public void DanhSachKhachHang()
{
dtKhachHang dtkh = new dtKhachHang();
ccbKhachHang.DataSource = dtkh.LayDanhSachKhachHangBanHang();
ccbKhachHang.TextField = "TenKhachHang";
ccbKhachHang.ValueField = "ID";
ccbKhachHang.DataBind();
}