Convert inheritance with interface from C# to VB.NET

Question

How can I convert following code to VB.NET?

class A
{
    public int NumberA { get; set; }
}

class B : A, I
{
    public int NumberB { get; set; }
}

interface I
{
    int NumberA { get; set; }
    int NumberB { get; set; }
}

In VB.NET there is problem with Implements keyword after property declaration. So I need to do something like this:

Class B
    Inherits A
    Implements IC

    Public Property NumberB() As Integer Implements IC.NumberB
    Get
        Return m_NumberB
    End Get
    Set(ByVal value As Integer)
        m_NumberB = value
    End Set
    End Property
    Private m_NumberB As Integer

    Public Property NumberA1() As Integer Implements IC.NumberA
    Get
        Return MyBase.NumberA
    End Get
    Set(ByVal value As Integer)
        MyBase.NumberA = value
    End Set
    End Property
End Class

But there is duplicit misleading property NumberA1. Is there some way how to do it more clever?

possible duplicate of VB.NET class inherits a base class and implements an interface issue (works in C#) — AakashM
– AakashM, Commented Jan 6, 2012 at 9:34

Hans Passant · Accepted Answer · 2012-01-06 13:24:10Z

1

Yes, not supported in vb.net. The compiler requires the interface to be implemented with an explicit Implements keyword, unlike C#. The closest you could get is:

Interface ICA
    Property NumberA() As Integer
End Interface
Interface ICB
    Property NumberB() As Integer
End Interface

Class A
    Implements ICA
    Public Property NumberA() As Integer Implements ICA.NumberA
        '' etc
    End Property
End Class

Class B
    Inherits A
    Implements ICA, ICB

    Public Property NumberB() As Integer Implements ICB.NumberB
        '' etc...
    End Property
End Class

Note that B now no longer needs to implement NumberA even though it implements ICA, the implementation in A is accepted. But of course that requires way too much tinkering with the original definitions. The workaround you used is good and has no detrimental effects at runtime. Note that you can make A1 private.

edited Jan 6, 2012 at 13:24

answered Jan 6, 2012 at 10:06

Hans Passant

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1 Comment

Lukas Pirkl Over a year ago

This is best solution. And when ICB interface inherits ICA, then everything is perfect.

Felix C · Accepted Answer · 2012-01-06 09:47:02Z

0

You can force to shadow the old property from your class with the Keyword 'Shadows'.

So maybe this is okay for you:

Public Class A

    Public Property NumberA As Integer

End Class

Public Class B
    Inherits A
    Implements I

    Public Shadows Property NumberA As Integer Implements I.NumberA
        Get
            Return MyBase.NumberA
        End Get
        Set(ByVal value As Integer)
            MyBase.NumberA = value
        End Set
    End Property

    Public Property NumberB As Integer Implements I.NumberB

End Class

Interface I
    Property NumberA As Integer
    Property NumberB As Integer
End Interface

answered Jan 6, 2012 at 9:47

Felix C

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Comments

Olivier Jacot-Descombes · Accepted Answer · 2012-01-06 15:17:57Z

You could also have a second interface that inherits from the first:

Interface IA
    Property NumberA() As Integer
End Interface

Interface IB
    Inherits IA

    Property NumberB() As Integer
End Interface

Class A
    Implements IA

    Public Property NumberA() As Integer Implements IA.NumberA
        Get
            Return m_NumberA
        End Get
        Set(ByVal value As Integer)
            m_NumberA = value
        End Set
    End Property
    Private m_NumberA As Integer
End Class

Class B
    Inherits A
    Implements IB

    Public Property NumberB() As Integer Implements IB.NumberB
        Get
            Return m_NumberB
        End Get
        Set(ByVal value As Integer)
            m_NumberB = value
        End Set
    End Property
    Private m_NumberB As Integer
End Class

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