WPF-Drawing Canvas Control

Imports System.Globalization

Public Class CanvasPoint
    Inherits FrameworkElement

    Implements System.ComponentModel.INotifyPropertyChanged

    ' Create a collection of child visual objects.
    Private _children As VisualCollection

#Region "Constructors"
    Public Sub New()
        _children = New VisualCollection(Me)
        _children.Add(CreateDrawingVisualCircle())

    End Sub

    Public Sub New(p_position As Point)
        PositionOnCanvas = p_position

        _children = New VisualCollection(Me)
        _children.Add(CreateDrawingVisualCircle())
    End Sub
#End Region

#Region "Properties"

    Private p_PositionOnCanvas As New Point
    Public Property PositionOnCanvas() As Point
        Get
            Return p_PositionOnCanvas
        End Get
        Set(ByVal value As Point)
            p_PositionOnCanvas = value
            INotifyChange("PositionOnCanvas")
        End Set
    End Property
#End Region

#Region "Overided properties"

    ' Provide a required override for the VisualChildrenCount property.
    Protected Overrides ReadOnly Property VisualChildrenCount() As Integer
        Get
            Return _children.Count
        End Get
    End Property

    ' Provide a required override for the GetVisualChild method.
    Protected Overrides Function GetVisualChild(ByVal index As Integer) As Visual
        If index < 0 OrElse index >= _children.Count Then
            Throw New ArgumentOutOfRangeException()
        End If

        Return _children(index)
    End Function

#End Region

#Region "Drawing"
    ' Create a DrawingVisual that contains a rectangle.
    Private Function CreateDrawingVisualCircle() As DrawingVisual
        Dim drawingVisual As New DrawingVisual()

        ' Retrieve the DrawingContext in order to create new drawing content.
        Dim drawingContext As DrawingContext = drawingVisual.RenderOpen()

        ' Create a circle and draw it in the DrawingContext.
        drawingContext.DrawEllipse(Brushes.Red, New Pen(Brushes.Red, 1.0), PositionOnCanvas, 4, 4)

        ' Persist the drawing content.
        drawingContext.Close()

        Return drawingVisual
    End Function

#End Region

#Region "Events"
    Public Sub INotifyChange(ByVal info As String)
        RaiseEvent PropertyChanged(Me, New System.ComponentModel.PropertyChangedEventArgs(info))
    End Sub

    Public Event PropertyChanged(sender As Object, e As System.ComponentModel.PropertyChangedEventArgs) Implements System.ComponentModel.INotifyPropertyChanged.PropertyChanged
#End Region

End Class