I'm creating a "ColorMap Canvas", i.e. a canvas where clicking the Canvas will return the color of the corresponding picture. (I'm actually adapting Atheist's PictureBox_ColorMap control for use with a Canvas)

I've got the following code:
Code:
Protected Overrides Sub OnMouseMove(ByVal e As MouseButtonEventArgs)
   Dim p As System.Windows.Point = e.GetPosition(Me)
   MyBase.OnMouseMove(e)
   If _RaiseEventOnMouseMove Then
      If Not _ColorMap Is Nothing AndAlso p.X <= _ColorMap.Width AndAlso p.Y <= _ColorMap.Height Then
         RaiseEvent ColorMapMouseMove(Me, _ColorMap.GetPixel(CInt(p.X), CInt(p.Y)))
      Else
         RaiseEvent ColorMapMouseMove(Me, Nothing)
      End If
   End If
End Sub
The IDE gives me the error:
"sub 'OnMouseMove' cannot be declared 'Overrides' because it does not override a sub in a base class."

When I remove the keyword "Overrides" I get the error:
"sub 'OnMouseMove' shadows an overridable method in the base class 'UIElement'. To override the base method, this method must be declared 'Overrides'."

What's going on here? Why can't I override OnMouseMove? Is my IDE suffering from schizophrenia?