为什么DropDownList 取的值总是默认值

 在我调试的时候总是取不到选中的下拉列表的值，大家看看是什么原因啊！！！提交的总是默认的值public partial class admin01_add : System.Web.UI.Page
{
 static string adminName;
    private string ConnectionString = ConfigurationManager.ConnectionStrings["adminConString"].ToString();
    private void InitializeComponent()
    {
        this.Load += new System.EventHandler(this.Page_Load);
    }   
    protected void Page_Load(object sender, EventArgs e)
    {
        if (Session.IsNewSession == false || Session["adminName"] != null)
        {
            if (!Page.IsPostBack)
            { 
                    if ((Convert.ToInt32(Session["level"].ToString()) == 3 && Convert.ToInt32(Session["class"].ToString()) == 1) || (Convert.ToInt32(Session["level"].ToString()) == 5))
                    {
                        adminName = Session["adminName"].ToString();
                        TextBox1.Focus();
                        getDropdrowList();
                        //DropDownList2.Items.Insert(0,new ListItem("请选择地区",""));
                    }
                    else
                    {
                        Response.Redirect("error.html");
                    }          
            }
        }
        else
        {
            Response.Redirect("login.aspx");
        }      
    }
    private void getDropdrowList()
    {
        adminDataBase db = new adminDataBase();
        DropDownList2.DataSource = db.GetDS("select lo_id, area from jq_location where class = 1 order by area asc");
        DropDownList2.DataValueField = "lo_id";
        DropDownList2.DataTextField = "area";
        DropDownList2.DataBind();
        db.SqlConnectionClose();
        DropDownList2.SelectedIndex = 0;
    }
    //提交按钮
    protected void Button1_Click(object sender, EventArgs e)
    {
        try
        {            
                DateTime datetime = new System.DateTime();
                datetime = System.DateTime.Now;
                SqlConnection con = new SqlConnection(ConnectionString);
                con.Open();
                string sql;
                DropDownList2.ClearSelection();
                DropDownList1.ClearSelection();
                sql = "insert into jq_it(co_id,co_name,co_shortname,co_passwd,co_product_1,co_product_2,co_product_3,co_product_other,co_deputy,co_tel,co_deputy_1,co_tels,co_tel_1,co_tel_2,co_fax,co_email_1,co_email_2,co_web,co_adress,co_location,co_info,co_hide) values('" + this.TextBox1.Text.ToUpper() + "','" + this.TextBox2.Text.ToString().Trim() + "','" + this.TextBox17.Text.ToString().Trim() + "','" + this.TextBox3.Text.ToString() + "','" + this.TextBox4.Text.ToString().Trim() + "','" + this.TextBox5.Text.ToString().Trim() + "','" + this.TextBox6.Text.ToString().Trim() + "','" + this.TextBox7.Text.ToString().Trim() + "','" + this.TextBox8.Text.ToString().Trim() + "','" + this.TextBox9.Text.ToString().Trim() + "','" + this.TextBox10.Text.ToString().Trim() + "','" + this.TextBox19.Text.ToString().Trim() + "','" + this.TextBox20.Text.ToString().Trim() + "','" + this.TextBox11.Text.ToString().Trim() + "','" + this.TextBox12.Text.ToString().Trim() + "','" + this.TextBox13.Text.ToString().Trim() + "','" + this.TextBox14.Text.ToString().Trim() + "','" + this.TextBox15.Text.ToString().Trim() + "','" + this.TextBox16.Text.ToString().Trim() + "','" + this.DropDownList2.SelectedValue.ToString().Trim() + "','" + this.TextBox18.Text.ToString().Trim() + "'," + Convert.ToInt32(DropDownList1.SelectedValue) + ")"; 
               SqlCommand com = new SqlCommand(sql, con);
                com.ExecuteReader();
                adminDataBase db = new adminDataBase();
                int l = db.Log(Session["adminName"].ToString(),"IT添加会员");
                Response.Write("<script> alert ('添加成功')</script>");
                this.TextBox1.Text = "";
                this.TextBox1.Focus();
                this.TextBox2.Text = "";
                this.TextBox3.Text = "";
                this.TextBox4.Text = "";
                this.TextBox5.Text = "";
                this.TextBox6.Text = "";
                this.TextBox7.Text = "";
                this.TextBox8.Text = "";
                this.TextBox9.Text = "";
                this.TextBox10.Text = "";
                this.TextBox11.Text = "";
                this.TextBox12.Text = "";
                this.TextBox13.Text = "";
                this.TextBox14.Text = "";
                this.TextBox15.Text = "";
                this.TextBox16.Text = "";
                this.TextBox17.Text = "";
                this.TextBox18.Text = "";
                this.TextBox19.Text = "";
                this.TextBox20.Text = "";
                txtRepasswd.Text = "";
            }
            catch (Exception s)
            {
                Response.Write("<script> alert ('" + s.Message.ToString() + "') </script>");
            }
    }