Hi Arif,
Thank you for your interest in Syncfusion Products.
Please refer the below link for online sample which illustrates the working of MultiColumnDropDownCombo using UpdatePanel and the sample files can be downloaded from 'Download source'.
http://websamples.syncfusion.com/samples/Tools.Web/6.4.0.15/78452-MultiColumnDropDownCombo/main.htmPlease let me know if this sample helps you or I misunderstood the query.
Thanks,
Rekha