可枚举对象操作

        class Product
        {
            public int ID { get; set; }
            public string Name { get; set; }
            public string Region { get; set; }
            public decimal Price { get; set; }
            public bool IsFavorite { get; set; }
        }

void testIEnumerable()
        {
            List<Product> products = new List<Product> {
                new Product { ID=1, Name="路易十八比萨饼", Region="意大利", Price=79961, IsFavorite = false },
                new Product { ID=2, Name="澳洲胡桃", Region="澳洲", Price=195, IsFavorite = false },
                new Product { ID=3, Name="Almas鱼子酱", Region="伊朗", Price=129950, IsFavorite = false },
                new Product { ID=4, Name="和牛肉", Region="日本", Price=3250, IsFavorite = true },
                new Product { ID=5, Name="麝香猫咖啡豆", Region="印尼", Price=2000, IsFavorite = true },
                new Product { ID=6, Name="大红袍茶叶", Region="中国", Price=208000, IsFavorite = true },
                new Product { ID=7, Name="Kona Nigari矿泉水", Region="美国", Price=13000, IsFavorite = true },
                new Product { ID=8, Name="Diva伏特加", Region="北欧", Price=6500, IsFavorite = false },
                new Product { ID=9, Name="番红花的雄蕊", Region="地中海", Price=38986, IsFavorite = false },
            };
            bool allChina = products.All(p => p.Region == "中国");
            bool anyChina = products.Any(p => p.Region == "中国");
            int count = products.Count(p => p.ID > 5);
            decimal max = products.Max(p => p.Price);
            int minid = products.Min(p => p.ID);
            decimal avg = products.Average(p => p.Price);
            decimal sum = products.Sum(p => p.Price);
            Product agg = products.Aggregate((total, next) => { total.Price += next.Price; return total; });

            string[] select1 = products.Select(p => p.Name).ToArray();
            var select2 = products.Select(p => new { p.ID, p.Name }).ToDictionary(d => d.ID);
            var selectMore = products.Select(p => new { p.ID, p.Name, p.Price }).ToList();
            var lookup = products.ToLookup(l => l.IsFavorite, p => new { p.ID, p.Name, p.Region, p.Price }).ToList();
            lookup.ForEach(l =>
            {
                Console.WriteLine(l.Key ? "己收" : "未收");
                l.ToList().ForEach(item => Console.WriteLine("\t{0}\t{1}\t{2}\t{3}", item.ID, item.Name, item.Region, item.Price));
            });

            var rightorder = products.OrderBy(p => p.IsFavorite).ThenByDescending(p => p.ID).ToList();
            var group = products.GroupBy(p => p.IsFavorite).Select(g => new { IsFavorite = g.Key, SumPrice = g.Sum(item => item.Price), CountItem = g.Count() }).ToList();
            group.ForEach(g => Console.WriteLine("{0}\t{1}\t{2}", g.IsFavorite, g.SumPrice, g.CountItem));
            //Linq语法
            var grouping = (from p in products
                            group p by p.IsFavorite
                            into g
                            select new { IsFavorite = g.Key, SumPrice = g.Sum(item => item.Price), CountItem = g.Count() }
                            ).ToList();

            var ps = (from p in products where p.ID > 4 select new { ID = p.ID, Name = p.Name, Price = p.Price }).ToList();
            foreach (var item in ps)
            {
                Console.WriteLine("\t{0}\t{1}\t{2}", item.ID, item.Name, item.Price);
            }

            var distinct = products.Distinct().ToList();//去重
            var take = products.Take(3).ToList(); //从头取3条记录
            var takewhile = products.TakeWhile(p => p.ID <= 4).ToList(); //从头取记录，满足条件继续，遇到不满足条件停止
            var skip = products.Skip(3).ToList();   //跳过开头3条记录
            var skipwhile = products.SkipWhile(p => p.Price < 10000).ToList(); //当满足条件就跳过，遇到不满足条件就取剩下所有记录
            var contains = products.Where(p => p.Name.Contains("红")).ToList(); //Name中包含”红"字
            var first = products.Where(p => p.Name.StartsWith("大")).First(); //Name大开头的记录的第一条。无记录报异常
        }