public Annotation Annotation { get; }

Public ReadOnly Property Annotation As Annotation

void chartControl1_AnnotationRepositoryChanged(object sender, AnnotationRepositoryChangedEventArgs e) {
  AnnotationRepositoryChange lastChange = e.Change;
  Annotation myAnnotation = e.Annotation;
  //Add your logic here. 
}

Private Sub chartControl1_AnnotationRepositoryChanged(ByVal sender As Object, ByVal e As AnnotationRepositoryChangedEventArgs)
  Dim lastChange As AnnotationRepositoryChange = e.Change
  Dim myAnnotation As Annotation = e.Annotation
  'Add your logic here. 
End Sub