Cross Ref > OOP Basics

In VB.Net, the Object keyword is an alias for the base System.Object class and is the single base class all classes ultimately inherit from. Use the Inherits keyword to indicate the parent class and Inherits must precede all declarations in a class.

Syntax Example:   'Specify both namespace and class: Public Class Cyborg Inherits System.Object End Class 'Use Object alias for System.Objct: Public Class Cyborg Inherits Object End Class 'Default when not specified is System.Object: Public Class Cyborg End Class

Declare and implement VB.Net classes after the form class or in their own .vb files. Unlike VB Classic, you can have more than one class in a .vb class file (VB classic uses .cls files for each class).

Public Class Cyborg

  Inherits Object

  Public Sub IntroduceYourself()

  MessageBox.Show("Hi, I do not have a name yet.")

 End Sub

End Class

Dim T1 As New Cyborg
T1.IntroduceYourself()

//No need to clean up with managed classes.

//The garbage collector will take care of it.

 VB.Net Class..Object (Class..End Class..New)

Ultra-primitive (no inheritance) but useful and encourages you to think and design using objects. Unlike VB, you can have more than one class per file.

Classes in ASP do support member fields, properties, and methods.

'Declare class.

Class Cyborg

  Public Function IntroduceYourself() 

    Response.Write("Hi, I do not have a name yet.") 

  End Function 

End Class

'Create object from class.

Set T1 = new Cyborg

T1.IntroduceYourself() 

Set T1 = Nothing      'Be sure to clean up!

 Creating a Class in ASP

VB.Net uses the Inherits keyword followed by the parent class name. If you do not include Inherits, your class inherits from System.Object.

Public Class Android

End Class

Public Class T-600

  Inherits Android

End Class

 VB.Net Inheritance (Inherits ParentClass)  

In VB.Net you can set the visibility of a member field to any visibility: private, protected, public, friend or protected friend.

You can intialize a member field with a default when declared. If you set the member field value in your constructor, it will override the default value.

Finally, you can use the Shared modifier (no instance required) and ReadOnly modifier (similar to a constant).

Public Class Cyborg
  Private FSerialNumber As String = "A100"

  Public CyborgName As String
  Public CyborgAge As Integer
 

  Public Shared ReadOnly SeriesID As Integer = 100
End Class

 VB.Net Member Field

ASP Classic does support member fields, but, as usual, you cannot initialize the type nor value of a member field. The type is implied by usage.

Class Cyborg

  Private FSerialNumber

  Public FCyborgName

  Public FCyborgAge 
  Public FSeriesID

End Class

VB.Net�uses the keywords sub and function. A sub does not return a value and a function does. Many programmers like to use the optional call keyword when calling a sub to indicate the call is to a procedure.

Public Class Cyborg

� Inherits Object

� Public Sub IntroduceYourself()

��� MessageBox.Show("Hi, I do not have a name yet.")

� End Sub

End Class

Dim T1 As New Cyborg
T1.IntroduceYourself()

ASP classic uses the keywords sub and function. A sub does not return a value and a function does. Many programmers like to use the optional call keyword when calling a sub to indicate the call is to a procedure.

'Declare class.

Class Cyborg

  Public Function IntroduceYourself() 

    Response.Write("Hi, I do not have a name yet.") 

  End Function 

End Class

'Create object from class.

Set T1 = new Cyborg

T1.IntroduceYourself() 

The method modifiers include�MustOverride,�NotOverridable, Overridable, Overrides. Specify�VB.Net member modifiers as follows:

Public Overrides Function SomeFunction() As Double

The field modifiers include ReadOnly and Shared. Specify field modifiers as follows:

Public ReadOnly SomeField As String

Other than visibility modifiers Public and Private, the only other member modifier available in ASP Classic is Default which is used only with the Public keyword in a class block. It indicates that the sub, function, or property is the default method for the class. You can have only one Default per class.

VB.Net uses a special property keyword along with special get and set methods to both get and set the values of properties. For a read-only property, leave out the set method. The value keyword is used to refer to the member field. Properties can make use of any of the access modifiers (private, protected, etc).

My preference for VB.Net code is to start member fields with "F" ("FName" in our example) and drop the "F" with properties that manage member fields ("Name" in our example).

Public Class Cyborg
  Private FCyborgName As String

  Public Property CyborgName()
    Get
      Return FCyborgName
    End Get

 
    Set(ByVal value)
      FCyborgName = value
    End Set
  End Property 

End Class

 VB.Net Member Property (property, get, set)

ASP classic uses the property keyword and special Get and Let methods to both get and set the values of properties.

Class Cyborg
 Private FCyborgName
 
 Public Property Get CyborgName()
  CyborgName = FCyborgName
 End Property

 Public Property Let CyborgName(pCyborgName)
  FCyborgName = pCyborgName
 End Property

End Class

 ASP Classic Member Property (Property..Get..Let)

In VB.Net, you specify each class and each class member's visibility with an access modifier preceding class or member. The VB.Net access modifiers are the traditional Public, Protected, and Private plus the two additional .Net modifiers Friend and Protected Friend.

Friend indicates members are accessible from types in the same assembly. Protected Friend indicates members are accessible from types in the same assembly as well as descendant classes. OO purist might object to Friend and Protected Friend and I suggest you avoid them until you both fully understand them and have a need that is best suited by them.

Public Class Cyborg
  Inherits Object

  Private FName As String

End Class

 VB.Net Access Modifiers

The member visibility modifiers are Private and Public. If not specified, the default is Public. Private and Public have the usual meaning. Private members are visible only within the class block. Public members are visible within the class and outside of the class.

Class Cyborg

  Private FSerialNumber  

  Public FCyborgName

  Public Function IntroduceYourself() 
    Response.Write("Hi, I do not have a name yet.") 
  End Function

End Class

 ASP Classic Member Visibility (Private, Public)