private void BtnLuu_Click(object sender, RoutedEventArgs e)
        {
            if (txtSoLuong.Text == "")
            {
                MessageBox.Show("Bạn phải nhập số lượng!", "Lỗi!", MessageBoxButton.OK, MessageBoxImage.Error);
                txtSoLuong.Focus();
            }
            else
            {
                NguyenLieuController       nguyenLieu = new NguyenLieuController();
                ChiTietPhieuXuatCollection chitiet    = new ChiTietPhieuXuatCollection();
                chitiet.TenNL       = cbbTenNguyenLieu.Text;
                chitiet.SoLuongXuat = Convert.ToInt32(txtSoLuong.Text);
                chitiet.GhiChu      = txtGhiChu.Text;
                if (isEditing)
                {
                    ChiTietPhieuXuatCollection rm = dgvPhieuXuat.SelectedItem as ChiTietPhieuXuatCollection;
                    ctpx.Remove(rm);
                    isEditing = false;
                }
                ctpx.Add(chitiet);

                btnThem.IsEnabled = true;
                btnSua.IsEnabled  = true;
                btnXoa.IsEnabled  = true;
                btnLuu.IsEnabled  = false;
                btnHuy.IsEnabled  = false;

                cbbTenNguyenLieu.IsEnabled = false;
                txtSoLuong.IsEnabled       = false;
                txtGhiChu.IsEnabled        = false;

                dgvPhieuXuat.SelectedIndex = 0;
            }
        }
        private void DgvPhieuXuat_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            ChiTietPhieuXuatCollection chitiet = dgvPhieuXuat.SelectedItem as ChiTietPhieuXuatCollection;

            if (chitiet != null)
            {
                cbbTenNguyenLieu.SelectedItem = chitiet.TenNL;
                txtSoLuong.Text = chitiet.SoLuongXuat.ToString();
                txtGhiChu.Text  = chitiet.GhiChu;
            }
        }
        private void BtnXoa_Click(object sender, RoutedEventArgs e)
        {
            MessageBoxResult result = MessageBox.Show("Bạn có chắc muốn xóa nguyên liệu này?", "Xác nhận!", MessageBoxButton.OKCancel, MessageBoxImage.Question);

            if (result == MessageBoxResult.OK)
            {
                ChiTietPhieuXuatCollection rm = dgvPhieuXuat.SelectedItem as ChiTietPhieuXuatCollection;
                ctpx.Remove(rm);
            }

            dgvPhieuXuat.SelectedIndex = 0;
        }