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Polymorphism is a must in VB.NET

Not implementing polymorphism can lead to worse nightmares and headaches than implementing it, in terms of maintainance and extensibility.

This tip was submitted to the VS.NET Info Center by member William T. Please let other users know how useful it is by rating it below. Do you have a tip or code of your own you'd like to share? Submit it here.

There was a recent tip published here that was titled "Polymorphism can lead to head scratching in VB.NET.

I would like to stress that VB.NET is a fully compliant object-oriented language, and thus OOP should be practiced at all times within .NET development, albeit with careful planning and design in order not to lose focus.

In the tip mentioned above, the author stressed that polymorphism can lead to nightmares and headaches. I would like to stress that NOT implementing polymorphism can lead to worse nightmares and headaches, in terms of maintainance and extensibility.

The above problem, as stated by the tip author, can essentially be solved with the VB.NET keyword: MyClass.

I will replicate the exact same codes as first published in the original tip and I will put in the keyword in the appropriate place.

Let's see some code below:

    Class Parent
        Public Overridable Sub p1()
        End Sub

        Public Sub p2()

'Please note the MyClass implementation here. This will essentially call the 
base class wherein the keyword MyClass appears.

        End Sub
    End Class

    Class Child
        Inherits Parent

        Public Overrides Sub p1()
        End Sub
    End Class

    Sub Main()

        Dim p As Parent
        Dim c As Child

        p = New Parent()
        p.p1() 'OK
        p.p2() 'OK

        p = New Child()
        p.p1() 'OK
        p.p2() 'OK

        c = New Child()
        c.p1() 'OK
        c.p2() 'OK

    End Sub

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