private void OnDataSourcesChanged(IEnumerable <IDataSourceViewModel> oldValue,
IEnumerable <IDataSourceViewModel> newValue)
{
var old = oldValue as INotifyCollectionChanged;
if (old != null)
{
old.CollectionChanged -= ItemsSourceOnCollectionChanged;
}
FilteredItemsSource.Clear();
if (newValue != null)
{
foreach (IDataSourceViewModel model in newValue)
{
if (PassesFilter(model))
{
FilteredItemsSource.Add(model);
}
}
var @new = newValue as INotifyCollectionChanged;
if (@new != null)
{
@new.CollectionChanged += ItemsSourceOnCollectionChanged;
}
}
}
private void ItemsSourceOnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
{
switch (e.Action)
{
case NotifyCollectionChangedAction.Add:
for (var i = 0; i < e.NewItems.Count; ++i)
{
var model = (IDataSourceViewModel)e.NewItems[i];
if (PassesFilter(model))
{
var sourceIndex = e.NewStartingIndex + i;
var filteredIndex = FindFilteredIndex(sourceIndex);
FilteredItemsSource.Insert(filteredIndex, model);
}
}
break;
case NotifyCollectionChangedAction.Remove:
foreach (IDataSourceViewModel model in e.OldItems)
{
FilteredItemsSource.Remove(model);
}
break;
case NotifyCollectionChangedAction.Reset:
FilteredItemsSource.Clear();
break;
default:
throw new NotImplementedException();
}
UpdateNoDataSourcesMessage();
}