private IVirtualChangeSet <TObject, TKey> Virtualise(ISortedChangeSet <TObject, TKey> updates = null)
{
if (_isLoaded == false)
{
return(null);
}
var previous = _current;
var virualised = _all.Skip(_parameters.StartIndex)
.Take(_parameters.Size)
.ToList();
_current = new KeyValueCollection <TObject, TKey>(virualised, _all.Comparer, updates?.SortedItems.SortReason ?? SortReason.DataChanged, _all.Optimisations);
////check for changes within the current virtualised page. Notify if there have been changes or if the overall count has changed
var notifications = _changedCalculator.Calculate(_current, previous, updates);
if (notifications.Count == 0 && (previous.Count != _current.Count))
{
return(null);
}
var response = new VirtualResponse(_parameters.Size, _parameters.StartIndex, _all.Count);
return(new VirtualChangeSet <TObject, TKey>(notifications, _current, response));
}
private VirtualChangeSet()
{
SortedItems = new KeyValueCollection <TObject, TKey>();
Response = new VirtualResponse(0, 0, 0);
}
