private void txtTimKiem_TextChanged(object sender, TextChangedEventArgs e)
        {
            DataTable dataTable = new DataTable();

            if (txtTimKiem.Text.Length >= 1 && txtTimKiem.Text != "Tìm Kiếm...")
            {
                switch (type_timkiem)
                {
                case 0:
                {
                    dataTable = NguoiDungBUS.TimTheoMaND(txtTimKiem.Text.ToString());
                }
                break;

                case 1:
                {
                    dataTable = NguoiDungBUS.TimTheoHoTenNguoiDung(txtTimKiem.Text.ToString());
                }
                break;
                }
            }
            else if (txtTimKiem.Text.Length == 0)
            {
                dataTable = NguoiDungBUS.LoadDSND();
            }
            Load_Data(dataTable);
        }