Linq善解人意之通过MSDN对14个“查询关键字“逐个解剖

Posted 2020-09-02

linq中存在的 14个关键字

网址: https://msdn.microsoft.com/zh-cn/library/bb310804.aspx

from: 迭代变量

where：对数据源进行逻辑筛选

select：对数据进行塑形。

group： 分组

into： 分组链接

orderby[ascending/descending]: 排序

join：表关联

let：就是局部变量

string[] strings =
{
"A penny saved is a penny earned.",
"The early bird catches the worm.",
"The pen is mightier than the sword."
};

// Split the sentence into an array of words
// and select those whose first letter is a vowel.
var earlyBirdQuery =
from sentence in strings
let words = sentence.Split(‘ ‘)
from word in words
let w = word.ToLower()
where w[0] == ‘a‘ || w[0] == ‘e‘
|| w[0] == ‘i‘ || w[0] == ‘o‘
|| w[0] == ‘u‘
select word;

foreach (var sentence in strings)
{
var words = sentence.Split(‘ ‘);

foreach (var word in words)
{
var w = word.ToLower();

if (w[0] == ‘a‘ || w[0] == ‘e‘|| w[0] == ‘i‘ || w[0] == ‘o‘|| w[0] == ‘u‘)
{
// List.Add(word);
}
}
}

这些查询表达式 源自于 sql。。。这样方便我们去快速的写出代码，而且也不失可读性。

好一点的文章：

linq可以嵌套，太复杂也不容易看得懂