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

Question

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.

Answer 1

ColinE is right with all his informations. I only want to add my subclass of ObservableCollection that I use for this specific case.

public class SmartCollection<T> : ObservableCollection<T> {     public SmartCollection()         : base() {     }      public SmartCollection(IEnumerable<T> collection)         : base(collection) {     }      public SmartCollection(List<T> list)         : base(list) {     }      public void AddRange(IEnumerable<T> range) {         foreach (var item in range) {             Items.Add(item);         }          this.OnPropertyChanged(new PropertyChangedEventArgs("Count"));         this.OnPropertyChanged(new PropertyChangedEventArgs("Item[]"));         this.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));     }      public void Reset(IEnumerable<T> range) {         this.Items.Clear();          AddRange(range);     } } 

Answer 2

You can achieve this by subclassing ObservableCollection and implementing your own ReplaceAll method. The implementation of this methods would replace all the items within the internal Items property, then fire a CollectionChanged event. Likewise, you can add an AddRange method. For an implementation of this, see the answer to this question:

ObservableCollection Doesn't support AddRange method, so I get notified for each item added, besides what about INotifyCollectionChanging?

The difference between Collection.Clear and Collection.ClearItems is that Clear is a public API method, whereas ClearItems is protected, it is an extension point that allows your to extend / modify the behaviour of Clear.