SupressCollectionEvents.cs

public static class ObservableCollectionExtensions
{
   public static IDisposable SuppressCollectionEvents(this INotifyCollectionChanged collection,
           bool fireEventWhenComplete = true)
   {
       return new CollectionEventSuppressor(collection, fireEventWhenComplete);
   }

   private class CollectionEventSuppressor : IDisposable
   {
       private readonly INotifyCollectionChanged _collection;
       private readonly bool _raiseEventWhenComplete;
       private readonly NotifyCollectionChangedEventHandler _currentListeners;
       private readonly Type _type;
       private readonly FieldInfo _eventField;

       public CollectionEventSuppressor(INotifyCollectionChanged collection, bool raiseEventWhenComplete)
       {
           _collection = collection;
           _raiseEventWhenComplete = raiseEventWhenComplete;
           _type = collection.GetType();
           _eventField = _type.GetField("CollectionChanged", BindingFlags.Instance | BindingFlags.NonPublic);
           if (_eventField == null)
               throw new TypeLoadException("Could not find CollectionChanged event on " + _type.FullName);
           _currentListeners = GetListeners();
           ClearListeners();
       }

       public void Dispose()
       {
           RestoreListeners();
           if (_raiseEventWhenComplete && _currentListeners != null)
           {
               RaiseEvent();
           }
       }

       private NotifyCollectionChangedEventHandler GetListeners()
       {
           return _eventField.GetValue(_collection) as NotifyCollectionChangedEventHandler;
       }

       private void ClearListeners()
       {
           SetListeners(null);
       }

       private void RestoreListeners()
       {
           SetListeners(_currentListeners);
       }

       private void SetListeners(NotifyCollectionChangedEventHandler listeners)
       {
           _eventField.SetValue(_collection, listeners);
       }

       private void RaiseEvent()
       {
           var eventArgs = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset, null);
           _currentListeners(_collection, eventArgs);
       }
   }
}