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