private void newBookshelfToolStripMenuItem_Click(object sender, EventArgs e)
        {
            BookshelfWindow bookshelf = new BookshelfWindow(database);

            bookshelf.MdiParent = this;
            bookshelf.Show();
        }
        public BookshelfManager()
        {
            InitializeComponent();
            //create first view
            BookshelfWindow bookshelf = new BookshelfWindow(database);

            bookshelf.MdiParent = this;
            bookshelf.Show();
        }