/// <summary>
        /// ....各类书籍推荐...
        /// 
        /// 应当在此处呈现await的返回值...
        /// </summary>
        /// <param name="args"></param>
        static void Main(string[] args)
        {
            //第一类书籍：心理学....
            var book = new List<book>()
            {
                new book() { book_classify = "心理学", book_name = "每一种孤独都有陪伴" },
                new book() { book_classify = "心理学", book_name = "愿你拥有被爱照亮的生命" },
                new book() { book_classify = "心理学", book_name = "感谢自己的不完美" },
                new book() { book_classify = "编程语言", book_name = "编写高质量代码 改善C#程序的157个建议" },
                new book() { book_classify = "编程语言", book_name = "python cookbook" },
                new book() { book_classify = "编程语言", book_name = "设计模式（C#版）" }
            };

            //var test = book.Where(p => p.book_classify == "心理学").Select(p => p.book_name);

            //foreach(var i in test)
            //{
            //    Console.WriteLine(i);
            //}

            var task = handle(book);


            Console.WriteLine(task.Result);

        }

        /// <summary>
        /// Attention:
        /// 在这里取出我们通过Task任务放到线程池中处理并返回的数据，同时注意
        /// 除了传递异步调用方法(这里是 Phycology方法)之外，因为可能需要做其他的操作，
        /// 我们可以将await关键字放在异步调用方法返回的变量处，而不是直接使用await关键字去等待调用方法
        /// 这样设计充分利用了时间，提高了效率...
        /// </summary>
        /// <param name="book"></param>
        /// <returns></returns>
        public static async Task<string> handle(List<book> book)
        {
            var _physchology = Phycology(book);

            var _programmer = Programmer(book);

            ///在这里做一些其他的操作...
            ///以充分利用时间

            return await _physchology + await _programmer;

        }


        /// <summary>
        /// Attention:
        /// 应当将需要的数据返回到调用方法处...
        /// 在这里是  sb
        /// </summary>
        /// <param name="book"></param>
        /// <returns></returns>
        public static async Task<string> Programmer(List<book> book)
        {
            StringBuilder sb = new StringBuilder();

            return await Task.Run(() =>
            {
                var programmer = book.Where(p => p.book_classify == "编程语言").Select(p => p.book_name).ToList();

                foreach(var i in programmer)
                {
                    sb.Append(i + "\r\n");
                }

                return sb.ToString();
            });

        }

        public static async Task<string> Phycology(List<book> book)
        {
            StringBuilder sb = new StringBuilder();
            return await Task.Run(() =>
            {

                var _phychology = book.Where(p => p.book_classify == "心理学").Select(p => p.book_name).ToList();

                foreach(var i in _phychology)
                {
                    sb.Append(i + "\r\n");
                }

                return sb.ToString();
            });
        }

    }