/// <summary>
/// When the sort or filter changes, creates or destroys the view
/// as needed.
///
/// This should only be called if a sort or filter is applied.
///
/// BUGBUG: what happens if there was a sort or filter, but they are being removed?
/// </summary>
void UpdateView()
{
if (view != null &&
model != null)
{
var temp = new DataStoreVirtualCollection <object>(model);
// filter if needed
var viewItems = (Filter != null) ? temp.Where(Filter).ToList() : temp.ToList();
// sort if needed
if (this.comparer != null)
{
viewItems.Sort(this.comparer);
}
// Clear and re-add the list
view.Clear();
view.AddRange(viewItems);
// If a sort or filter is specified, create a dictionary
// of the item indices. This materializes a list of all the
// objects.
// If no sort or filter is specified, this overhead is avoided.
viewToModel = null;
modelToView = null;
if (HasSortOrFilter)
{
viewToModel = new List <int>();
modelToView = new Dictionary <int, int>();
// Create a temporary dictionary of model items
var modelIndexes = new Dictionary <object, int>();
for (var i = 0; i < temp.Count; ++i)
{
var o = temp[i];
if (o != null)
{
modelIndexes[o] = i;
}
}
var viewIndex = 0;
foreach (var o in viewItems)
{
var modelIndex = -1;
if (o != null &&
modelIndexes.TryGetValue(o, out modelIndex))
{
modelToView[modelIndex] = viewIndex;
}
viewToModel.Add(modelIndex); // always add to viewToModel because the number of items must match those in viewItems
viewIndex++;
}
}
}
}
public DataStoreEnumerator(DataStoreVirtualCollection <T> collection)
{
this.collection = collection;
this.cursor = -1;
}
