Dropdown boxes with conditions on c#

Question

Hai Friends,
    I m creating one small application in that i ve two dropdown boxes with conditions.
mode of travel and seat type.
if i choosed air ==> economy,
                     business ll display.
add ===>button
its working on c#
as the same added the details ll show on gridview when i m edit the value the drop down box not working.
do the need full