internal void ProcessDelta()
{
if (added.Count > 0)
{
var list = new CollectionChangedEventArgs <T>(added);
added.Clear();
Added.RaiseAsync(list);
}
if (removed.Count > 0)
{
var list = new CollectionChangedEventArgs <T>(removed);
removed.Clear();
Removed.RaiseAsync(list);
}
}