private void CommandBinding_ChangeBookExecuted(object sender, ExecutedRoutedEventArgs e)
        {
            Book book = this.booksDataGrid.SelectedItem as Book;

            book.IsNew = false;
            var bookWindow = new NewBook(book);

            bookWindow.ShowDialog();
            this.booksDataGrid.Items.Refresh();
        }
        private void CommandBinding_NewBookExecuted(object sender, ExecutedRoutedEventArgs e)
        {
            var curAuth    = (Author)this.authorsListView.SelectedItem;
            var book       = new Book();
            var bookWindow = new NewBook(book);

            if ((bool)bookWindow.ShowDialog())
            {
                curAuth.Books.Add(book);
            }
        }