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:

static void Linq1()
{
    int[] numbers = { 5, 3, 2, 4, 0, 7, 8, 6, 9, 1 };
    var numModBy3 = from n in numbers
                    group n by n % 3
                        into g
                        select new { Remainder = g.Key, Numbers = g };

    foreach (var g in numModBy3)
    {
        Console.Write("被3整除余 {0} : ", g.Remainder);
        foreach (var num in g.Numbers)
        {
            Console.Write("{0} ", num);
        }
        Console.WriteLine();
    }
}

例2：对单词按首字母分组

代码：

static void Linq2()
{
    string[] words = { "blueberry", "chimpanzee", "abacus", "banana", "apple", "cheese" };
    var groupedData = from w in words
                        group w by w[0]
                            into g
                            orderby g.Key // 加排序
                            select new { FirstChar = g.Key, Words = g };
    foreach (var g in groupedData)
    {
        Console.Write("以 {0} 字母开头的有 : ", g.FirstChar);
        foreach (var word in g.Words)
        {
            Console.Write("{0} ", word);
        }
        Console.WriteLine();
    }
}

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