Redirect problem in Page

Hello Friends,
   I have a problem in redirect a page.i m using C#.net 2005 .i hv a dropdown list which is bind data from database Like State when i m selecting an item in dropdownlist then the corrospondin District should be come in the second dropdownlist. butit never comes.. there is a problem comes"The specified URL can not be found" I m writing the code below for beter understand.
I m also set the Autopostback property =true in dropdownlist.

 protected void Page_Load(object sender, EventArgs e)
    {
        if(!IsPostBack)
        {
            con.Open();
            SqlCommand com = new SqlCommand("select State from StateInfo order by StateName asc", con);
            dr = com.ExecuteReader();
            while (dr.Read() == true)
            {
                drp_regionname.Items.Add(dr[0].ToString());
            }
            dr.Close();
            
    }
}


 protected void drp_regionname_SelectedIndexChanged(object sender, EventArgs e)
    {
         
           
            string RegionName = drp_regionname.SelectedValue.ToString();
            SqlCommand com1 = new SqlCommand("select district from DistrictInfo  where StateName ='" + RegionName + "'", con);
            con.Open();
            dr = com1.ExecuteReader();
            while (dr.Read())
            {
                drp_unitname.Items.Add(dr[0].ToString());
            }
            dr.Close();
            con.Close();
        
    }

This code is running fine in local server but not running in Remote server..

Plz help me.......

Thanks ...