列表框控件（SelectionMode = Multiple）是否无法在sql-server中加载所有数据？

Question

我有一个表'TheLoai'，我想从SQL-Server加载它，但是它不能有效地工作。

        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                getData();
            }
        }

        public void getData()
        {
            SqlConnection conn = new SqlConnection(@"Data Source=DESKTOP-R8LG380\SQLEXPRESS;Initial Catalog=PHIM;Integrated Security=True");

            SqlCommand cmd = new SqlCommand("select * from TheLoai", conn);
            conn.Open();
            SqlDataReader dtr = cmd.ExecuteReader();
            lst_TheLoai.DataSource = dtr;
            lst_TheLoai.DataTextField = "TenTL";
            lst_TheLoai.DataValueField = "MaTL";
            lst_TheLoai.DataBind();
            conn.Close();

        }