onselectedindexchanged is not firing while using Keyboard

[Prasad]

I'm using the custom control to select a particular value from the drop down
using keyboard as suggested in
http://www.dotnetjohn.com/articles.aspx?articleid=132 and it worked .net 1.1
version. Recently we migrated the project from .net 2.0 after that
onselectedindexchanged event is not firing. User is able to select the
values required option for example if user wants "Brown" they can select the
same but after the selection event is not getting fired. The same code is
working fine if user changes the value by using mouse. Can you please help
me in fixing this issue? Thanks.