What I want to do is FreezableCollection.AddRange(collectionToAdd)

Question

What I want to do is FreezableCollection.AddRange(collectionToAdd)

Each time I add to the FreezableCollection an event is raised and something happens. Now I have a new collection I would want to add but this time I want the CollectionChanged event of the FreezableCollection to fire only once.

Looping through and adding them will raise the event for each new item.

Is there a way I can add to FreezableCollection all at a goal, similar to List.AddRange?

Answer 1

Derive from a collection and override the behavior that you'd like to change. I was able to do it this way:

public class PrestoObservableCollection<T> : ObservableCollection<T>
    {
        private bool _delayOnCollectionChangedNotification { get; set; }

        /// <summary>
        /// Add a range of IEnumerable items to the observable collection and optionally delay notification until the operation is complete.
        /// </summary>
        /// <param name="itemsToAdd"></param>
        public void AddRange(IEnumerable<T> itemsToAdd)
        {
            if (itemsToAdd == null) throw new ArgumentNullException("itemsToAdd");

            if (itemsToAdd.Any() == false) { return; }  // Nothing to add.

            _delayOnCollectionChangedNotification = true;            

            try
            {
                foreach (T item in itemsToAdd) { this.Add(item); }
            }
            finally
            {
                ResetNotificationAndFireChangedEvent();
            }
        }

        /// <summary>
        /// Clear the items in the ObservableCollection and optionally delay notification until the operation is complete.
        /// </summary>
        public void ClearItemsAndNotifyChangeOnlyWhenDone()
        {
            try
            {
                if (!this.Any()) { return; }  // Nothing available to remove.

                _delayOnCollectionChangedNotification = true;

                this.Clear();
            }
            finally
            {
                ResetNotificationAndFireChangedEvent();
            }
        }

        /// <summary>
        /// Override the virtual OnCollectionChanged() method on the ObservableCollection class.
        /// </summary>
        /// <param name="e">Event arguments</param>
        protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
        {
            if (_delayOnCollectionChangedNotification) { return; }

            base.OnCollectionChanged(e);
        }

        private void ResetNotificationAndFireChangedEvent()
        {
            // Turn delay notification off and call the OnCollectionChanged() method and tell it we had a change in the collection.
            _delayOnCollectionChangedNotification = false;
            this.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
        }
    }

Answer 2

To follow up @BobHorn's nice answer, to make it works with FreezableCollection,

from document:

This member is an explicit interface member implementation. It can be used only when the FreezableCollection instance is cast to an INotifyCollectionChanged interface.

So you can do that with a cast.

(FreezableCollection as INotifyCollectionChanged).CollectionChanged += OnCollectionChanged;