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;
}
}