class Program
    {
        static void Main(string[] args)
        {
            #region LINQ Select
            var words = new[] { "the", "quick", "brown", "fox", "jumps" };
            var query = 
                from word in words
                select word.Substring(0, 1);
            foreach (var word in query)
            {
                Console.WriteLine(word);
            }
            Console.Read();
            #endregion
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            #region LINQ SelectMany
            var phrases = new List<string>() { "an apple a day", "the quick brown fox" };
            var query = 
                from phrase in phrases
                    from word in phrase.Split(‘ ‘)
                    select word;
            foreach (var word in query)
            {
                Console.WriteLine(word);
            }
            Console.Read();
            #endregion
        }
    }

    /// <summary>
    /// 花束类
    /// </summary>
    class Bouquet
    {
        public List<string> Flowers { get; set; }
    }
    
    class Program
    {
        static void Main(string[] args)
        {
            #region LINQ Select和SelectMany比较
            var bouquets = new List<Bouquet>()
            {
                new Bouquet {Flowers = new List<string> {"sunflower", "daisy", "daffodil", "larkspur"}},
                new Bouquet {Flowers = new List<string> {"tulip", "rose", "orchid"}},
                new Bouquet {Flowers = new List<string> {"gladiolis", "lily", "snapdragon", "aster", "protea"}},
                new Bouquet {Flowers = new List<string> {"larkspur", "lilac", "iris", "dahlia"}}
            };

            IEnumerable<List<string>> query1 = bouquets.Select(bq => bq.Flowers);
            IEnumerable<string> query2 = bouquets.SelectMany(bq => bq.Flowers);

            Console.WriteLine("query1->Select():");
            foreach (IEnumerable<string> collection in query1)
            {
                foreach (var item in collection)
                {
                    Console.WriteLine(item);
                }
            }

            Console.WriteLine("\nquery2->SelectMany():");
            foreach (var item in query2)
            {
                Console.WriteLine(item);
            }

            Console.Read();
            #endregion
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            #region LINQ 分组数据
            var numbers = new List<int>() { 35, 44, 200, 84, 3987, 4, 199, 329, 446, 208 };
            IEnumerable<IGrouping<bool, int>> query = from number in numbers
                                                      group number by number % 2 == 0;
            foreach (var group in query)
            {
                Console.WriteLine($"{(group.Key ? "偶数" : "基数")}：");
                foreach (var item in group)
                {
                    Console.WriteLine(item);
                }
            }
            Console.Read();
            #endregion
        }
    }

    /// <summary>
    /// 植物类
    /// </summary>
    class Plant
    {
        public string Name { get; set; }
    }

    /// <summary>
    /// 食肉植物类
    /// </summary>
    class CarnivorousPlant : Plant
    {
        public string TrapType { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            #region LINQ 转换数据类型
            var plants = new Plant[]
            {
                new CarnivorousPlant {Name = "Venus Fly Trap", TrapType = "Snap Trap"},
                new CarnivorousPlant {Name = "Pitcher Plant", TrapType = "Pitfall Trap"},
                new CarnivorousPlant {Name = "Sundew", TrapType = "Flypaper Trap"},
                new CarnivorousPlant {Name = "Waterwheel Plant", TrapType = "Snap Trap"}
            };
            var query = from CarnivorousPlant plant in plants
                        where plant.TrapType == "Snap Trap"
                        select plant;
            foreach (var carnivorousPlant in query)
            {
                Console.WriteLine(carnivorousPlant.Name);
            }
            Console.Read();
            #endregion
        }
    }