Visual Basic

<DllImport("ReaderDll")> _<br />
Public Function Read(ByVal strbData as StringBuilder) as Integer<br />
End Function

Dim a As New Point(0, 10)<br />
Dim b As New Point(1, 10)<br />
Dim c As New Point(0, 10)<br />
If a.Equals(b) Then Debug.WriteLine(" a  = b") Else Debug.WriteLine(" a not = b")<br />
If a.Equals(c) Then Debug.WriteLine(" a  = b") Else Debug.WriteLine(" a not = b")

' 2D POINT ===========================================================
Public Class POINT2
    'Friend _X As Decimal = Nothing   ' Remove the "= Nothing"'s.  Decimals are value types that
    'Friend _Y As Decimal = Nothing   ' can't be set to Nothing.  Also, you might want to change
                                      ' these to Doubles instead.  Decimal types are 128-bit numbers
                                      ' and a rather slow to work with.
    Friend _X As Double
    Friend _Y As Double
 
    Public Sub New(ByVal x As Double, ByVal y As Double)
        'mybase.new()                 ' Since this class isn't inheriting from anything (well, not really true!),
                                      ' you're calling the New of System.Object, which doesn't
                                      ' do anything.  Remove this line.
        'Me._X = x                    ' You should be setting your initial values using your
        'Me._Y = y                    ' Property statements.  Your Properties can validate the data
                                      ' and return Exceptions if not valid.
        Me.X = x
        Me.Y = y
    End Sub ' Constructor
 
    Public Property X() As Double     ' It doesn't hurt to be specific about what your coding.
        Get                           ' Making assumptions and not specifying exactly what you
            Return Me._X              ' want Public/Private can lead to hard to find problems.
        End Get
        Set(ByVal value)
            ' You might want to do some checking of your values to see if they
            ' are valid before setting the value of this class instance.
            Me._X = value
        End Set
    End Property ' Get/Set X
 
    Public Property Y() As Double
        Get
            Return Me._Y
        End Get
        Set(ByVal value)
            ' You might want to do some checking of your values to see if they
            ' are valid before setting the value of this class instance.
            Me._Y = value
        End Set
    End Property ' Get/Set Y
 
    Public Sub add(ByRef p1 As POINT2)    ' Remove the Overridable modifier.  You won't need it
        Me.X += p1.X                      ' since your not actually replacing the functionality
        Me.Y += p1.Y                      ' of POINT2, just adding another version of 'Add" to it.
    End Sub
End Class ' 2D POINT Class

' 3D POINT ===========================================================
Public Class POINT3
    Inherits POINT2
 
    Friend _Z As Double
 
    Public Sub New(ByVal x As Decimal, ByVal y As Decimal, ByVal z As Decimal)
        'MyBase.New(x, y)                 ' This line isn't required because you're setting all
                                          ' three values in this constructor.  Anything you do in
                                          ' in the POINT2 constructor would just be overwritten
                                          ' by what you have in this one.
        Me.X = x                          ' Again, go through the Properties!
        Me.Y = y
        Me.Z = z
    End Sub ' Constructor
 
    Public Property Z() As Double
        Get
            Return Me._Z
        End Get
        Set(ByVal value)
            Me._Z = value
        End Set
    End Property ' Get/Set Z
 
    Public Overloads Sub add(ByRef p1 As POINT3)  'Use Overloads here because you adding another
        Me.X += p1.X                      ' version of 'Add' to the base class that takes a
        Me.Y += p1.Y                      ' different parameter from what the base class version does.
        Me.Z += p1.Z                      ' Also, do your math using the Property versions of the
                                          ' fields.  You can check the values of the results of the
                                          ' math much easier this way.
    End Sub
End Class ' 3D Point

Public Sub New(ByVal x As Decimal, ByVal y As Decimal, ByVal z As Decimal)
    'MyBase.New(x, y)                 ' This line isn't required because you're setting all
                                      ' three values in this constructor.  Anything you do in
                                      ' in the POINT2 constructor would just be overwritten
                                      ' by what you have in this one.
    Me.X = x                          ' Again, go through the Properties!
    Me.Y = y
    Me.Z = z
End Sub ' Constructor

Public Sub New(ByVal x As Double, ByVal y As Double, ByVal z As Double)
    MyBase.New(x, y)
    Me.Z = z
End Sub                             ' Constructor

<code>Public Type MyPoint
    x As Double
    y As Double
End Type

Public Type MyLine
    Head As MyPoint
    Tail As MyPoint
End Type

Public Sub DrawLine(aLine As MyLine, Canves As Form)
    Canves.Line (aLine.Head.x, aLine.Head.y)-(aLine.Tail.x, aLine.Tail.y)
End Sub

Public Sub DrawLine(aLine As MyLine, Canves As PictureBox)
    Canves.Line (aLine.Head.x, aLine.Head.y)-(aLine.Tail.x, aLine.Tail.y)
End Sub
</code>