var words = new[] { "the", "quick", "brown", "fox", "jumps" };

 var query = from word in words

                    select word.Substring(,);

 foreach (var word in query)

 {

     Console.WriteLine(word);

 }

 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);

 }

         static void Main(string[] args)

         {

             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();

         }

         class Bouquet

         {

             public List<string> Flowers { get; set; }

         }        

八、联接操作

九、分组数据

 var numbers = new List<int>() { , , , , , , , , ,  };

 IEnumerable<IGrouping<bool, int>> query = from number in numbers

                                                       group number by number %  == ;

 foreach (var group in query)

 {

     Console.WriteLine($"{(group.Key ? "偶数" : "基数")}：");

     foreach (var i in group)

     {

         Console.WriteLine(i);

     }

 }    

十、生成操作

十一、等值操作

十二、元素操作

　　元素操作从一个序列返回单个特定元素。

十三、转换数据类型

　　转换方法更改输入对象的类型。

　　LINQ 查询中的转换运算可用于各种应用程序。下面是一些示例：

　　（1）Enumerable.AsEnumerable<TSource> 方法可用于隐藏类型的标准查询运算符的自定义实现。

　　（2）Enumerable.OfType<TResult> 方法可用于启用非参数化集合以进行 LINQ 查询。

　　（3）Enumerable.ToArray<TSource>、Enumerable.ToDictionary<TSource, TKey>、Enumerable.ToList<TSource> 和 Enumerable.ToLookup<TSource, TKey> 方法可用于强制立即执行查询，而非推迟到枚举查询时。

　　示例：

         static void Main(string[] args)

         {

             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();

         }

         class Plant

         {

             public string Name { get; set; }

         }

         class CarnivorousPlant : Plant

         {

             public string TrapType { get; set; }

         }    

十四、串联操作

十五、聚合操作

传送门

　　入门：《走进 LINQ 的世界》

　　进阶：《LINQ 标准查询操作概述》（强烈推荐）

　　技巧：《Linq To Objects - 如何操作字符串》 和 《Linq To Objects - 如何操作文件目录》

【来源】部分图片摘自微软官方文档