How to Avoid Firing ObservableCollection.CollectionChanged Multiple Times When Replacing All Elements Or Adding a Collection of Elements

I have ObservableCollection<T> collection, and I want to replace all elements with a new collection of elements, I could do:

collection.Clear(); 

OR:

collection.ClearItems();

(BTW, what's the difference between these two methods?)

I could also use foreach to collection.Add one by one, but this will fire multiple times

Same when adding a collection of elements.

EDIT:

I found a good library here: Enhanced ObservableCollection with ability to delay or disable notifications but it seems that it does NOT support silverlight.