Annotation visibility MVVM

I hate to revive an old thread; however, today I found myself in a scenario where I was trying to use a DataTrigger to define whether my annotation would be visible or not. I was using the Visibility property and despite using the DataTrigger correctly it didn’t work. I found that I had to use the “IsHidden” property of the Annotation for my DataTrigger to work. I find this relevant to anyone who faces the same problem I did. Although there is a Visibility property for this element, it doesn’t respond to the value of this property. With irony, it will respond if you apply the same logic outside of a data trigger and use simple binding in the XAML which declares the annotation like this below. However, it is a good practice to avoid properties like “Visibility” within a ViewModel.

<s:LineAnnotation Visibility="{Binding Path=MyLineVisibility}" />

See snippet from my XAML for a LineAnnotation that worked the way I preferred.

<s:LineAnnotation Stroke="Purple" 
                                     X1="{Binding Path=FiftyLineX1}" 
                                     X2="{Binding Path=FiftyLineX2}" 
                                     Y1="{Binding Path=FiftyLineField}" 
                                     Y2="{Binding Path=FiftyLineField}">
                <s:LineAnnotation.Style>
                    <Style TargetType="{x:Type s:LineAnnotation}">
                        <Setter Property="IsHidden" Value="True" />
                        <Style.Triggers>
                            <DataTrigger Binding="{Binding Path=MeasurementExists, UpdateSourceTrigger=PropertyChanged}" Value="True">
                                <Setter Property="IsHidden" Value="False" />
                            </DataTrigger>
                        </Style.Triggers>
                    </Style>
                </s:LineAnnotation.Style>
            </s:LineAnnotation>

There’s no easy way to do this other than ‘Foreach annotation in Annotations where YAxisId = …’.

I was going to suggest a default style, but since AnnotationBase.YAxis is not a dependency property you can’t bind AnnotationBase.IsHidden directly to YAxis.Visibility.

Maybe you could do it with an element name binding from AnnotationBase.IsHidden to YAxis.Visibility but it wouldn’t be clean or easy. I think stick with what you have!