ThisDocument_BeforeSave with multiple word documents - events

Question

I have added a document before save to a Word plugin within the Application Document Change event handler:
private void Application_DocumentChange()
{
Microsoft.Office.Tools.Word.Document vstoDocument = Globals.Factory.GetVstoObject(this.Application.ActiveDocument);
vstoDocument.BeforeSave += ThisDocument_BeforeSave;
}
I have included the Before save event handler within the document change in the hopes that it would be applied to every word document which is opened.
This works very nicely when only having one word document open. However, when a second document is opened and then the first document is closed, the action does not fire on save.
However, as long as the first document remains open, the save action triggers on all other documents nicely.
Basically, it appears that the event handler only seems to be applied to the first opened document and ceases to work when that document is closed.
Cheers

Answer 1

You need to declare the source object at the global to prevent it from swiping by the Garbage Collector (GC). When GC collects the heap your source object can be destroyed and you will not get any events at all.
Microsoft.Office.Tools.Word.Document vstoDocument = null;
private void Application_DocumentChange()
{
vstoDocument = Globals.Factory.GetVstoObject(this.Application.ActiveDocument);
vstoDocument.BeforeSave += ThisDocument_BeforeSave;
}