protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { dtKhachHang dt1 = new dtKhachHang(); DataTable da1 = dt1.LayDanhSachKhachHang_InBaoCao(); da1.Rows.Add(-1, "Tất cả khách hàng"); ccbKhachHang.DataSource = da1; ccbKhachHang.TextField = "TenKhachHang"; ccbKhachHang.ValueField = "ID"; ccbKhachHang.DataBind(); ccbKhachHang.SelectedIndex = da1.Rows.Count; } }