检查文件是否存在 [英] Check if File exists

问题描述

大家好。


我有这个问题，我看看文件是否存在，如果不等待

直到它被创建，如果它存在，我需要打开它。我执行以下操作：

for（;;）


{


if（fl.Exists）


{


StreamReader sr = fl.OpenText（）;


StreamWriter sw = new StreamWriter （FILE_NAME）;


字符串行;


while（（line = sr.ReadLine（））！= null）


{


if（！line.Contains（" Pagina））


sw.WriteLine（线路）;


}


sr.Close（）;


sw.Close（ ）;


}


}


问题在于它在检查时如果文件存在，则cpu加载为
100％。


有没有办法每秒检查一次？比如等待1秒他们

再次检查？


或任何其他方法???


Thx ..

Hi all.

I''m having a problem with this, I have look if a file exists, if don''t wait
till it is created and if it exists I need to open it. I do the following:
for (; ; )

{

if (fl.Exists)

{

StreamReader sr = fl.OpenText();

StreamWriter sw = new StreamWriter(FILE_NAME);

String line;

while ((line = sr.ReadLine()) != null)

{

if (!line.Contains("Pagina"))

sw.WriteLine(line);

}

sr.Close();

sw.Close();

}

}

The problem is that when it''s checking if the file exists the cpu load is in
100%.

Is there a way to do that check once per second?? like an wait 1 second them
check it again??

Or any other method???

Thx..

推荐答案

里卡多，


你可以放要休眠的线程，或者有一个计时器每隔一段时间触发一次，但这是一个很昂贵的操作。


查看FileSystemWatcher类。您可以监视目录以进行

更改，当有更改时，将通知您的代码。它比循环和检查文件的存在要少得多。相反，你会在有变化时通知
，如果是你要查找的文件，那么你可以处理它。


希望这会有所帮助。

-

- Nicholas Paldino [.NET / C＃MVP]

- < a href =mailto：mv*@spam.guard.caspershouse.com> mv*@spam.guard.caspershouse.com


" Ricardo Luceac" < RL ***** @ gmail.com>在消息中写道

新闻：eK ************** @ TK2MSFTNGP11.phx.gbl ...

Ricardo,

You could just put the thread to sleep, or have a timer that fires every
minute, but this is an expensive operation.

Check out the FileSystemWatcher class. You can monitor a directory for
changes, and when there are changes, your code will be notified. It is less
intensive than looping and checking the existence of a file. Instead, you
will just be notified when there is a change, and if it is the file you are
looking for, then you can process it.

Hope this helps.
--
- Nicholas Paldino [.NET/C# MVP]
- mv*@spam.guard.caspershouse.com

"Ricardo Luceac" <rl*****@gmail.com> wrote in message
news:eK**************@TK2MSFTNGP11.phx.gbl...

大家好。

我遇到了这个问题，我看看文件是否存在，如果不等待它创建，如果它存在，我需要打开它。我做了
以下：

for（;;）

{

if（fl.Exists）
< StreamReader sr = fl.OpenText（）;

StreamWriter sw = new StreamWriter（FILE_NAME）;

字符串行; <同时（（line = sr.ReadLine（））！= null）

如果（！line.Contains（" Pagina） ））

sw.WriteLine（line）;

}
sr.Close（）;

sw。关闭（）;

}


问题是，当它检查文件是否存在时，cpu加载是

有没有办法每秒检查一次？喜欢等待1秒
他们再检查一下？

或任何其他方法???

Thx ..

Hi all.

I''m having a problem with this, I have look if a file exists, if don''t
wait till it is created and if it exists I need to open it. I do the
following:
for (; ; )

{

if (fl.Exists)

{

StreamReader sr = fl.OpenText();

StreamWriter sw = new StreamWriter(FILE_NAME);

String line;

while ((line = sr.ReadLine()) != null)

{

if (!line.Contains("Pagina"))

sw.WriteLine(line);

}

sr.Close();

sw.Close();

}

}

The problem is that when it''s checking if the file exists the cpu load is
in 100%.

Is there a way to do that check once per second?? like an wait 1 second
them check it again??

Or any other method???

Thx..

你好，


我看到的问题是循环不断循环而没有

停止，这就是cpu为100％的原因。

在for循环结束前插入：


Thread.sleep代码（1000）; // 1000 = 1秒


使用此方法线程将等待一秒钟，然后再次检查

文件


-

问候，

DavidHernándezDíez

MCDBA MCSD vs6& .NET

DCE5 .Net1.1& DCE2 .NET 2.0

Ricardo Luceac写道：

Hello,

The problem I see is that the loop is continuously looping without
stopping, that''s why the cpu is at 100%.

Insert just before the end of the for loop:

Thread.Sleep(1000); //1000 = 1 second

With this method the thread will wait one second, before checking the
file again

--
Regards,
David Hernández Díez
MCDBA MCSD vs6 & .NET
DCE5 .Net1.1 & DCE2 .NET 2.0

Ricardo Luceac wrote:

大家好。

我有这个问题，我看看文件是否存在，如果不等待，直到它被创建，如果存在，我需要打开它。我执行以下操作：

for（;;）

{

if（fl.Exists）

{

StreamReader sr = fl.OpenText（）;

StreamWriter sw = new StreamWriter（FILE_NAME）;

字符串行;

while（（line = sr.ReadLine（））！= null）

如果（！line.Contains（" Pagina"））

sw.WriteLine（line）;


sr.Close（）;

sw.Close（）;

}


问题是当它检查文件是否存在时，cpu加载是否在100中％。

有没有办法每秒检查一次？比如等待1秒他们再次检查一下？

或者其他任何方法???

Thx ..

Hi all.

I''m having a problem with this, I have look if a file exists, if don''t wait
till it is created and if it exists I need to open it. I do the following:
for (; ; )

{

if (fl.Exists)

{

StreamReader sr = fl.OpenText();

StreamWriter sw = new StreamWriter(FILE_NAME);

String line;

while ((line = sr.ReadLine()) != null)

{

if (!line.Contains("Pagina"))

sw.WriteLine(line);

}

sr.Close();

sw.Close();

}

}

The problem is that when it''s checking if the file exists the cpu load is in
100%.

Is there a way to do that check once per second?? like an wait 1 second them
check it again??

Or any other method???

Thx..

没有c＃的说法...


而fileexists = false ....

{

//什么都不做......

}


？

Ricardo Luceac < RL ***** @ gmail.com>在消息中写道

新闻：eK ************** @ TK2MSFTNGP11.phx.gbl ...

Is there no c# way of saying...

while fileexists=false....
{
// Do nothing...
}

?
"Ricardo Luceac" <rl*****@gmail.com> wrote in message
news:eK**************@TK2MSFTNGP11.phx.gbl...

大家好。

我遇到了这个问题，我看看文件是否存在，如果不等待它创建，如果它存在，我需要打开它。我做了
以下：

for（;;）

{

if（fl.Exists）
< StreamReader sr = fl.OpenText（）;

StreamWriter sw = new StreamWriter（FILE_NAME）;

字符串行; <同时（（line = sr.ReadLine（））！= null）

如果（！line.Contains（" Pagina） ））

sw.WriteLine（line）;

}
sr.Close（）;

sw。关闭（）;

}


问题是，当它检查文件是否存在时，cpu加载是

有没有办法每秒检查一次？喜欢等待1秒
他们再检查一下？

或任何其他方法???

Thx ..

Hi all.

I''m having a problem with this, I have look if a file exists, if don''t
wait till it is created and if it exists I need to open it. I do the
following:
for (; ; )

{

if (fl.Exists)

{

StreamReader sr = fl.OpenText();

StreamWriter sw = new StreamWriter(FILE_NAME);

String line;

while ((line = sr.ReadLine()) != null)

{

if (!line.Contains("Pagina"))

sw.WriteLine(line);

}

sr.Close();

sw.Close();

}

}

The problem is that when it''s checking if the file exists the cpu load is
in 100%.

Is there a way to do that check once per second?? like an wait 1 second
them check it again??

Or any other method???

Thx..

这篇关于检查文件是否存在的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！