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

Question

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

collection.Cl         


        

Answer 1

For the past few years I am using a more generic solution to eliminate too many ObservableCollection notifications by creating a batch change operation and notifying observers with a Reset action:

public class ExtendedObservableCollection: ObservableCollection
{
    public ExtendedObservableCollection()
    {
    }

    public ExtendedObservableCollection(IEnumerable items)
        : base(items)
    {
    }

    public void Execute(Action> itemsAction)
    {
        itemsAction(Items);
        OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
    }
}

Using it is straightforward:

var collection = new ExtendedObservableCollection(new[]
{
    "Test",
    "Items",
    "Here"
});
collection.Execute(items => {
    items.RemoveAt(1);
    items.Insert(1, "Elements");
    items.Add("and there");
});

Calling Execute will generate a single notification but with a drawback - list will be updated in UI as a whole, not only modified elements. This makes it perfect for items.Clear() followed by items.AddRange(newItems).