LinqToObject（2）——自由自在

做者: 梅桦 发表于 2010-05-07 10:28 原文连接 阅读: 67 评论: 0

对于Linq查询有几个要点，数据源，元素，投影。把握这几个要点，那么运用起来驾轻就熟。 

（一）查找句子

这里指的句是是英文句子，英文句子以.!?结束（逗点，叹号，问号）。下面摘取《The Call of the Wild》一段来进行介绍。

先来一大段：

string str=@"There he lay for the remainder of the weary night, nursing his wrath"+

@"and wounded pride. He could not understand what it all meant. What"+

@"did they want with him, these strange men? Why were they keeping"+

@"him pent up in this narrow crate? He did not know why, but he felt"+

@"oppressed by the vague sense of impending calamity. Several times"+

@"during the night he sprang to his feet when the shed door rattled open,"+

@"expecting to see the Judge, or the boys at least. But each time it was"+

@"the bulging face of the saloon-keeper that peered in at him by the sickly"+

@"light of a tallow candle. And each time the joyful bark that trembled in"+

@"Buck's throat was twisted into a savage growl.";

 

而后，查找带有“Buck”的句子，并分别打印出来。

首先，这里的数据源就是这个字符串（或者说这个段落），而后元素就是想要的每一个句子，投影也是句子，就是要段落中的全部句子。

获取数据源：数据源应该是句子集合，对于字符串来讲，直接的进行Linq查询，那么它的元素将是一个一个的字符，因此这里要获得数据源：

string [] sentences = str.Split( new   char []{ ' . ' , ' ? ' , ' ! ' });

 

用来分隔句子。如今的结果是：

There he lay for the remainder of the weary night, nursing his wrathand wounded pride

He could not understand what it all meant

Whatdid they want with him, these strange men

Why were they keepinghim pent up in this narrow crate

He did not know why, but he feltoppressed by the vague sense of impending calamity

Several timesduring the night he sprang to his feet when the shed door rattled open, expecting to see the Judge, or the boys at least

But each time it wasthe bulging face of the saloon-keeper that peered in at him by the sicklylight of a tallow candle

And each time the joyful bark that trembled inBuck's throat was twisted into a savage growl

 

而后，对于含有“Buck”的句子就是其中的元素，它的类型是字符串；而所须要就是这些句子。

var q1 = from p  in  sentences
         where  p.Contains( " Buck " )
        select p;

  

And each time the joyful bark that trembled inBuck's throat was twisted into a savage growl

  

上边查出的句子前边有空格，如今去除空格，这里用正则表达式来完成。

这个相对比较简单：

var q1 = from p  in  sentences
         where  p.Contains( " Buck " )
        select Regex.Replace(p, @" ^\  " , "" );

  

And each time the joyful bark that trembled inBuck's throat was twisted into a savage growl

（二）遍历文件

遍历目录下的全部文件并打印：

DirectoryInfo path  =   new  DirectoryInfo( @" L:\css " );
FileInfo[] fileinfos  =  path.GetFiles(); 

var q  =  from p  in  fileinfos
         elect  new  { 文件名  =  p.Name, 文件大小  =  p.Length  /   1024  };
q.Dump();

 

我如今打印的是目录下的文件：

 

文件名	文件大小
1.jpg	247
float.htm	0
……	……
连接.htm	0

 

上边只是遍历了目录下的文件，而对于其中的文件夹中的文件没能查询到，下边实现遍历全路径，方法很简单：

DirectoryInfo path  =   new  DirectoryInfo( @" L:\css " );
FileInfo[] fileinfos  =  path.GetFiles( " * " , SearchOption.AllDirectories); 

var q  =  from p  in  fileinfos
         select  new  
       { 文件名  =  p.Name, 文件大小  =  p.Length  /   1024 , 文件路径  =  p.FullName };

q.Dump();

   

文件名	文件大小	文件路径
1.jpg	247	L:\css\1.jpg
float.htm	0	L:\css\float.htm
……	……	……
qq.gif	25	L:\css\pic\qq.gif
t.png	15	L:\css\pic\t.png

 

找到数据源，明确其中的元素单位，并按所需进行投影设置。

 

（三）查找最大的文件

按文件大小排序，并经过元素选择来获得文件

DirectoryInfo path  =   new  DirectoryInfo( @" L:\css " );
FileInfo[] fileinfos  =  path.GetFiles( " * " , SearchOption.AllDirectories);

var q  =  (from p  in  fileinfos
          orderby p.Length
          select p).Last();
Console.Write(q.FullName);

 

（四）在文本文件中查找字符串

查找带有指定字符串的文件

var q  =  from p  in  fileinfos
          where  p.Extension  ==   " .htm "
         select p.FullName;

  

先指定筛选条件文件文件，扩展名为htm的文件，而后投影选择文件全名。而后在投影以前添加对文本文件中的字符串的查找：

DirectoryInfo path  =   new  DirectoryInfo( @" L:\css " );
FileInfo[] files  =  path.GetFiles( " * " , SearchOption.AllDirectories); 

var q  =  from p  in  files
         where  p.Extension  ==   " .htm "
         &&  GetFileContent(p.FullName).Contains( " 导航 " )
        select p;

foreach  (var info  in  q)
    Console.WriteLine(info.FullName);

  

GetFileContent方法是经过路径读取文本文件内容。

结果略。

这里提一下let关键字。Let相似mssql中的declare，用于声明局部变量

var q  =  from p  in  files
          where  p.Extension  ==   " .htm "
         let strContent =  GetFileContent(p.FullName)
          where  strContent.Contains( " 导航 " )
         select p;

  

这里设置strContent变量，而后再经过另外一个where来与上过滤条件。Let很是有用。

 

评论: 0 查看评论 发表评论

程序员找工做，就在博客园

最新新闻：
· 电子商务网站之信任度(2010-10-09 17:02)
· 马云：管理的核心在于“抓住人性的本真”(2010-10-09 16:52)
· 另外一 Windows Phone Live 主页截图现身 Windows Phone 7 视频(2010-10-09 16:38)
· 谷歌首名员工：公司成功归结于运气不错(2010-10-09 16:32)
· 神奇小子Geohot带着“limera1n”回归(2010-10-09 16:29)

编辑推荐：远离.NET

网站导航：博客园首页  我的主页  新闻  闪存  小组  博问  社区  知识库