1 VB net-Language Fundamentals

VB.Net(Language

Fundamentals)

A simple VB.net program

Imports System

Public Module HelloModule

Public Sub Main()

Console.WriteLine(“HelloWorld!!!”)

End Sub

End Module

The Main() method

• A program's Main method can appear within a Visual Basic .NET module

• Because Visual Basic .NET modules are

classes wherein everything is shared, the Shared keyword is not used in such a declaration as in the previous example.

Saving,Compiling and Executing the Program

• Save the file with extension “.vb” .(Test.vb)

• Goto command window

• Compile the file :• vbc Test.vb

• After successful compilation .EXE file is created(Test.EXE)

• Execute the EXE file as “Test”

Execution result

Compiling the code

Creating your first VB windows application

Tool box

Form

Properties Box

Solution Explorer

Editing project settings

Writing the first windows application

On the button click write thisPrivate Sub Button1_Click(ByVal sender As

System.Object, ByVal e As System.EventArgs) Handles Button1.Click

MessageBox.Show("Hello World", _

"A first look at vb", _

MessageBoxButtons.OK, _

MessageBoxIcon.Information)

End Sub

Execution of the Program

ByVal and ByRef in VB.net• The word ByVal is short for “By Value”

• This means passing a copy of a variable to your Subroutine in which case changes that are made are made to the copy and the original will not be altered.

• ByRef is short for “By Reference”.

• This means that you are not handing over a copy of the original variable but pointing to the original variable.

Example • Let us consider the example

Dim Number1 As Integer Number1 = 10

Call IncrementVariable(Number1)MsgBox(Number1)-------------------------------------Private Sub IncrementVariable(ByVal Number1 As

Integer) Number1 = Number1 + 1

End Sub

• Try the code with ByRef Number1 as Integer as argument to the function

Fundamental Data Types in VBVB type Range

Boolean True or false

Byte 0 to 255 ( unsigned 8 bit)

Short -32768 to 32767 (signed 16 bit )

Char Any Unicode value (new to vb.net)

U0000 to Uffff (16 bit unicode character)

Date -The range of values is from midnight

on January 1, 0001 (0001-01-01T00:00:00) through 1 second before midnight on December

31, 9999 (9999-12-31T23:59:59).

VB type Range

Long 9223372036854775808 through

9223372036854775807.

Float 1.5*10-45 to 3.4*1038 (32 bit floating point number)

Double 5.0*10-324 to 1.7*10308 (64 bit floating point number)

Decimal 100 to 1028(96-bit signed number)

String Limited by system memory (Represents a set of unicode characters)

Single -3.40282347E38

through 3.40282347E38.(32 bit value) Object Any type can be stored in an object

variable(Base class of all types in .NET)

The System Data TypesVB type System Type Range

Byte System.Byte 0 to 255 ( unsigned 8 bit)

Short System.Int16 -32768 to 32767 (signed 16 bit )

Char System. Char Any Unicode character

U0000 to Uffff (16 bit unicode character)

Date System.DateTime -The range of values is from midnight

on January 1, 0001 (0001-01-01T00:00:00) through 1 second before midnight on December

31, 9999 (9999-12-31T23:59:59).

VB type System Type Range

Long System.Int64 9223372036854775808 through

9223372036854775807. Float System.Single 1.5*10-45 to 3.4*1038 (32 bit floating point

number)

Double System.Double 5.0*10-324 to 1.7*10308 (64 bit floating point number)

Boolean System.Boolean true or false

Decimal System.Decimal 100 to 1028(96-bit signed number)

String System.String Limited by system memory (Represents a set of unicode characters)

Single System.Single -3.40282347E38

through 3.40282347E38.(32 bit value)

Object System.Object Any type can be stored in an object variable(Base class of all types in .NET)

Type Conversion

Declaring and Initializing variables• We declare variables like this: Dim number1 As Integer

Dim number 2 As Integer

• We initialize the variables as: number1 = 3

number2 = 5

• Variable identifiers may be suffixed with type characters that serve to indicate the variable's type. The declaration can be rewritten as

Dim number1% and Dim number2%

List of type charecters

List of literal formats

Introducing Array Types• Array declaration and initialization

– Dim a(4) As Integer;– Dim a as String ={“first” ,”second”, “third”}

– Dim a(,) As Integer{{1,2},{3,4},{5,6}}

• The above declaration produces the following array:

a(0,0)=1 a(0,1)=2a(1,0)=3 a(1,1)=4a(2,0)=5 a(2,1)=6

• For Allocating arrays dynamically we use the “New” keyword

Dim a() As Integer a=New Integer(4){1,2,3,4}

• If the array elements won't be initialized by the allocation, it is still necessary to include the curly brackets:

Dim a( ) As Integer a = New Integer(5) {}

Can you figure out what is the meaning of:

Dim a() As Integer?

Access Modifiers

Operators

+ - / * ++ -- %

== <> < > >= <=TypeOf…IS

Is Like

&& || ! & | ^ ~

Relational Operators

Logical Operators

Arithmetic Operators

Shift Operators

>> <<

= >= <= *= /= &= |= ^= <<= >>= %=

Assignment Operators

Looping Statements

FOR Loop :

For variable = expression To expression [ Step

expression ]statements Next [ variable_list ]

• Eg: Dim answer As Integer

Dim startNumber As Integer

answer = 0

For startNumber = 1 To 4

answer = answer + startNumber

Next startNumber

MsgBox answer

do loopDo While [expression]

statements

Loop• Eg: Dim number as Integer

number = 1Do While number < 5

MsgBox numbernumber = number + 1

Loop

Do…Until loopDo Until [expression]

statements Loop

• Eg: Do Until number < 5

MsgBox numbernumber = number + 1

Loop

For Each For Each variable In expression

statements

Next [ variable ]

• EgDim a( ) As Integer = {1, 2, 3, 4, 5}

Dim b As Integer

For Each b In a

Console.WriteLine(b)

Next

Decision constructsIf/Else statement

If expression Then

statements

End If

also

If expression Then

statements

Else

statements

End If

Condition must evaluate to bool value

Select Case statements

Dim creamcake As StringDim DietState As String creamcake= TextBox1.TextSelect Case creamcake

Case "Eaten"DietState = "Diet Ruined"

Case "Not Eaten"DietState = "Diet Not Ruined"

Case ElseDietState = "Didn't check"

End SelectMsgBox DietState