Define Blend Expression ViewModel definition for RelativeSource binding - wpf

Question

I have an UserControl (MyCompositeView) where I add some other UserControls (MyDetailView). To get intellisense and refactoring ability I add to the CompositeView the d:DataContext in xaml.
To Manipulate the UserControl while adding them an new DataContext I bind the Visiblity to the RelativeSource (my CompositeViewModel). Unfortunately the matching against the MyCompositeViewModel isn't working for this Binding in the Editor.
Is there a way to let visual studio know that my DataContext of DataContext.DetailsIsVisible is from the type MyCompositeViewModel?
<UserControl
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
x:Class="Example.MyCompositeView"
d:DataContext="{d:DesignInstance Type=MyCompositeViewModel}"
d:DesignHeight="300"
d:DesignWidth="300"
mc:Ignorable="d">
<Grid>
<detail:MyDetailView
DataContext="{Binding Path=DetailViewModel}"
Visibility="{Binding RelativeSource={RelativeSource FindAncestor,
AncestorType={x:Type UserControl}},
Path=DataContext.DetailsIsVisible,
Converter={StaticResource BooleanToVisibilty}}" />
</Grid>
</UserControl>
--
public class MyCompositeViewModel : IMyCompositeViewModel {
public bool DetailisVisible{get;set;}
public MyDetailViewModel DetailViewModel { get; }
}

Answer 1

Try binding by element name instead:
<UserControl
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
x:Class="Example.MyCompositeView"
x:Name="root"
d:DataContext="{d:DesignInstance Type=MyCompositeViewModel}"
d:DesignHeight="300"
d:DesignWidth="300"
mc:Ignorable="d">
<Grid>
<detail:MyDetailView
DataContext="{Binding Path=DetailViewModel}"
Visibility="{Binding ElementName="root"},
Path=DataContext.DetailsIsVisible,
Converter={StaticResource BooleanToVisibilty}}" />
</Grid>
</UserControl>
or flip the property order:
<UserControl
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
x:Class="Example.MyCompositeView"
d:DataContext="{d:DesignInstance Type=MyCompositeViewModel}"
d:DesignHeight="300"
d:DesignWidth="300"
mc:Ignorable="d">
<Grid>
<detail:MyDetailView
Visibility="{Binding DetailsIsVisible, Converter={StaticResource BooleanToVisibilty}}"
DataContext="{Binding DetailViewModel}"/>
</Grid>
</UserControl>