I have some code that looks like this:

<Expander Header="{Binding SelectedSlot.Name}"
          Visibility="{Binding ShowGroupSlot, Converter={StaticResource BooleanToVisibility}}">
    <Controls:GroupPrototypeSlotControl Slot="{Binding DataContext.SelectedSlot, 
        RelativeSource={RelativeSource Mode=FindAncestor,  AncestorType={x:Type Expander}}}" />
</Expander>

This works, but the ugliness of the Slot Binding bothers me. This is required because the GroupPrototypeSlotControl has a GroupPrototypeViewModel as its DataContext. If I simply use {Binding SelectedSlot}, it attempts to resolve it on the 'child' ViewModel, which fails. I get around this by explicitly looking at the DataContext of my parent control. Is there a cleaner way to do this type of binding?