Absolute z-order (across several DataTemplates)

Question

Ive a ListBox with a Canvas ItemsPanel that displays 2 different types of objects: NodeVMs and LinkLineVMs (using a CompositeCollection). Each VM object has a DataTemplate:

Answer 1

Set your ZIndex index in ListBox.ItemContainerStyle instead of your DataTemplate.

The reason for this is that all items are wrapped in a ListBoxItem, so you need to set the ZIndex on the ListBoxItem instead of on the DataTemplate

<Style TargetType="{x:Type ListBoxItem}">
    <Setter Property="Canvas.ZIndex" 
            Value="{Binding Converter={StaticResource GetObjectZIndexConverter}}" />
</Style>

You'll need a converter that checks the typeof your databound object, and returns the correct ZIndex based on if it's a NodeVM or NetworkLinkVM.

This will only set the ZIndex for your DataTemplates, but once those are sorted out, you can set the ZIndex of NetworkLinkVM's internal Line and TextBlock