asp.net drop down list dont get updated

Hi everybody.I am trying to write a web page where i have to select an item form a drop down list.
I am using linq to sql to get the data from the database.the strange thing is that i can register the data to the drop down list but when i select one of them the drop down list lets me to the first item. I set post back = true because i want to update the page every time an item get selected. I wrote a really simple code to check what was going wrong but still...no success. Below i am bringing the code i wrote. If someone could help me that would be really nice.


.aspx


<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="WebApplication7.WebForm1" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns=& ...