CompositeAnnotationViewModel issue

Hi,

CompositeAnnotation works perfectly and easy to use, but I need it in MVVM. CompositeAnnotationViewModel looks the same, but it is not visible. This is my code:

AnnotationViewModels.Add(new CompositeAnnotationViewModel()
{
    Annotations = new ObservableCollection<IAnnotationViewModel>()
    {
        new VerticalLineAnnotationViewModel
        {
            VerticalAlignment = VerticalAlignment.Stretch,
            Stroke = Colors.Blue,
            StrokeThickness = 2,
            IsEditable = true,
            StrokeDashArray = new DoubleCollection() { 2, 2 },
            CoordinateMode = AnnotationCoordinateMode.Relative,
            X1 = 0
        },
        new VerticalLineAnnotationViewModel
        {
            VerticalAlignment = VerticalAlignment.Stretch,
            Stroke = Colors.Blue,
            StrokeThickness = 2,
            IsEditable = true,
            StrokeDashArray = new DoubleCollection() { 2, 2 },
            CoordinateMode = AnnotationCoordinateMode.Relative,
            X1 = 1
        }
    },
    IsEditable = true,
    X1 = 3,
    X2 = 5
});

What is my mistake?