on the right side.
Here is what it looks like on our monitor
screen:
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Next we are going to add the following Visual
Basic controls:
VB Control
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Object Name |
Label |
lblUserName |
Label |
lblPassword |
TextBox |
txtUserName |
TextBox |
txtPassword |
Button Control |
cmdLogin |
Button Control |
cmdCancel |
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We have highlighted the VB Controls in the
Toolbox window below (purple) and actual txtPassword
control on form Form1 (blue). When we did that, it shows
the property of this text box in properties window
(red).
Here is what our screen in Visual
Basic looks like:
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How will the Login VB application function?Here
is how the program will function:
First the user
will enter their username and password information. When
they click on the Login button control, the VB program
then needs to check the username and password
credentials. If a match is found, a welcome message is
displayed otherwise we will politely tell them to leave
the premises!
In order to write the code behind a
VB control, you simply double click on the control. In
this case, the control is the Login command button, so
we double click on it. This will launch the Code window
also known as Code editor. We have included a screen
shot here, notice now we have two
tabs:
Form1.vb - VB Code
window
Form1.vb [design] -
Actual Visual Basic form
Right below
these tabs, we have highlighted two important
things:
btnLogin -
highlighted in blue, this is the VB object we are going
to program for
Click -
highlighted in green, this is the object event we are
going to program for
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Ready to enter some VB Code?Next we are ready
to start the VB statements. Go ahead and enter the
following code:
'Enter code
here
'if then logic to check
condition
If
txtUserName.Text = "learningcomputer"
And
txtPassword.Text = "Passw0rd1"
Then
'Access
granted'
MsgBox( "Welcome to Visual Basic
2010")
Else
'Access
denied'
MsgBox( "Please leave the
premises")
Me.Close()
End
If
The lines that start with an
apostrophe ' are comments (highlighted in green). These
help the programmer understand the function of the code
that follows the comment. Here is what the Visual Basic
program code looks like on our
screen:
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Before we explain this programming code,
let’s cover the basic of conditional logic in
VB.
Conditional logic in Visual Basic:When the
program is being executed, the VB code will have to make
decisions depending on the input. We do this by using
conditional logic in the programming code. There are two
ways to check for conditions in Visual Basic. Here are
the methods:
1. Select case
statement
More information on this can
be found on this excellent VB site
2. If-then
statement
If-then is the most common
method for decision making in Visual Basic. Here’s
the basic syntax of if-then statement:
If
condition= true then
execute true
statements
else
execute false state
ments
end if
Notice it is common to
indent (tab) the statements after the if clause and else
clause. So for our example, let’s check out the first
condition: Here is what the code looks
like:
'if then logic to check
condition
If
txtUserName.Text = "learningcomputer"
And
txtPassword.Text = "Passw0rd1"
Then
'Access
granted'
MsgBox( "Welcome to Visual Basic
2010")
In Plain English, the first line
(starting with If
txtUserName.Text ..) is looking for value
of learningcomputer in the txtUserName.Text (.text
property for text box txtUserName ) and value of
Passw0rd1in the txtPassword.Text (.text property for
text box txtPassword) then do this:
'Access granted'
This line starts with single
quote is just a comment to help the vb
developer
MsgBox("Welcome to Visual Basic
2010")
This line will output a message box
with the text, Welcome to Visual Basic 2010
Next we are going to look at the Else
block code shown below:
Else
'Access
denied'
MsgBox( "Please leave the
premises")
Me.Close()
Again in plain English, if the first
condition is not true, then the code after the Else is
executed.
'Access
denied' - just a comment
as in Fyi
MsgBox("Please leave the
premises")
Gives the user a message box with
Access denied info
Me.Close()
Closes the form (Form 1 in this case
also known as Me)
Ready to Execute
the VB Program?
Now that you understand
the basic mechanics of this login form, let us go ahead
and run the application. Before we do that, let us save
the project. You can do that by either doing
File > Save All or by clicking
floppy drives icon on the Toolbar.
When we did
that, we got the following dialog
box:
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We enter LoginScreen in the Name, Location
of c:\Temp and click Save. Now we can run the Visual
Basic project. You can execute a project by either
clicking on the Green play button on the Toolbar window
or selecting this from the File
Menu.
Debug > Start Debugging
(F5)
When we did that on our end, here
is what we see on our Putr. You can see data entry form
where you can enter username and password information.
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Enter the Username and Password:
Let's go ahead and enter the following
information:
Username:
learningcomputer
Password: Passw0rd1
Next you
can click on the Login button. If you did this right,
you should get the following VB dialog
box:
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Woohoo! Our program is now working just as
designed.
Notice two things:
1. In the
Title bar (highlighted in blue), it mentions that the
Program is Running
2. When you clicked on Login
button control, VB 2010 displayed the Welcome to Visual
Basic 2010 message box. In other words you have passed
the Login screen.
Subsequently we want to test
the else condition. All we need to do is to try another
username/password combination. When we did that, we got
the Access denied message shown right below.
After that Visual Basic closes the
form.
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What about the Cancel button?
One minor thing we forgot to mention. When the use
clicks on the Cancel button control, we would like to
close the application. Here is the code for that,
similar to the Else block.
'Close the
form
Me.Close()
This finishes the simple Login
Program for VB 2010.
h2Other important VB concepts:
We would like
to highlight a few other important concepts in Visual
Basic Language. Here are they:
Declaration of variables:In Visual Basic, you
declare variables to temporarily store values during the
execution of a program. Variables have a name and a data
type (which determines what kind of data the variable
can store). You declare a variable with the Dim
statement, supplying a name for the variable.
The syntax for declaring a variable
is
Dim variable name [As
type]
Where:
Variable
name: Name of the variable chosen by the Visual
Basic programmer
Type: One of the
many VB data types e.g. integer, string, data, variant
(default) etc.
Examples of VB
variables:
Dim strName
As
String
'string data type holds text
data
Dim intCust
As
Integer
'Assignment of
variables
strName = "Kash Money"
intCust = 4323
'Message Box displaying the variable
values
MsgBox( "Customer ID for
" & strName &
"
is " &
intCust)
First we declare two variables, one to
hold the name and the other to hold customer ID. Next we
assign value to these variables. Finally we display the
values using a Message box. One new item here is this
& symbol which is used to
concatenation (combining text together)
in VB 2010. You can add this code to a new btn control’s
click event like we have already showed you earlier.
After that you can execute the program and then click on
the btn control.
Here is what we see in our
Visual Basic code execution:
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We have highlighted the variables in red rectangle
for your understanding.
Visual Basic Loops (Repletion logic):Besides
conditional logic, a software program also needs to be
able to perform repetitive tasks. It may be that you
need to process items in a list or parse through
database records one at a time. In a software program,
this is typically achieved by some kind of looping. In
Visual Basic, you can repeat tasks by using one of these
three types on Loops:
1. For - Next
statements
2. Do - While statements
3. Do - Until
statements
Lets look a little
further into these.
For - Next statements:The For - Next loop
repeats a group of statements a specified number of
times. This type of loop is handy when you know exactly
how many times you need to repeat the action. The syntax
is as follows:
For Counter = Start To End
[step size]
statements
[Exit For]
Next
[counter]
Where:
Counter:
Variable (usually an integer) used to control the flow
of the loop
Start: Initial value of
the counter
End: Final value of the
counter
Step size: optional; the
amount the counter increases by every time the loop is
executed, typically 1
Exit For:
optional; statement to break out of the loop
Notice [
] are all optional statements
Example
of a For - Next statement:
In order
understand the Visual Basic For-Next loop, lets us use a
simple example. We will loop five times and simply
display the counter value in the Debug window. The Debug
window is typically used to trouble shoot issues in
Visual Basic programming code.
Here is what the
For - Next code looks like:
'declare the
variable
Dim intCount
As
Integer
'loop 5
times
For intCount = 1
To 5
'Write the counter value to the debug
window
Debug.WriteLine("Loop counter is now
" & intCount & vbCrLf)
Next
We start with declaration of intCount as an integer.
Next we open the For - Next loop with starting
value of intCount=1. We will use Debug.WriteLine to
display the counter value in the Debug window. vbCrLf is
constant value for carriage return character and line
feed character. Basically it force the program to go to
a new line. Then we loop through the procedure five
times.
When we run this piece of code, here is
what it looks like on our end:
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Do - Loop statementsUnlike the For - Next
loop, the Do - Loop statements repeat a block of
statements while a condition is true. You can important
Do - Loop by either using Do .. While or Do ..
Until loop. Lets look at one of them
next.
Do - While
statements
With Do - While statement,
you can have a Pre-test loop where the loop condition it
checked first. Here is syntax for a Pre-test Do .. While
statement.
Do While
condition
statements
[Exit Do]
Loop
For a Post-test loop when
the loop condition is check after the code, the syntax
is as follows:
Do
statements
[Exit Do]
Loop While
condition
Where:
Do:
Starts the loop
While condition:
Repeat the loop While this condition is
true
Exit Do: Optional; statement to
break out of the loop.
Example of a Do - While
statement:
We are going to create a VB
program where we are looking for a particular character
in an expression. Our expression is “Kash Money”
ofcourse. We would like to read one character at a time
using the VB MID
function. When we find a “M” we
would like to stop execution.
Here is what the
code looks like:
'declare the
variables
Dim intCount
As
Integer
Dim strName
As
String
strName = "Kash Money"
intCount = 1
'loop while the character is not
M
Do
While Mid(strName,
intCount, 1) <> "M"
'Write the counter value and the character
to Debug Window
Debug.WriteLine(intCount &
"," &
Mid(strName, intCount, 1))
intCount = intCount + 1
Loop
Lets us review the code. We
declare two variables, intCount to track counter value
and strName to store the expression. Next we assign
values to these. We start out the loop with this VB
code, Do While. We are also using MID function. You can
read more about this on this function page. Basically it
will read one character at a time in our expression,
“Kash Money”. As we are reading the values, we also
print the output to the Debug window. We are displaying,
the counter value and the character found by the MID
function. Finally we increment the counter by 1. This
will continue execution till it finds the character “M”
and then will stop.
After we execute this
program, here what our screen image
displays:
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Visual Basic Related Links:There are quite a
few items regarding Visual Basic that we did not cover.
However we have compiled a list of resources on VB that
will aid you in the learning process. Here it
is:
-What is Visual Basic
-Introduction
to Visual Basic
-Visual Basic home page
If you would like more information
about Visual Basic then the link below is a
useful one to look into.
http://vyaskn.tripod.com/sqlserverres.htm
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