private void dgvDanhSachKhachHang_RowEnter(object sender, DataGridViewCellEventArgs e)
{
txtMaKhachHang.Text = dgvDanhSachKhachHang.Rows[e.RowIndex].Cells[0].FormattedValue.ToString();
txtTenKhachHang.Text = dgvDanhSachKhachHang.Rows[e.RowIndex].Cells[1].FormattedValue.ToString();
txtSoDienThoai.Text = dgvDanhSachKhachHang.Rows[e.RowIndex].Cells[3].FormattedValue.ToString();
txtDiaChi.Text = dgvDanhSachKhachHang.Rows[e.RowIndex].Cells[2].FormattedValue.ToString();
txtCongNo.Text = dgvDanhSachKhachHang.Rows[e.RowIndex].Cells[4].FormattedValue.ToString();
chitietkhachhang = hoadonController.SearchMaKhachHang(int.Parse(txtMaKhachHang.Text));
dgvDanhSachHoaDon.DataSource = chitietkhachhang;
}