Hi Fabien,
Thanks for using Syncfusion products.
ActiveDocumentChanged event will raise, whenever a document selected in DocumentContainer. And DocumentClosing event will fire, whenever you a closed a document in DocumentContainer.
We have attached a simple sample which using these events.
http://www.syncfusion.com/uploads/redirect.aspx?&team=support&file=DocumentContainerEventsDemo1300564470.zipLet us know if you have any other queries.
Thanks,
Karthikeyan