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TRANSCRIPT
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Chapter 1
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Objectives
Identify VB.net as part of .Net framework
Declare variables and constants
Discuss programming constructs
Implement arrays
Discuss OO features of VB.net
Implement typecasting
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Features of VB.net
VB.net is:
A part of Visual Studio.net
A full-fledged object-oriented language
The only language in VS.net that providesbackground compilation
The only language in VS.net that supportslate binding
Not case-sensitive like C, C++, or Java
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Data types in VB.net
Category Data type Length(in bits)
Numeric Integer 32
Long 64
Decimal Decimal 128
Character Byte 8
Char 16
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Data types (Cont)
Category Data type Length(in bits)
String String -
Object Object -
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An Example
Dim d1 As Double
Dim d2 As Object
Dim d3, d4, d5 As IntegerDim mystring As String
Dim a As Integer = 5
d1 = 12
d2 = 10.5
d3 = 4
mystring = Jonathan
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Declaring Constants
Syntax to declare a constant is as follows:
[Public | Private | Friend | Protected |Prot
ected Friend]Constconstantname [As type]= expression
For example:
Public Const DaysInYear = 365
Private Const WorkDays = 250
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Programming Constructs
Decision statements
VB.net provides 3 decision statements:If ..then
If..then..else
Select..Case
If-then-elseIf-then
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An Example(1)
Dim KRA As Decimal
If KRA = 1 Then
Return Bonus * 0.1
ElseIf KRA = 2 Then
Return Bonus * 0.09
ElseIf KRA = 3 Then
Return Bonus * 0.07
ElseReturn 0
End If
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An Example(2)
Dim KRA As Decimal
Select Case KRA
Case 1 ' KRA is 1.
Return Bonus * 0.1
Case 2, 3 ' KRA is 2 or 3.Return Bonus * 0.09
Case 5 To 7 ' KRA is 5, 6, or 7.
Return Bonus * 0.07
Case 4, 8 To 10 ' KRA is 4, 8, 9, or 10.
Return Bonus * 0.05
Case Is < 15 ' KRA is 11, 12, 13, or 14.
Return 100Case Else ' KRA is < 1 or > 14.
Return 0
End Select
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Programming Constructs
Loop structures supported by VB.net are:
While
Do..Loop
For..Next
For Each..Next
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Example for Loops
Dim Cnt As Integer = 0
Dim Nbr As Integer = 10
While Nbr > 6
Nbr = Nbr - 1
Cnt = Cnt + 1
End While
Dim Cnt As Integer =0
Dim Nbr As Integer =10
Do While Nbr > 6
Nbr = Nbr 1
Cnt = Cnt + 1
Loop
While Loop Do..Loop
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Example for Loops -11
Dim Num1,Total AsInteger
For Num1= 1 To 5 Step 1
Total = Total + Num1
Next Num1
Dim X As Integer
For Each X In A
X = 128
Next X
For..Next For Each..Next
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Arrays
Arrays are objects in VB.net.
An array can be of any fundamental datatype, a structure, or an object class.
Array variables can have the Public,
Protected, Friend, Private, or ProtectedFriend specifier.
100
250
640
710Cynthia
Patrick
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Example for Arrays
Dim Expenditure(366) As Decimal
Dim I As Integer
For I = 0 to 365
Expenditure(I) = 20
Next I
Creates
Singledimensionalarray
The above code declares the array variable Expenditure, initializes it tohave 366 elements, and then assigns an initial value of 20 to eachelement.
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Example for arrays - 11
Dim EmpData(3) As Object
EmpData(0) = "astalavista"
EmpData(1) = "42 Heaven Towers"
EmpData(2) = 100
EmpData(3) = Format("09-10-1992", "Date")
Mixing data types in an array is possible if it is declared of typeObject. The following example stores employee information in thearray variable EmployeeData.
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Multidimensional Arrays
Dim Num1, Num2 As IntegerDim MDim0, MDim1 As IntegerDim MatA(10, 10) As Double
MDim0 = MatA.GetLength(0) 1MDim1 = MatA.GetLength(1) - 1
For Num1 = 0 To MDim0For Num2 = 0 To MDim1MatA(Num1, Num2) = (Num1 * 10) + Num2
Next Num2Next Num1
CreatesMulti-dimensionalarray
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Redim Statement
ReDim Preserve MyArray(5, 20)
The above statement allocates a new array, initializes itselements from the corresponding elements of the existing
MyArray, and assigns the new array to MyArray.
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Object-oriented Features
Object-oriented language
Abstraction Polymorphism
Encapsulation Inheritance
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Declaring Classes
A class is declared with the Class..End Class declarations.
An Example:
Public Class TestClass
End Class
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Option Statement Variations
Option statement Value Description
Option Explicit On Requires declaration of all thevariables before they are used
Off Variables can be used withoutdeclaring them (Default)
Option Compare Binary Strings are compared using textalgorithm
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Option Statement Variations-11
Optionstatement
Value Description
Option Strict On Automatic type correction will nottake place
Off Automatic type correction will takeplace (Default)
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Implementing Typecasting
Typecasting in VB.net is implemented by means ofthe Type() statement.
For example:
Dim Num1 As Long
Dim Num2 As Double
Num1 = 500
Num2 = CType(Num1,Double)