private void LvTaiLieu_SelectionChanged(object sender, SelectionChangedEventArgs e)
 {
     if (e.AddedItems.Count == 0)
     {
         return;
     }
     else
     {
         TaiLieu tl = e.AddedItems[0] as TaiLieu;
         txtTenTaiLieu.Text = tl.tenTaiLieu;
         txtMaTaiLieu.Text  = tl.maTaiLieu;
         cmbTheLoai.Text    = tl.theLoai;
         if (cmbTheLoai.Text == "Sách")
         {
             Sach sach1 = e.AddedItems[0] as Sach;
             txtTenTacGia.Text = sach1.tenTacGia;
             txtSoTrang.Text   = sach1.soTrang;
         }
         if (cmbTheLoai.Text == "Tạp chí")
         {
             TapChi tc1 = e.AddedItems[0] as TapChi;
             txtChuDe.Text = tc1.chuDe;
             txtGia.Text   = tc1.Gia.ToString();
         }
     }
 }
        private void BtnXoa_Click_1(object sender, RoutedEventArgs e)
        {
            if (lvTaiLieu.SelectedItems == null)
            {
                MessageBox.Show("Bạn chưa chọn nội dung để xóa", "CHỌN NỘI DUNG", MessageBoxButton.OK);
            }
            else
            {
                MessageBoxResult ret = MessageBox.Show("Bạn muốn xóa ?", "Hỏi xóa ", MessageBoxButton.YesNo, MessageBoxImage.Question);
                if (ret == MessageBoxResult.No)
                {
                    return;
                }
                else
                {
                    foreach (TaiLieu tailieu in lvTaiLieu.SelectedItems)
                    {
                        if (tailieu.theLoai == "Tạp chí")
                        {
                            TaiLieu tai = new TapChi();
                            tai = tailieu;
                            var tapchi = (TapChi)tai;
                            tapChiList.Remove(tapchi);
                        }
                        if (tailieu.theLoai == "Sách")
                        {
                            TaiLieu tai1 = new Sach();
                            tai1 = tailieu;
                            var sach = (Sach)tai1;
                            sachList.Remove(sach);
                        }

                        taiLieuList.RemoveAt(taiLieuList.IndexOf(tailieu));
                    }
                    lvTaiLieu.Items.Clear();
                    foreach (TaiLieu tailieu in taiLieuList)
                    {
                        lvTaiLieu.Items.Add(tailieu);
                    }
                }
            }
        }
        private void btnLuu_Click(object sender, RoutedEventArgs e)
        {
            bool conLoi = false;

            #region Kiểm tra nhập vào
            if (string.IsNullOrEmpty(txtMaTaiLieu.Text))
            {
                ChuaNhapMaTaiLieu.Visibility = Visibility.Visible;
                conLoi = true;
            }
            else
            {
                foreach (TaiLieu tai in taiLieuList.ToList())
                {
                    if (txtMaTaiLieu.Text == tai.maTaiLieu)
                    {
                        if (cmbTheLoai.SelectedIndex == 0)
                        {
                            Sach sach = new Sach();
                            sach.maTaiLieu    = txtMaTaiLieu.Text;
                            sach.tenTaiLieu   = txtTenTaiLieu.Text;
                            sach.ngayPhatHanh = dtpNgayPhatHanh.SelectedDate.Value;
                            sach.tenTacGia    = txtTenTacGia.Text;
                            sach.soTrang      = txtSoTrang.Text;
                            sach.theLoai      = cmbTheLoai.Text;
                            TaiLieu tai1 = new Sach();
                            tai1 = tai;
                            var sachthe = (Sach)tai1;
                            sachList[sachList.IndexOf(sachthe)]   = sach;
                            taiLieuList[taiLieuList.IndexOf(tai)] = sach;
                        }
                        else if (cmbTheLoai.SelectedIndex == 1)
                        {
                            TapChi tapChi = new TapChi();
                            tapChi.maTaiLieu    = txtMaTaiLieu.Text;
                            tapChi.tenTaiLieu   = txtTenTaiLieu.Text;
                            tapChi.ngayPhatHanh = dtpNgayPhatHanh.SelectedDate.Value;
                            tapChi.theLoai      = cmbTheLoai.Text;
                            tapChi.chuDe        = txtChuDe.Text;
                            tapChi.Gia          = Convert.ToDouble(txtGia.Text);
                            TaiLieu tai1 = new TapChi();
                            tai1 = tai;
                            var tapchithe = (TapChi)tai1;
                            tapChiList[tapChiList.IndexOf(tapchithe)] = tapChi;
                            taiLieuList[taiLieuList.IndexOf(tai)]     = tapChi;
                        }
                        #region Xoa
                        txtMaTaiLieu.Clear();
                        txtTenTacGia.Clear();
                        txtTenTacGia.Clear();
                        txtSoTrang.Clear();
                        txtTenTaiLieu.Clear();
                        txtChuDe.Clear();
                        txtGia.Clear();
                        dtpNgayPhatHanh.SelectedDate = null;
                        cmbTheLoai.SelectedIndex     = -1;
                        txtMaTaiLieu.Focus();
                        #endregion
                    }
                }
            }
            if (string.IsNullOrEmpty(txtTenTaiLieu.Text))
            {
                ChuaNhapMaTaiLieu.Visibility = Visibility.Visible;
                conLoi = true;
            }
            if (dtpNgayPhatHanh.SelectedDate == null)
            {
                ChuaChonNgayPhatHanh.Visibility = Visibility.Visible;
                conLoi = true;
            }
            if (cmbTheLoai.SelectedIndex == -1)
            {
                ChuaChonTheLoai.Visibility = Visibility.Visible;
                conLoi = true;
            }
            if (cmbTheLoai.SelectedIndex == 0)
            {
                if (string.IsNullOrEmpty(txtTenTacGia.Text))
                {
                    ChuaNhapTenTacGia.Visibility = Visibility.Visible;
                    conLoi = true;
                }
                if (string.IsNullOrEmpty(txtSoTrang.Text))
                {
                    ChuaNhapSoTrang.Visibility = Visibility.Visible;
                    conLoi = true;
                }
            }
            else if (cmbTheLoai.SelectedIndex == 1)
            {
                if (string.IsNullOrEmpty(txtChuDe.Text))
                {
                    ChuaNhapChuDe.Visibility = Visibility.Visible;
                    conLoi = true;
                }
                if (string.IsNullOrEmpty(txtGia.Text))
                {
                    ChuaNhapGia.Visibility = Visibility.Visible;
                    conLoi = true;
                }
            }
            #endregion
            if (!conLoi)
            {
                lvTaiLieu.Items.Clear();
                if (cmbTheLoai.SelectedIndex == 0)
                {
                    Sach sach = new Sach();
                    sach.maTaiLieu    = txtMaTaiLieu.Text;
                    sach.tenTaiLieu   = txtTenTaiLieu.Text;
                    sach.ngayPhatHanh = dtpNgayPhatHanh.SelectedDate.Value;
                    sach.tenTacGia    = txtTenTacGia.Text;
                    sach.soTrang      = txtSoTrang.Text;
                    sach.theLoai      = cmbTheLoai.Text;
                    sachList.Add(sach);
                    taiLieuList.Add(sach);
                }
                else if (cmbTheLoai.SelectedIndex == 1)
                {
                    TapChi tapChi = new TapChi();
                    tapChi.maTaiLieu    = txtMaTaiLieu.Text;
                    tapChi.tenTaiLieu   = txtTenTaiLieu.Text;
                    tapChi.ngayPhatHanh = dtpNgayPhatHanh.SelectedDate.Value;
                    tapChi.theLoai      = cmbTheLoai.Text;
                    tapChi.chuDe        = txtChuDe.Text;
                    tapChi.Gia          = Convert.ToDouble(txtGia.Text);
                    tapChiList.Add(tapChi);
                    taiLieuList.Add(tapChi);
                }
                txtMaTaiLieu.Clear();
                txtTenTacGia.Clear();
                txtTenTacGia.Clear();
                txtSoTrang.Clear();
                txtTenTaiLieu.Clear();
                txtChuDe.Clear();
                txtGia.Clear();
                dtpNgayPhatHanh.SelectedDate = null;
                cmbTheLoai.SelectedIndex     = -1;
                txtMaTaiLieu.Focus();
            }
            foreach (TaiLieu taiLieu in taiLieuList)
            {
                lvTaiLieu.Items.Add(taiLieu);
            }
        }