          if (!collection.sort || !collection.sort.fields)
          {
              singleColumnSort = true;
-             var sort:Sort = new Sort();
+             var sort:ISort = new Sort();
              sort.fields = [];
              
              collection.sort = sort;

        }

        column.sortDescending = desc;
        var field:SortField = new SortField(columnName); // name
        field.descending = desc;
        
//        field.name = column.dataField;

        }

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