我做的一个修改密码的功能代码如下   
protected void ImageButton1_Click(object sender, ImageClickEventArgs e)
    {
        //连接数据库
        OracleConnection conn = new OracleConnection("Data Source = JXTCMI ; user = system ;password = manager");
        string oldpwd = tb_oldpwd.Text;
        try
        {
            conn.Open();
            OracleCommand cmd = conn.CreateCommand();
            string sid = Convert.ToString(HttpContext.Current.Session["sId"]);
            cmd.CommandText = "select password from login where id ='" + sid + "'";
            OracleDataReader odr = cmd.ExecuteReader();
            if (odr.Read())
            {
                if (odr["password"].ToString() == oldpwd)
                {
                   OracleCommand updateCmd = conn.CreateCommand();
                   updateCmd.CommandText = "update login set password = '"+ oldpwd+"' where id = '"+ sid +"'";
                   updateCmd.ExecuteNonQuery();
                   Response.Write("<script>alert('修改成功!');</script>");
                }
                else
                {                    Response.Write("<script>alert('旧密码输入错误,请重新输入!');</script>");
                 }
                conn.Close();
            }
            else
            {
                Response.Write("<script>alert('登陆超时,请重新登录!');</script>");
                Response.Redirect(@"../../login.aspx");
            }
            
            conn.Close();
        }
        catch (Exception ex)
        {
            Response.Write(ex.Message); //如果有错误,输出错误信息
        }
        finally
        {
            conn.Close(); //关闭连接
        }
    }运行没有报错,但是数据库中的数据却没有变,这是怎么回事啊?