private void bt_ok_Click(object sender, EventArgs e)
        {
            string sign   = cb_qx.SelectedItem.ToString();
            string id     = tb_Id.Text;
            string name   = tb_name.Text;
            string passwd = tb_passwd.Text;

            if (sign.Equals("学生"))
            {
                bool result = DAO_Student.UpdataStudentPasswd(name, passwd);
                if (result)
                {
                    MessageBox.Show("修改成功");
                }
                else
                {
                    MessageBox.Show("修改失败,请重试");
                }
            }
            else
            {
                string teaSex       = "";
                string teaDuties    = "";
                string teaTelephone = "";
                bool   result       = DAO_Teacher.UpdataTeaInfo(id, name, teaSex, teaDuties, teaTelephone, passwd);
                if (result)
                {
                    MessageBox.Show("修改成功");
                }
                else
                {
                    MessageBox.Show("修改失败,请重试");
                }
            }
        }
        private void add_button_Click(object sender, EventArgs e)
        {
            string teaId        = tb_stuId.Text;
            string teaName      = tb_teaName.Text;
            string teaSex       = cb_TeaSex.Text;
            string teaTelephone = tb_TeaTelephone.Text;
            string teaDuties    = cb_TeaDuties.Text;
            string passwd       = "";
            bool   result       = DAO_Teacher.UpdataTeaInfo(teaId.Trim(), teaName.Trim(), teaSex.Trim(), teaDuties.Trim(), teaTelephone.Trim(), passwd);

            if (result)
            {
                MessageBox.Show("修改成功");
            }
            else
            {
                MessageBox.Show("修改失败,请重试");
            }
        }