Always List box index is returns value Zero while moving from source listbox to destination

hi i am moving items between listboxes. Source listbox values are populating from DataBase SQL server. When I Select an item from Source listbox and click on add button, no matter which item i selected but moving Item with index=0 only to souce item.  
Suppose i selected alaska(Index=3) from source listbox, when i click on add button, alaska needs to move to destination. but  "Chennai"(Which is index zero) is moving to listbox2. Always moving first item irrespective of selected item. Please solve my problem.