         // do the sort if we're allowed to
         if (c.sortable)
         {
-            var s:Sort = collection.sort;
-            var f:SortField;
+            var s:ISort = collection.sort;
+            var f:ISortField;
             if (s)
             {
                 s.compareFunction = null;

            return;

        var view:ICollectionView = ICollectionView(dataProvider);
        var sort:Sort = view.sort;
        if (!sort)
        {
            sortIndex = lastSortIndex = -1;

        }

        // fields.length == 1, so the collection is sorted on a single field.
        var sortField:ISortField = fields[0];
        var n:int = _columns.length;
        sortIndex = -1;
        for (var i:int = 0; i < n; i++)
