I have a listbox and a dropdownlist on a asp.net web form.
when the user selects an item in the listbox, it goes to another page, which is fine.
If you go back to the page with the listbox and select an item from the dropdownlist, the listbox selectedindexchanged event is fired instead of the dropdownlist selectedindexchanged event.

What can i do to prevent this?

When you say "go back," are you using the browser's back button?
If not you may want to set the SelectedIndex back to 0 in the page_load. Or you could test if the dropdownlist SelectedIndex has changed in the listbox SelectedIndexChanged event. It sounds like the listbox event is firing because it come first on the page.

-Hunter

Yes, if i use the browser's back button.
Is there a way to set the listbox.selctedindex to -1 if you use the browser's back button.

Or is there a way to prevent the listbox to fire before the dropdownlist

Can you show us your codes?

Maybe a moderator will correct me if I'm wrong, but I'm fairly sure there is nothing you can do to the page when you use the back button. The browser doesn't reload the page when you press back, it just recalls it from the cache.
Its always best to try to avoid use of the back button with forms. Are you linking to your own pages? You could provide a link to navigate back to the page with the listbox and dropdownlist.

-Hunter

the actual problem is when an item is selected in the listbox, the listbox selectedindexchanged evnet fires when i clicked on the dropdownlist, i want the dropdownlist selectedindexchanged event to fire.

I know it is because an item in the listbox is selected, but how can i ignore the selected item in the listbox and fire the the selectedindexchanged event of the dropdownlist instead