FilteredList/SortedList

[Martin Sladecek]

On 01/18/2013 07:15 PM, Richard Bair wrote:
> I think using a ListBinding would work, in that we already pay attention both to the reference changing or the items changing. The main question will be around how sorting a ListBinding target works (does it update the source as well?). Particularly if the ListBinding is doing some filtering (or based on 5 source lists or something).

No, the bindings should not update the source, it's the same as with 
other bindings. The new value (new List in this case) is computed when 
the binding is evaluated, leaving the source untouched.

The reason why I don't like this idea is that we already know we need 
some additional methods for the index translation and TransformationList 
clearly states it is a wrapper around something.
While ListExpression (this is the right class to use in the API, not 
ListBinding) doesn't have to be a wrapper around anything. It might be a 
concatenation of 2 different lists or a per-element sum of 2 lists or 
maybe some list representing a tokenized String.
Putting index translation methods into ListExpression would be confusing 
and wouldn't fit into Bindings API much.

I would rather see some TransformationList to ListExpression conversion 
and leave TransformationList separate of bindings.

-Martin