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

        var columnName:String = event.dataField;
        var columnNumber:int  = event.columnIndex;
        var sortFields:Array;
        var sort:Sort;

        if (!sortableColumns || !columns[columnNumber].sortable)
            return;

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