how to access the dropdownlist value data bonded through jqu

Question

Hi friends, I have multiple text boxes and one drop down. Itemcode Itemname Batch(drop down) BatchQty When I select itemname through web service and ajax call I am binding Itemcode value.after this I am doing ajax call to bind corresponding Batches to dropdownlist. Again on dropdown select change event(jquery) I am assigning Batch qty value.All are aspx controls. Now my problem is while inserting data into table the values are not coming in code behind(c#.net).dropdownlist.selectedItem.Text and TxtBatchquantity.Text values are null.how can I get the values for Insertion.