Hello,
We kindly ask you to post your technical questions/problems in the support ticketing system (http://www.telerik.com/account/support-tickets/available-support-list.aspx) as this is the best way to reach our support staff - the support system assigns a response time for all of your questions, depending on your license and ensures that all questions will reach the respective developers, if needed. Alternatively, you can ask the community for help by posting your question in the online forums (http://www.telerik.com/community/forums.aspx). We try to monitor these requests as well, but we cannot guarantee they will be answered properly and in the expected timeframe.
Regards,
Telerik Team

Please note that the top list item is returned in the RadListBoxEventArgs just not the entire RadListBoxItem list.