How to Bind CommandParameter to Unknown Parent

Question

I have the following context menu declared in my application resources, and it is referenced by several tree views in my app. I am trying to send the TreeView's SelectedItem property as the command parameter.

The problem is that I can't figure out how to get the commands to send the TreeView's SelectedItem.

The parameter is always null. I have tried using relative sources, templated parents, etc.; as well as, looking for a target of treeview, treeviewitem, and simply the datacontext. I have also tried sending different properties of these items (not just the TreeView's SelectedItem). I can't seem to get it to resolve anything.

<Application.Resources>
    <ContextMenu x:Key="ContextMenu.TreeView">
        <MenuItem 
            Header="Add Node"
            Command="{Binding AddNodeCommand}"
            CommandParameter="{Binding Path=SelectedItem, RelativeSource={RelativeSource AncestorType={x:Type TreeView}}}"></MenuItem>
        <MenuItem
            Header="Delete Node"
            Command="{Binding DeleteNodeCommand}"
            CommandParameter="{Binding Path=SelectedItem,RelativeSource={RelativeSource AncestorType={x:Type TreeView}}}"></MenuItem>
    </ContextMenu>
</Application.Resources>

<UserControl ...>
    <TreeView 
        x:Name="TaxonomyTree"
        ItemsSource="{Binding Path=Tree}"        
        ContextMenu="{StaticResource ContextMenu.TreeView}"/>
</UserControl>

Answer 1

Try:

<ContextMenu x:Key="ContextMenu.TreeView">
  <MenuItem Command="{Binding AddNodeCommand}"
            CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor,
                                                                      AncestorType={x:Type ContextMenu}},
                                        Path=PlacementTarget.SelectedItem}"
            Header="Add Node" />
  <MenuItem Command="{Binding DeleteNodeCommand}"
            CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor,
                                                                      AncestorType={x:Type ContextMenu}},
                                        Path=PlacementTarget.SelectedItem}"
            Header="Delete Node" />
</ContextMenu>

Contextmenu is not part of the same Visual tree as the TreeView it links against. So we need to use the PlacementTarget to route to the TreeView accordingly.