private void updateBookList() { lbBooks.Items.Clear(); if (lbAuthor.SelectedItem == null || authorChkBox.Checked == false) { foreach (Book element in _bookService.All()) { if (element.copies.Exists(b => b.Loan.Equals(false)) || availChkBox.Checked == false) { if ((element.Title.ToLower()).Contains(searchField.Text.ToLower()) || (element.author.Name.ToLower()).Contains(searchField.Text.ToLower())) { lbBooks.Items.Add(element); } } } } if (lbAuthor.SelectedItem != null && authorChkBox.Checked == true) { foreach (Book element in _bookService.ByAuthor((Author)lbAuthor.SelectedItem)) { if (element.copies.Exists(b => b.Loan.Equals(false)) || availChkBox.Checked == false) { if ((element.Title.ToLower()).Contains(searchField.Text.ToLower()) || (element.author.Name.ToLower()).Contains(searchField.Text.ToLower())) { lbBooks.Items.Add(element); } } } } updateBookInfo(); }