Is there a ContentPane IsActive property? I need to know from within the content pane when it is activated.
There is an IsActivePane property on the ContentPane. I'm not sure what you mean by knowing from within the ContentPane. You would have to go up to the ancestor (i.e. containing) ContentPane element and check this property. The active pane is tied to the element with keyboard focus so you could assume that if your element contained the keyboard focus that it was the active pane.
I needed to be able to hide and show contextual menu items base on which pane is active, and remove the menu items for the inactive panes. I solved this using the visualtreehelper and finding its parent host and using the ActiveDocumentChanged event.