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Classes

VB.NET classes are the same in principle as they were in VB6. However, the way you create properties is different. Where you defined properties in VB like the example below.

Visual Basic 6.0
dim strComment as string
dim strName as string
		
Private Sub Class_Initialize()
   strName="PropertyClass"
End Sub

Public Property Get Comment() as string
    Comment = strComment
End Property

Public Property Get Name() as string
    Name = strName
End Property

Public Property Let Name(strNew as string)
    strName = strNew
End Property
GET/LET and SET operations were separate entities, now for VB.NET they're not. A LET property has been removed so that for the above, the code would look like :-

Visual Basic.NET
dim strComment as string
dim strName as string = "PropertyClass"
dim strTime as string

Public ReadOnly Property Comment As string
    Get
        Return strComment
    End Get
End Property

Public Property Name as string
    Get
        Return strName
    End Get
    Set (ByVal strNew as string)
        strTime = strNew
    End Set
End Property
As you can see from above, in the Comment Property, there is a ReadOnly word which tells the compiler not to look for a SET section of the property. For a property which can only have a property set and not got, use WriteOnly instead. Another new feature of VB.NET is inheritence, below is a code example :-

Visual Basic.NET 
Imports Microsoft.VisualBasic

Public Class clsItem 
    Private mlngID As long
    Private mdtBirthdate As date

    Public Overridable Property UID() As long
        Get 
            Return mlngID
        End Get 
        Set(ByVal Value As long)
            mlngID = Value 
        End Set 
    End Property 

    Public Overridable Property BirthDate() As Date 
        Get 
            Return mdtBirthDate 
        End Get 
        Set(ByVal Value As Date) 
            mdtBirthDate = Value 
        End Set 
    End Property 
End Class 

Public Enum eGender
    Female
    Male
End Enum

Public Class clsPerson:Inherits clsItem
    Private meGender As eGender 
    Private mstrName as string
    Private mdtBirthDate as date

    Public Overloads Property UID() As String 
        Get 
            Return mstrName 
        End Get 
        Set(ByVal Value As String) 
            mstrName = Value 
        End Set 
    End Property 

    Public Overrides Property BirthDate() As Date 
        Get 
            Return mdtBirthDate 
        End Get 
        Set(ByVal Value As Date) 
            mdtBirthDate = Value 
        End Set 
    End Property 

    Public Property Gender() As eGender
        Get 
            Return meGender 
        End Get 
        Set(ByVal Value As eGender) 
            meGender = Value 
        End Set 
    End Property 
End Class

Module One
    Sub Main()
	Dim objPerson as new clsPerson

	objPerson.UID = "Nigel Whitworth"
	
	System.console.write(objPerson.UID)

    End Sub
End Module
As you can see from the above example, there is Overrideable, Overloads and Overrides. They are all standard OO techniques. You can only override or overload a property from the base class that is overrideable. Overrides means this replaces the code in the base class. Overloads enables you have multiple functions that have the same name. The compiler runs the function that matches the parameters that is passed into the function.

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