Public Sub MainWindow_Loaded(ByVal sender As Object, ByVal e As _
  System.Windows.RoutedEventArgs) Handles Me.Loaded
'maincanvas heißt mein Canvas
Dim ellipse as new Ellipse
ellipse.Fill = Brushes.Red
ellipse.Width = 100
ellipse.Height = 100
Canvas.SetTop(ellipse, 150)
Canvas.SetLeft(ellipse, 150)
maincanvas.Children.Add(ellipse)

    Public Sub MainWindow_MouseDown(ByVal sender As Object, ByVal e As _
      System.Windows.Input.MouseButtonEventArgs) Handles Me.MouseDown
        pt = Mouse.GetPosition(maincanvas)
        Dim result As HitTestResult = VisualTreeHelper.HitTest(ellipse, pt)
        If result IsNot Nothing Then MsgBox("HIT!")
    End Sub