How do you implement Page_Load event. Could I have your Page_Load code? Thank you!

I actually don’t have any page_load code, because I don’t want any action until use request an action.

    }

I found the Problem!!!

 seems like a funny one. I'd try recreating the drop down list in a new content page, and maybe try to output the selected value to a label, just to make sure the autopostback and selectedindex changed works properly