前言

简单介绍一下linq 查询表达式。

正文

上文其实已经介绍了查询表达式了。

(资料图片)

但是呢，这里就介绍一些复杂一点的。

这里不会去介绍查询表达式，而是直接介绍一些复杂的。

let 字句。

static void Main(string[] args){var files = from fileName in Directory.EnumerateFiles("c://", "test")orderby new FileInfo(fileName).LastAccessTime, fileName descendingselect new FileInfo(fileName);}

这样写会new FileInfo两遍，如果使用let 那么就是一遍。

static void Main(string[] args){var files = from fileName in Directory.EnumerateFiles("c://", "test")let file = new FileInfo(fileName)orderby file.LastAccessTime, fileName descendingselect file;}

第二个是into:

连续查询。

就是一个查询字句，作为第二个查询的集合,像下面这样:

static void Main(string[] args){var files = from fileName in Directory.EnumerateFiles("c://", "test")let file = new FileInfo(fileName)orderby file.LastAccessTime, fileName descendingselect file into tempwhere temp.FullName != "123"select temp;}

前面文章中，使用selectMany,如果用linq 语句如何写呢?

static void Main(string[] args){List list = new List();BasketballTeam basketballTeam = new BasketballTeam();basketballTeam.Name = "无敌球队";basketballTeam.TeamMember = new string[] { "张三", "李四", "王五" };BasketballTeam basketballTeam1 = new BasketballTeam();basketballTeam1.Name = "小新球团";basketballTeam1.TeamMember = new string[] { "张嘛子", "李老帽", "王七三" };list.Add(basketballTeam);list.Add(basketballTeam1);var test = from team in list   from member in team.TeamMember   select team.Name + " "+ member;Console.ReadKey();}

使用两个from处理子集的情况。

结

linq 基础篇完成，后续为集合篇或者异步篇。