LINQ 101——分组、Set、转换、Element

一、Grouping（分组）

例1：对于0-9数按被3整除的结果分组

代码:

 1 static void Linq1()
 2 {
 3     int[] numbers = { 5, 3, 2, 4, 0, 7, 8, 6, 9, 1 };
 4     var numModBy3 = from n in numbers
 5                     group n by n % 3
 6                         into g
 7                         select new { Remainder = g.Key, Numbers = g };
 8
 9     foreach (var g in numModBy3)
10     {
11         Console.Write("被3整除余 {0} : ", g.Remainder);
12         foreach (var num in g.Numbers)
13         {
14             Console.Write("{0} ", num);
15         }
16         Console.WriteLine();
17     }
18 }

例2：对单词按首字母分组

代码：

 1 static void Linq2()
 2 {
 3     string[] words = { "blueberry", "chimpanzee", "abacus", "banana", "apple", "cheese" };
 4     var groupedData = from w in words
 5                         group w by w[0]
 6                             into g
 7                             orderby g.Key // 加排序
 8                             select new { FirstChar = g.Key, Words = g };
 9     foreach (var g in groupedData)
10     {
11         Console.Write("以 {0} 字母开头的有 : ", g.FirstChar);
12         foreach (var word in g.Words)
13         {
14             Console.Write("{0} ", word);
15         }
16         Console.WriteLine();
17     }
18 }

二、Set(集合)

Distinct去重

source.Distinct();

其他 Union、Intersect、Except 参见 LINQ 101 Sample

三、Conversion（转换）

ToList
ToDictionary

四、Element（元素操作）

First
FirstOrDefault