Group options for Asp.Net DropDownList after PostBack it is

Question

Hi

Group options for Asp.Net DropDownList after PostBack ,it is not Displaying Selected Item..

Code link:

http://mpurna.blogspot.in/2012/01/group-options-for-aspnet-dropdownlist.html

after PostBack the page it selecting First ListItem Every time ..Not selected which i have selected ListItem..

how to display the selected item after postback also.

Thanks.