Caliburn Micro with Treeview Context Menu - wpf

Question

I have my hierarchical treeview binding wonderfully to my ViewModel using Caliburn Micro. (The ViewModel has an Items property that returns an ObservableCollection - the treeview is named to this Items property - nothing wrong with the binding).
However the issue comes up with the context menu. The menu fires a method on an instance of the object that the treenode represents. What I rather want to achieve, is to have the menu fire a method on my root ViewModel, passing to it as a parameter the instance of the object represented by the clicked treenode.
Here is my XAML:
<HierarchicalDataTemplate DataType="{x:Type m:TaskGrouping}"
ItemsSource="{Binding Children}">
<Label Content="{Binding Name}"
FontWeight="Bold">
<Label.ContextMenu>
<ContextMenu>
<MenuItem Header="Add New SubFolder"
cal:Message.Attach="AddNewSubfolder" />
<MenuItem Header="Remove this folder"
cal:Message.Attach="RemoveFolder" />
</ContextMenu>
</Label.ContextMenu>
</Label>
</HierarchicalDataTemplate>
What changes do I need to make to my XAML in order to achieve what I want?

Answer 1

ContextMenus are located in a separate visual tree from everything else - it can be a pain to get the bindings right (I often have 10-15 minutes of fighting the bindings on them to get them right!)
You've got your Message.Attach attached property set, all you need to do is ensure that the action target is pointing to the VM rather than the data item. You can use Action.TargetWithoutContext to specify the target for actions (CM will otherwise use DataContext)
You will also need to get a binding path which points to the other visual tree - try using RelativeSource bindings - the ContextMenu also has a property called PlacementTarget which should point to the element that the ContextMenu is attached to
So possibly:
cal:Action.TargetWithoutContext="{Binding DataContext, RelativeSource={RelativeSource AncestorType=Label}}"
or
cal:Action.TargetWithoutContext="{Binding PlacementTarget.DataContext}"
You might have to experiment as I often get this almost right first time!
EDIT by OP(Shawn):
This is what worked for me eventually:
<Label Content="{Binding Name}"
Tag="{Binding DataContext, ElementName=LayoutRoot}">
<Label.ContextMenu>
<ContextMenu
cal:Action.TargetWithoutContext="{Binding PlacementTarget.Tag, RelativeSource={RelativeSource Self}}">
<MenuItem Header="Run Task Now" cal:Message.Attach="SomeRootViewModelMethod($dataContext)" />