VB - Tutorials Point

Visual Basic 2010 Express (VBE) Visual Web Developer The last two are free. Using these tools, you can write all kinds of VB.Net programs from simple command-line applications to more complex applications. Visual Basic Express and Visual Web Developer Express edition are trimmed down versions of Visual Studio and has the same look and feel.


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VB.NET VB.NET

2About the Tutorial

VB.Net is a simple, modern, object
-
oriented computer programming language developed by
Microsoft to combine the power of .NET Framework and the common language runtime with
the productivity benefits that a
re the hallmark of Visual Basic.

This tutorial will teach you basic VB.Net programming and will also take you through various
advanced concepts related to VB.Net programming language.

Audience

This tutorial has been prepared for the beginners to help them
understand basic VB.Net
programming. After completing this tutorial, you will find yourself at a moderate level of
expertise in VB.Net programming from where you can take yourself to next levels.

Prerequisites

VB.Net programming is very much based on BASIC

and Visual Basic programming languages,
so if you have basic understanding on these programming languages, then it will be a fun for
you to learn VB.Net programming language.

Copyright & Disclaimer

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e content and graphics published in this e
-
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Pvt.
Ltd. The user of this e
-
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art of the content of
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-
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ies or errors. Tutorials Point (I) Pvt.
Ltd. provides no guarantee regarding the accuracy, timeliness or completeness of our website
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tutorial, please notify us at

[email protected]

Table of Contents

About the Tutorial

................................
................................
................................
................................
...

1
VB.NET

3Audience

................................
................................
................................
................................
.................

1

Prerequisites

................................
................................
................................
................................
...........

1

Copyright & Disclaimer

................................
................................
................................
............................

1

Table of Contents

................................
................................
................................
................................
....

2

1.

VB.NET
–

OVERVIEW

................................
................................
................................
...........

8

Strong Programming Features VB.Net

................................
................................
................................
.....

8

2.

VB.NET
–

ENVIRONMENT

SETUP

................................
................................
.......................

10

The .Net Framework

................................
................................
................................
.............................

10

Integrated Development Environment (IDE) For VB.Net

................................
................................
.......

11

Writing VB.Net Programs on L
inux or Mac OS

................................
................................
.......................

11

3.

VB.NET
–

PROGRAM STR
UCTURE

................................
................................
......................

12

VB.Net Hello World Example

................................
................................
................................
.................

12

Compile & Execute VB.Net Program

................................
................................
................................
......

13

4.

VB.NET
–

BASIC SYNTA
X

................................
................................
................................
....

15

A Rectangle Class in VB.Net

................................
................................
................................
...................

15

Identifiers

................................
................................
................................
................................
..............

17

VB.Net Keywords

................................
................................
................................
................................
..

17

5.

VB.NET
–

DATA TYPES

................................
................................
................................
........

19

Data Types Available in VB.Net

................................
................................
................................
.............

19

Example

................................
................................
................................
................................
................

21

The Type Conversion Functions in VB.Net

................................
................................
.............................

22

Example

................................
................................
................................
................................
................

24

6.

VB.NET
–

VARIABLES

................................
................................
................................
..........

25
VB.NET

4Variable Declaration in VB.Net

................................
................................
................................
..............

25

Variable Initialization in VB.Net

................................
................................
................................
............

27

Example

................................
................................
................................
................................
................

27

Accepting Values from User

................................
................................
................................
..................

28

Lvalues and Rvalues

................................
................................
................................
..............................

28

7.

VB.NET
–

CONSTANTS A
ND ENUMERATIONS

................................
................................
....

30

Declaring Constants

................................
................................
................................
..............................

30

Example

................................
................................
................................
................................
................

31

Print and Display Constants in VB.Net

................................
................................
................................
...

31

Declaring Enumerations

................................
................................
................................
........................

32

Example

................................
................................
................................
................................
................

33

8.

VB.NET
–

MODIFIERS

................................
................................
................................
.........

35

List of Available Modifiers in VB.Net

................................
................................
................................
.....

35

9.

VB.NET
–

STATEMENTS

................................
................................
................................
......

40

Declaration Statements

................................
................................
................................
.........................

40

Executable Statements

................................
................................
................................
..........................

44

10.

VB.NET
–

DIRECTIVES
................................
................................
................................
.........

45

Compiler Directives in VB.Net

................................
................................
................................
...............

45

11.

VB.NET
–

OPERATORS

................................
................................
................................
........

50

Arithmetic Operators

................................
................................
................................
............................

50

Example

................................
................................
................................
................................
................

51

Comparison Operators

................................
................................
................................
..........................

52

Logical/Bitwise Operators

................................
................................
................................
.....................

54
VB.NET

5Example

................................
................................
................................
................................
................

55

Bit Shift Operators

................................
................................
................................
................................

57

Example

................................
................................
................................
................................
................

59

Assignment Operators
................................
................................
................................
...........................

60

Example

................................
................................
................................
................................
................

61

Miscellaneous Oper
ators

................................
................................
................................
......................

62

Example

................................
................................
................................
................................
................

63

Operators Precedence in VB.Net

................................
................................
................................
...........

64

Example

................................
................................
................................
................................
................

65

12.

VB.NET
–

DECISION MA
KING

................................
................................
.............................

67

If...Then Statement

................................
................................
................................
...............................

68

If...Then...Else Statement

................................
................................
................................
......................

70

The If...Else If...Else Statement

................................
................................
................................
..............

71

Nested If Statements

................................
................................
................................
.............................

73

Select Case State
ment

................................
................................
................................
...........................

74

Nested Select Case Statement

................................
................................
................................
...............

76

13.

VB.NET
–

LOOPS

................................
................................
................................
................

78

Do Loop

................................
................................
................................
................................
.................

79

For...Next Loop
................................
................................
................................
................................
......

82

Each...Next Loop

................................
................................
................................
................................
...

85

While... End While Loop

................................
................................
................................
........................

86

With... End With Statement

................................
................................
................................
..................

88

Nested Loops

................................
................................
................................
................................
........

89

Loop Control Statements
................................
................................
................................
.......................

91
VB.NET

6Exit Statement

................................
................................
................................
................................
......

92

Continue Statement

................................
................................
................................
..............................

94

GoTo Statement

................................
................................
................................
................................
....

95

14.

VB.NET
–

STRINGS

................................
................................
................................
.............

98

Creating a String Objec

................................
................................
................................
..........................

98

Properties of the String Class

................................
................................
................................
................

99

Methods of the String Class

................................
................................
................................
...................

99

Examples

................................
................................
................................
................................
.............

105

15.

VB.NET
–

DATE & TIME

................................
................................
................................
....

108

Properties and Methods of the DateTime Structure

................................
................................
............

109

Creating a DateTime Object

................................
................................
................................
................

112

Getting the Current Date

and Time

................................
................................
................................
.....

113

Formatting Date

................................
................................
................................
................................
..

114

Predefined Date/Time Formats

................................
................................
................................
...........

115

Properties a
nd Methods of the DateAndTime Class

................................
................................
............

117

16.

ARRAYS

................................
................................
................................
............................

121

Creating Arrays in VB.Net

................................
................................
................................
....................

121

Dynamic Arrays

................................
................................
................................
................................
...

122

Multi
-
Dimensional Arrays

................................
................................
................................
...................

124

Jagged Array
................................
................................
................................
................................
........

125

The Arra
y Class

................................
................................
................................
................................
....

126

17.

VB.NET
–

COLLECTIONS

................................
................................
................................
...

131

Various Collection Classes and Their Usage

................................
................................
.........................

131
VB.NET

7ArrayList

................................
................................
................................
................................
..............

132

Hashtable

................................
................................
................................
................................
............

136

SortedList

................................
................................
................................
................................
............

138

Stack

................................
................................
................................
................................
...................

142

Queue

................................
................................
................................
................................
.................

144

BitArray

................................
................................
................................
................................
...............

146

18.

VB.NET
–

FUNCTIONS

................................
................................
................................
......

150

Defining a Function

................................
................................
................................
.............................

150

Example

................................
................................
................................
................................
..............

150

Function Returning a Value

................................
................................
................................
.................

151

Recursive Function

................................
................................
................................
..............................

152

Param Arrays

................................
................................
................................
................................
......

153

Passing Arrays as Function Arguments

................................
................................
................................

153

19.

VB.NET
–

SUB PROCEDU
RES

................................
................................
............................

155

Defining Sub Procedures

................................
................................
................................
.....................

155

Example

................................
................................
................................
................................
..............

155

Pass
ing Parameters by Value

................................
................................
................................
..............

156

Passing Parameters by Reference
................................
................................
................................
........

157

20.

VB.NET
–

CLASSES & O
BJECTS
................................
................................
..........................

159

Class Definition

................................
................................
................................
................................
...

159

Member Functions and Encapsulation

................................
................................
................................

161

Constructors and Destructors

................................
................................
................................
..............

162

Shared Members of a VB.Net Class

................................
................................
................................
.....

165

Inheritance

................................
................................
................................
................................
..........

166
VB.NET

8Base & Derived Classes
................................
................................
................................
........................

166

Base Class Initialization

................................
................................
................................
.......................

168

21.

VB.NET
–

EXCEPTION H
ANDLING

................................
................................
.....................

170

Syntax

................................
................................
................................
................................
.................

170

Exception Classes in .Net Framework

................................
................................
................................
..

171

Handling Exceptions

................................
................................
................................
............................

172

Creating User
-
Defined Exceptions

................................
................................
................................
.......

173

Throwing Objects

................................
................................
................................
................................

174

22.

VB.NET
–

FILE HANDLI
NG

................................
................................
................................

175

Binary Files

................................
................................
................................
................................
..........

182

23.

VB.NET
–

BASIC CONTR
OLS
................................
................................
..............................

192

24.

VB.NET
–

DIALOG BOXE
S

................................
................................
................................
.

285

25.

VB.NET
–

ADVANCED FO
RM

................................
................................
............................

307

26.

VB.NET
–

EVENT HANDL
ING

................................
................................
............................

330

27.

VB.NET
–

REGULAR EXP
RESSIONS

................................
................................
....................

336

28.

VB.NET

–

DATABASE ACCESS

................................
................................
...........................

350

29.

VB.NET
–

EXCEL SHEET

................................
................................
................................
....

365

30.

VB.NET
–

SEND EMAIL

................................
................................
................................
.....

370

31.

VB.NET
–

XML PROCESS
ING

................................
................................
.............................

376

32.

VB.NET
–

WEB PROGRAM
MING

................................
................................
......................

391

VB.NET

9V
isual Basic .NET (VB.NET) is an object
-
oriented computer programming language
implem
ented on the .NET Framework. Although it is an evolution of classic Visual Basic
language, it is not backwards
-
compatible with VB6, and any code written in the old version
does not compile under VB.NET.

Like all other .NET languages, VB.NET has complete su
pport for object
-
oriented concepts.
Everything in VB.NET is an object, including all of the primitive types (Short, Integer, Long,
String, Boolean, etc.) and user
-
defined types, events, and even assemblies. All objects
inherits from the base class Object.

VB.NET is implemented by Microsoft's .NET framework. Therefore, it has full access to all the
libraries in the .Net Framework. It's also possible to run VB.NET programs on Mono, the open
-
source alternative to .NET, not only under Windows, but even Linux or

Mac OSX.

The following reasons make VB.Net a widely used professional language:



Modern, general purpose.

Object oriented.

Component oriented.

Easy to learn.

Structured language.

It produces efficient programs.

It can be compiled on a variety of comp
uter platforms.

Part of .Net Framework.

Strong Programming Features VB.Net

VB.Net has numerous strong programming features that make it endearing to multitude of
programmers worldwide. Let us mention some of these features:



Boolean Conditions

Automatic G
arbage Collection

Standard Library1.

VB.NET
–

Overview
VB.NET

10

Assembly Versioning



Properties and Events

Delegates and Events Management

Easy
-
to
-
use Generics

Indexers

Conditional Compilation

Simple Multithreading

VB.NET

11I
n this chapter, we will discuss the

tools available for creating VB.Net applications.

We have already mentioned that VB.Net is part of .Net framework and used for writing .Net
applications. Therefore before discussing the available tools for running a VB.Net program,
let us understand how V
B.Net relates to the .Net framework.

The .Net Framework

The .Net framework is a revolutionary platform that helps you to write the following types of
applications:



Windows applications

Web applications

Web services

The .Net framework applications are mul
ti
-
platform applications. The framework has been
designed in such a way that it can be used from any of the following languages: Visual Basic,
C#, C++, Jscript, and COBOL, etc.

All these languages can access the framework as well as communicate with each o
ther.

The .Net framework consists of an enormous library of codes used by the client languages
like VB.Net. These languages use object
-
oriented methodology.

Following are some of the components of the .Net framework:



Common Language Runtime (CLR)

The .Net

Framework Class Library

Common Language Specification

Common Type System

Metadata and Assemblies

Windows Forms

ASP.Net and ASP.Net AJAX

ADO.Net2.

VB.NET
–

Environment

Setup
VB.NET

12

Windows Workflow Foundation (WF)

Windows Presentation Foundation

Windows Communication Foundation (WCF
)

LINQ

For the jobs each of these components perform, please see

ASP.Net
-

Introduction
,
and for
details of each component, please consult Microsoft's documentation.

Integrated Development
Environment (IDE) For VB.Net

Microsoft provides the following development tools for VB.Net programming:



Visual Studio 2010 (VS)

Visual Basic 2010 Express (VBE)

Visual Web Developer

The last two are free. Using these tools, you can write all kinds of VB.N
et programs from
simple command
-
line applications to more complex applications. Visual Basic Express and
Visual Web Developer Express edition are trimmed down versions of Visual Studio and has
the same look and feel. They retain most features of Visual Stu
dio. In this tutorial, we have
used Visual Basic 2010 Express and Visual Web Developer (for the web programming
chapter).

You can download it
from

here
. It gets automatically

i
nstalled in your machine. Please note
that you need an active internet connection for installing the express edition.

Writing VB.Net Programs on Linux or Mac OS

Although the

.NET Framework runs on the Windows operating system, there are some
alternative ve
rsions that work on other operating systems. Mono is an open
-
source version
of the .NET Framework which includes a Visual Basic compiler and runs on several operating
systems, including various flavors of Linux and Mac OS. The most recent version is VB 201
2.

The stated purpose of Mono is not only to be able to run Microsoft .NET applications cross
-
platform, but also to bring better development tools to Linux developers. Mono can be run on
many operating systems including Android, BSD, iOS, Linux, OS X, Wind
ows, Solaris and
UNIX.
VB.NET

13B
efore we study basic building blocks of the VB.Net programming language, let us look a bare
minimum VB.Net program structure so that we can take it as a reference in upcoming
chapters.

VB.Net Hello World E
xample

A VB.Net program basically consists of the following parts:



Namespace declaration

A class or module

One or more procedures

Variables

The Main procedure

Statements & Expressions

Comments

Let us look at a simple code that would print the words "
Hello World":

Imports System

Module Module1


'This program will display Hello World


Sub Main()


Console.WriteLine("Hello World")


Console.ReadKey()


End Sub

End Module

When the above code is compiled and executed, it produces the followin
g result:

Hello, World!3.

VB.NET
–

Program Structure
VB.NET

14Let us look various parts of the above program:



The first line of the program

Imports System

is used to include the System
namespace in the program.



The next line has a

Module

declaration, the module

Module1
. VB.Net is completely
ob
ject oriented, so every program must contain a module of a class that contains the
data and procedures that your program uses.

Classes or Modules generally would contain more than one procedure. Procedures
contain the executable code, or in other words, t
hey define the behavior of the class.
A procedure could be any of the following:

o

Functiono

Subo

Operatoro

Geto

Seto

AddHandlero

RemoveHandlero

RaiseEvent



The next line

(
'This program) will be ignored by the compiler and it has been put to
add additional co
mments in the program.

The next line defines the Main procedure, which is the entry point for all VB.Net
programs. The Main procedure states what the module or class will do when executed.

The Main procedure specifies its behavior with the statement

Cons
ole.WriteLine

("Hello World")

WriteLine

is a method of the

Console

class
defined in the

System

namespace. This statement causes the message "Hello, World!"
to be displayed on the screen.

The last line

Console.ReadKey()

is for the VS.NET Users. This will p
revent the screen
from running and closing quickly when the program is launched from Visual
Studio .NET.

Compile & Execute VB.Net Program

If you are using Visual Studio.Net IDE, take the following steps:



Start Visual Studio.

VB.NET

15

On the menu bar, choose File



New



Project.

Choose Visual Basic from templates

Choose Console Application.

Specify a name and location for your project using the Browse button, and then choose
the OK button.

The new project appears in Solution Explorer.

Write code in the Code Ed
itor.

Click the Run button or the F5 key to run the project. A Command Prompt window
appears that contains the line Hello World.

You can compile a VB.Net program by using the command line instead of the Visual Studio
IDE:



Open a text editor and add the ab
ove mentioned code.

Save the file as

helloworld.vb

Open the command prompt tool and go to the directory where you saved the file.

Type

vbc helloworld.vb

and press enter to compile your code.

If there are no errors in your code the command prompt will t
ake you to the next line
and would generate

helloworld.exe

executable file.

Next, type

helloworld

to execute your program.

You will be able to see "Hello World" printed on the screen.
VB.NET

16V
B.Net is an object
-
oriented programming languag
e. In Object
-
Oriented Programming
methodology, a program consists of various objects that interact with each other by means
of actions. The actions that an object may take are called methods. Objects of the same kind
are said to have the same type or, more

often, are said to be in the same class.

When we consider a VB.Net program, it can be defined as a collection of objects that
communicate via invoking each other's methods. Let us now briefly look into what do class,
object, methods
,

and instant variables

mean.



Object

-

Objects have states and behaviors. Example: A dog has states
-

color, name,
breed as well as behaviors
-

wagging, barking, eating, etc. An object is an instance of
a class.

Class

-

A class can be defined as a template/blueprint that descri
bes the
behaviors/states that object of its type support.

Methods

-

A method is basically a behavior. A class can contain many methods. It is
in methods where the logics are written, data is manipulated and all the actions are
executed.

Instant Variables

-

Each object has its unique set of instant variables. An object's
state is created by the values assigned to these instant variables.

A Rectangle Class in VB.Net

For example, let us consider a Rectangle object. It has attributes like length and width.
De
pending upon the design, it may need ways for accepting the values of these attributes,
calculating area and displaying details.

Let us look at an implementation of a Rectangle class and discuss VB.Net basic syntax on the
basis of our observations in it:

I
mports System

Public Class Rectangle


Private length As Double


Private width As Double
'Public methods


Public Sub AcceptDetails()

4.

VB.NET
–

Basic Syntax
VB.NET

17
length = 4.5


width = 3.5


End Sub
Public Function GetArea() As Double


GetArea
= length * width


End Function


Public Sub Display()


Console.WriteLine("Length: {0}", length)


Console.WriteLine("Width: {0}", width)


Console.WriteLine("Area: {0}", GetArea())
End Sub
Shared Sub Main()


Dim r A
s New Rectangle()


r.Acceptdetails()


r.Display()


Console.ReadLine()


End Sub

End Class

When the above code is compiled and executed, it produces the following result:

Length: 4.5

Width: 3.5

Area: 15.75

In previous chapter, we crea
ted a Visual Basic module that held the code. Sub Main indicates
the entry point of VB.Net program. Here, we are using Class that contains both code and data.
You use classes to create objects. For example, in the code, r is a Rectangle object.

An object i
s an instance of a class:

Dim r As New Rectangle()

A class may have members that can be accessible from outside class, if so specified. Data
members are called fields and procedure members are called methods.
VB.NET

18Shared

methods or

static

methods can be invoked

without creating an object of the class.
Instance methods are invoked through an object of the class:

Shared Sub Main()


Dim r As New Rectangle()


r.Acceptdetails()


r.Display()


Console.ReadLine()

End Sub

Identifiers

An identifier is a name used
to identify a class, variable, function, or any other user
-
defined
item. The basic rules for naming classes in VB.Net are as follows:



A name must begin with a letter that could be followed by a sequence of letters, digits
(0
-

9) or underscore. The first c
haracter in an identifier cannot be a digit.

It must not contain any embedded space or symbol like ?
-

+! @ # % ^ & * ( ) [ ]
{ } . ; : " ' / and
\
. However, an underscore ( _ ) can be used.

It should not be a reserved keyword.

VB.Net Keywords

The follow
ing table lists the VB.Net reserved keywords:

AddHandler

AddressOf

Alias

And

AndAlso

As

Boolean

ByRef

Byte

ByVal

Call

Case

Catch

CBool

CByte

CChar

CDate

CDec

CDbl

Char

CInt

Class

CLng

CObj

Const

Continue

CSByte

CShort

CSng

CStr

CType

CUInt

CULng

CUShor
t

Date

Decimal

Declare

Default

Delegate

Dim

DirectCast

Do
VB.NET

19D
ouble

Each

Else

ElseIf

End

End If

Enum

Erase

Error

Event

Exit

False

Finally

For

Friend

Function

Get

GetType

GetXML

Namespace

Global

GoTo

Handles

If

Implements

Imports

In

Inherits

Integer

Inte
rface

Is

IsNot

Let

Lib

Like

Long

Loop

Me

Mod

Module

MustInherit

MustOverride

MyBase

MyClass

Namespace

Narrowing

New

Next

Not

Nothing

Not

Inheritable

Not

Overridable

Object

Of

On

Operator

Option

Optional

Or

OrElse

Overloads

Overridable

Overrides

ParamAr
ray

Partial

Private

Property

Protected

Public

RaiseEvent

ReadOnly

ReDim

REM

Remove

Handler

Resume

Return

SByte

Select

Set

Shadows

Shared

Short

Single

Static

Step

Stop

String

Structure

Sub

SyncLock

Then

Throw

To

True

Try

TryCast

TypeOf

UInteger

While

Widening

With

WithEvents

WriteOnly

Xor
VB.NET

20D
ata types refer to an extensive system used for declaring variables or functions of different
types. The type of a variable determines how much space it occupies in storage and how the
bit pa
ttern stored is interpreted.

Data Types Available in VB.Net

VB.Net provides a wide range of data types. The following table shows all the data types
available:

Data Type

Storage Allocation

Value Range

Boolean

Depends on
implementing
platform

True

or

False

Byte

1 byte

0 through 255 (unsigned)

Char

2 bytes

0 through 65535 (unsigned)

Date

8 bytes

0:00:00 (midnight) on January 1, 0001 through
11:59:59 PM on December 31, 9999

Decimal

16 bytes

0 through +/
-
79,228,162,514,264,337,593,543,950,335
(+/
-
7.9...E+2
8) with no decimal point; 0
through +/
-
7.9228162514264337593543950335 with 28
places to the right of the decimal

Double

8 bytes

-
1.79769313486231570E+308 through
-
4.94065645841246544E
-
324, for negative
values

4.94065645841246544E
-
324 through
1.79769313486
231570E+308, for positive
values

5.

VB.NET
–

Data Types
VB.NET

21Integer

4 bytes

-
2,147,483,648 through 2,147,483,647
(signed)

Long

8 bytes

-
9,223,372,036,854,775,808 through
9,223,372,036,854,775,807(signed)

Object

4 bytes on 32
-
bit
platform

8 bytes on 64
-
bit
platform

Any type can be

stored in a variable of type
Object

SByte

1 byte

-
128 through 127 (signed)

Short

2 bytes

-
32,768 through 32,767 (signed)

Single

4 bytes

-
3.4028235E+38 through
-
1.401298E
-
45 for
negative values;

1.401298E
-
45 through 3.4028235E+38 for
positive values

St
ring

Depends on
implementing
platform

0 to approximately 2 billion Unicode characters

UInteger

4 bytes

0 through 4,294,967,295 (unsigned)

ULong

8 bytes

0 through 18,446,744,073,709,551,615
(unsigned)

User
-
Defined

Depends on
implementing
platform

Each me
mber of the structure has a range
determined by its data type and independent of
the ranges of the other members

UShort

2 bytes

0 through 65,535 (unsigned) VB.NET

22Example

The following example demonstrates use of some of the types:

Module DataTypes


Sub Mai
n()


Dim b As Byte


Dim n As Integer


Dim si As Single


Dim d As Double


Dim da As Date


Dim c As Char


Dim s As String


Dim bl As Boolean


b = 1


n = 1234567


si = 0.12345678901234566


d = 0.1234
5678901234566


da = Today


c = "U"c


s = "Me"


If ScriptEngine = "VB" Then


bl = True


Else


bl = False


End If


If bl Then


'the oath taking


Console.Write(c & " and," & s & vbCrLf)



Console.WriteLine("declaring on the day of: {0}", da)


Console.WriteLine("We will learn VB.Net seriously")


Console.WriteLine("Lets see what happens to the floating point
variables:")


Console.WriteLine("The Single: {0}, The

Double: {1}", si, d)


End If
VB.NET

23
Console.ReadKey()


End SubEnd Module

When the above code is compiled and executed, it produces the following result:

U and, Me

declaring on the day of: 12/4/2012 12:00:00 PM

We will learn VB.Net seriously

Lets s
ee what happens to the floating point variables:

The Single:0.1234568, The Double: 0.123456789012346

The Type Conversion Functions in VB.Net

VB.Net provides the following in
-
line type conversion functions:

S.N

Functions & Description

1

CBool(expression)

C
onverts the expression to Boolean data type.

2

CByte(expression)

Converts the expression to Byte data type.

3

CChar(expression)

Converts the expression to Char data type.

4

CDate(expression)

Converts the expression to Date data type

5

CDbl(expression)

Converts the expression to Double data type.
VB.NET

246

CDec(expression)

Converts the expression to Decimal data type.

7

CInt(expression)

Converts the expression to Integer data type.

8

CLng(expression)

Converts the expression to Long data type.

9

CObj(expressi
on)

Converts the expression to Object type.

10

CSByte(expression)

Converts the expression to SByte data type.

11

CShort(expression)

Converts the expression to Short data type.

12

CSng(expression)

Converts the expression to Single data type.

13

CStr(exp
ression)

Converts the expression to String data type.

14

CUInt(expression)

Converts the expression to UInt data type.

15

CULng(expression)

Converts the expression to ULng data type.
VB.NET

2516

CUShort(expression)

Converts the expression to UShort data type.

Example

The following example demonstrates some of these functions:

Module DataTypes


Sub Main()


Dim n As Integer


Dim da As Date


Dim bl As Boolean = True


n = 1234567


da = Today


Console.WriteLine(bl)


Console.Write
Line(CSByte(bl))


Console.WriteLine(CStr(bl))


Console.WriteLine(CStr(da))


Console.WriteLine(CChar(CChar(CStr(n))))


Console.WriteLine(CChar(CStr(da)))


Console.ReadKey()


End Sub

End Module

When the above code is compiled and e
xecuted, it produces the following result:

True

-
1

True

12/4/20121

1

VB.NET

26A

variable is nothing but a name given to a storage area that our programs can manipulate.
Each variable in VB.Net has a specific type, which determines the size and
layout of the
variable's memory; the range of values that can be stored within that memory; and the set
of operations that can be applied to the variable.

We have already discussed various data types. The basic value types provided in VB.Net can
be categor
ized as:

Type

Example

Integral types

SByte, Byte, Short, UShort, Integer, UInteger, Long, ULong and
Char

Floating point types

Single and Double

Decimal types

Decimal

Boolean types

True or False values, as assigned

Date types

DateVB.Net also allows
defining other value types of variable like

Enum

and reference types of
variables like

Class
. We will discuss date types and Classes in subsequent chapters.

Variable Declaration in VB.Net

The

Dim

statement is used for variable declaration and storage alloc
ation for one or more
variables. The Dim statement is used at module, class, structure, procedure
,

or block level.

Syntax for variable declaration in VB.Net is:

[ ibute&#x att;&#xr120;list ] [ accessmodifier ] [[ Shared ] [ Shadows ] | [ Static ]]

[ ReadOnly ] Dim
[ WithEvents ] variablelist

Where,



attributelist

is a list of attributes that apply to the variable. Optional.

6.

VB.NET
–

Variables
VB.NET

27


accessmodifier

defines the access levels of the variables, it has values as
-

Public,
Protected, Friend, Protected Friend and Private. Optional.

Shared

declares a shared variable, which is not associated with any specific instance
of a class or structure, rather available to all the instances of the class or structure.
Optional.

Shadows

indicate that the variable re
-
declares and hides an identic
ally named
element, or set of overloaded elements, in a base class. Optional.

Static

indicates that the variable will retain its value, even when the after termination
of the procedure in which it is declared. Optional.

ReadOnly

means the variable can be

read, but not written. Optional.

WithEvents

specifies that the variable is used to respond to events raised by the
instance assigned to the variable. Optional.

Variablelist

provides the list of variables declared.

Each variable in the variable list has
the following syntax and parts:

variablename[ ( [ boundslist ] ) ] [ As [ New ] datatype ] [ = initializer ]

Where,



variablename
: is the name of the variable

boundslist
: optional. It provides list of bounds of each dimension of an array variable.

New
: op
tional. It creates a new instance of the class when the Dim statement runs.

datatype
: Required if Option Strict is On. It specifies the data type of the variable.

initializer
: Optional if New is not specified. Expression that is evaluated and assigned
to

the variable when it is created.

Some valid variable declarations along with their definition are shown here:

Dim StudentID As Integer

Dim StudentName As String

Dim Salary As Double

Dim count1, count2 As Integer

Dim status As Boolean

Dim exitButton As New

System.Windows.Forms.Button
VB.NET

28Dim lastTime, nextTime As Date

Variable Initialization in VB.Net

Variables are initialized (assigned a value) with an equal sign followed by a constant
expression. The general form of initialization is:

variable_name = value;

f
or example,

Dim pi As Double

pi = 3.14159

You can initialize a variable at the time of declaration as follows:

Dim StudentID As Integer = 100

Dim StudentName As String = "Bill Smith"

Example

Try the following example which makes use of various types of var
iables:

Module variablesNdataypes


Sub Main()


Dim a As Short


Dim b As Integer


Dim c As Double


a = 10


b = 20


c = a + b


Console.WriteLine("a = {0}, b = {1}, c = {2}", a, b, c)


Console.ReadLine()


End Sub

En
d Module VB.NET

29When the above code is compiled and executed, it produces the following result:

a = 10, b = 20, c = 30

Accepting Values from User

The Console class in the System namespace provides a function

ReadLine

for accepting input
from the user and store
it into a variable. For example,

Dim message As String

message = Console.ReadLine

The following example demonstrates it:

Module variablesNdataypes


Sub Main()


Dim message As String


Console.Write("Enter message: ")


message = Console.Read
Line


Console.WriteLine()


Console.WriteLine("Your Message: {0}", message)


Console.ReadLine()


End Sub

End Module

When the above code is compiled and executed, it produces the following result (assume the
user inputs Hello World):

Enter m
essage: Hello World

Your Message: Hello World

Lvalues and Rvalues

There are two kinds of expressions:



lvalue :

An expression that is an lvalue may appear as either the left
-
hand or right
-
hand side of an assignment.

rvalue :

An expression that is an rva
lue may appear on the right
-

but not left
-
hand
side of an assignment.
VB.NET

30Variables are lvalues and so may appear on the left
-
hand side of an assignment. Numeric
literals are rvalues and so may not be assigned and can not appear on the left
-
hand side.
Followin
g is a valid statement:

Dim g As Integer = 20

But following is not a valid statement and would generate compile
-
time error:

20 = g VB.NET

31End of ebook preview

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