private void next_step(object sender, RoutedEventArgs e)
        {
            books pr = (books)grid.SelectedItem;

            if (pr != null)
            {
                string id_product = pr.idBook;
                this.Visibility = Visibility.Hidden;

                new Student(connection, this, id_product);
            }
        }
        public TakeBook(SqlConnection connection, Window parent)
        {
            InitializeComponent();
            this.Show();
            parent.Visibility = Visibility.Hidden;
            this.connection   = connection;
            this.parent       = parent;
            try
            {
                List <books>  book_list     = new List <books>();
                string        sqlexpression = "SELECT CodeBook, NameBook, YearPublic, Photo FROM dbo.BOOKS";
                SqlCommand    command       = new SqlCommand(sqlexpression, connection);
                SqlDataReader reader        = command.ExecuteReader();
                if (reader.HasRows)
                {
                    while (reader.Read())
                    {
                        books rec = new books();
                        rec.idBook    = reader.GetValue(0).ToString();
                        rec.titleBook = reader.GetValue(1).ToString();
                        rec.Year      = reader.GetValue(2).ToString();
                        rec.photo     = reader[3] as byte[];

                        book_list.Add(rec);
                    }

                    reader.Close();
                    grid.ItemsSource = book_list;
                }
                else
                {
                    reader.Close();
                }
            }
            catch (SqlException er)
            {
                MessageBox.Show(er.Message);
            }
        }