http://blogs.msdn.com/b/davbr/archive/2011/12/29/when-is-it-safe-to-use-objectids.aspxAs mentioned in this post , ObjectIDs are really pointers to managed objects on the GC heap. And as you know, objects get collected or move around on the heap during GCs. So how do you safely work with ObjectIDs? The overall guidance is that if youen-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)