public void RecalculateFilter()
{
if (Filter == null)
{
FilteredItems.ForEach(item => InternalAdd(item));
FilteredItems.Clear();
}
else
{
// Remove the items that no longer pass the filter
var itemsRemovedByNewFilter = new List <T>();
for (int i = BackingList.Count - 1; i >= 0; i--)
{
if (!PassesFilter(BackingList[i]))
{
itemsRemovedByNewFilter.Add(BackingList[i]);
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove, BackingList[i], i));
base.RemoveAt(i);
}
}
// Add the previously filtered items that that now pass
FilteredItems.RemoveWhere(item => {
var insertionIndex = InternalAdd(item);
if (insertionIndex >= 0)
{
OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, item, insertionIndex));
return(true);
}
return(false);
});
// Don't move items into the filtered list until it has been iterated over
FilteredItems.UnionWith(itemsRemovedByNewFilter);
}
}