Kendo Refresh (DropDownList.refresh()) not working ERROR Not define

Im trying to refresh the Drop Down List after another DropDownList is Change But the Refresh() method is Undefined Error Is Promoting.There For I Tried the Read the DataSource again and it shows it loading but the data is still the same.Help to Solve this Issue please.

Code:

$("#DropDownList1").change(function () {
   custCode = $("#DropDownList1").val();

   $("#titles").data("kendoDropDownList").dataSource.read(); //shows list Loading But Same Data Is present .
   $("#titles").data("kendoDropDownList").refresh(); //NOT Working 

});