BackTerminal.frmBookAdd.buttonOK_Click C# (CSharp) Method

        private void buttonOK_Click(object sender, EventArgs e)
        {
            int quantity = (int)numericUpDown.Value;
            string libraryName = (string)comboBoxLibrary.SelectedItem;
            SqlConnection connection = Library.Connection.Instance();

            // 获取 category id
            string queryString = "SELECT id FROM dbo.library where name='" + libraryName + "';";
            SqlCommand command = new SqlCommand(queryString, connection);
            SqlDataReader reader = command.ExecuteReader();
            int libraryId = 1;
            while (reader.Read())
            {
                libraryId = (int)reader[0];
                Console.Out.WriteLine(libraryId);
            }
            reader.Close();

            // INSERT INTO dbo.particular_book
            for (int i = 0; i < quantity; i++)
            {
                string sql = "INSERT INTO dbo.particular_book (book_isbn, library_id)" +
                    "VALUES(@book_isbn, @library_id);";
                command = new SqlCommand(sql, connection);
                command.Parameters.AddWithValue("@book_isbn", ISBN);
                command.Parameters.AddWithValue("@library_id", libraryId);
                command.ExecuteNonQuery();
            }
            this.Close();
        }