I created a treeview in WPF MVVM with a hierarchical DAtaTemplate property.

Outside of the Treeview, I have an "EDIT" button. On press of edit button I want to pass the Treeview's selectedItem to the RelayCommand in the viewmodel.

I am implementing the same functionality within the TreeviewItem on double click of the node. However I want to know what is the best way to accomplish this outside.

My code structure is as follows

MainView -> MainViewModel

StateViewItem -> StateViewModel (HierarchicalDataTemplate inheriting from TreeViewItemViewModel)

RegionViewItem -> RegionViewModel (DataTemplate inheriting from TreeViewItemViewModel)

The RegionViewModel handles the double click for the node and accomplishes the Edit functionality.

However the "EDIT" button is outside of the treeview, how do I pass the selected RegionViewItem to the Command bound so I can load it for editing? 

thanks in advance for help