Vb.net oops

VB.Net is an object-oriented
programming language. 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 describes
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. Depending 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:

Imports System
Public Class Rectangle
  Private length As Double
   Private width As Double
     Public methods
Public Sub AcceptDetails ()
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 As 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 created 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 is 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.
Shared 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 character 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 following are the VB.Net's
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
CUShort
Date
Decimal
Declare
Default
Delegate
Dim
DirectCast
Do
Double
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
Interface
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
ParamArray
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