C# LINQ学习笔记二：LINQ标准查询操作概述

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

    classProgram
    {
        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 inphrases
                    from word in phrase.Split(' ')
                    selectword;
            foreach (var word inquery)
            {
                Console.WriteLine(word);
            }
            Console.Read();
            #endregion}
    }

    /// <summary>
    ///花束类
    /// </summary>
    classBouquet
    {
        public List<string> Flowers { get; set; }
    }
    
    classProgram
    {
        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 inquery1)
            {
                foreach (var item incollection)
                {
                    Console.WriteLine(item);
                }
            }

            Console.WriteLine("query2->SelectMany():");
            foreach (var item inquery2)
            {
                Console.WriteLine(item);
            }

            Console.Read();
            #endregion}
    }

    classProgram
    {
        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 innumbers
                                                      group number by number % 2 == 0;
            foreach (var group inquery)
            {
                Console.WriteLine($"{(group.Key ? "偶数": "基数")}：");
                foreach (var item ingroup)
                {
                    Console.WriteLine(item);
                }
            }
            Console.Read();
            #endregion}
    }

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

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

    classProgram
    {
        static void Main(string[] args)
        {
            #region LINQ 转换数据类型
            var plants = newPlant[]
            {
                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 inplants
                        where plant.TrapType == "Snap Trap"
                        selectplant;
            foreach (var carnivorousPlant inquery)
            {
                Console.WriteLine(carnivorousPlant.Name);
            }
            Console.Read();
            #endregion}
    }