protected void ddlLoaiPhong_SelectedIndexChanged(object sender, EventArgs e)
{
ddlSoNguoi.DataSource = xl.LoadSN(ddlLoaiPhong.SelectedValue.ToString().Trim());
ddlSoNguoi.DataValueField = "SoNguoi";
ddlSoNguoi.DataTextField = "SoNguoi";
ddlSoNguoi.DataBind();
}