blocks|key|3094233|text|使用File.AppendAllText代替：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3094234|File.AppendAllText(filePath+%2B+"log.txt",+log);|code-block|syntax|javascript|3094235|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/ms143356%2528v=vs.110%2529.aspx^0|2|I|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Use <a href="http://msdn.microsoft.com/en-us/library/ms143356%28v=vs.110%29.aspx">File.AppendAllText</a> instead:

<pre><code>File.AppendAllText(filePath + "log.txt", log);
</code></pre>

blocks|key|584361|text|if(!File.Exists(filename))+//No+File?+Create
{
++++fs+=+File.Create(filename);
++++fs.Close();
}
if(File.ReadAllBytes().Length+>=+100*1024*1024)+//+(100mB)+File+to+big?+Create+new
{
++++string+filenamebase+=+"myLogFile";+//Insert+the+base+form+of+the+log+file,+the+same+as+the+1st+filename+without+.log+at+the+end
++++if(filename.contains("-"))+//Check+if+older+log+contained+-x
++++{
+++++++++int+lognumber+=+Int32.Parse(filename.substring(filename.lastIndexOf("-")%2B1,+filename.Length-4);+//Get+old+number,+Can+cause+exception+if+the+last+digits+aren't+numbers
+++++++++lognumber%2B%2B;+//Increment+lognumber+by+1
+++++++++filename+=+filenamebase+%2B+"-"+%2B+lognumber+%2B+".log";+//Override+filename
++++}
++++else+
++++{
+++++++++filename+=+filenamebase+%2B+"-1.log";+//Override+filename
++++}
++++fs+=+File.Create(filename);
++++fs.Close();
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|584362|参考链接：|unstyled|584363|http://www.codeproject.com/Questions/163337/How-to-write-in-log-Files-in-C|offset|length|584364|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|22|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|S|8|@]|9|@]|A|$]]|$1|G|3|H|5|F|7|T|8|@]|9|@$I|U|J|V|1|W]]|A|$]]|$1|K|3|-4|5|F|7|X|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|H]]]]

<pre><code>if(!File.Exists(filename)) //No File? Create
{
 fs = File.Create(filename);
 fs.Close();
}
if(File.ReadAllBytes().Length &gt;= 100*1024*1024) // (100mB) File to big? Create new
{
 string filenamebase = "myLogFile"; //Insert the base form of the log file, the same as the 1st filename without .log at the end
 if(filename.contains("-")) //Check if older log contained -x
 {
 int lognumber = Int32.Parse(filename.substring(filename.lastIndexOf("-")+1, filename.Length-4); //Get old number, Can cause exception if the last digits aren't numbers
 lognumber++; //Increment lognumber by 1
 filename = filenamebase + "-" + lognumber + ".log"; //Override filename
 }
 else 
 {
 filename = filenamebase + "-1.log"; //Override filename
 }
 fs = File.Create(filename);
 fs.Close();
}
</code></pre>

Refer link:

<a href="http://www.codeproject.com/Questions/163337/How-to-write-in-log-Files-in-C" rel="nofollow">http://www.codeproject.com/Questions/163337/How-to-write-in-log-Files-in-C</a>

blocks|key|3094256|text|非常方便的日志记录工具是http://logging.apache.org/log4net/。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3094257|你也可以让自己的东西变得更小(更强大)。您可以使用http://msdn.microsoft.com/ru-ru/library/system.io.filestream+(v+=+vs.110).+Aspx|3094258|entityMap|0|LINK|mutability|MUTABLE|url|http://logging.apache.org/log4net/|1|http://msdn.microsoft.com/ru-ru/library/system.io.filestream%2520%2528v%2520=%2520vs.110%2529.%2520Aspx^0|C|Y|0|0|P|27|1|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@$A|U|B|V|1|W]]|C|$]]|$1|F|3|-4|5|6|7|X|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]|N|$5|I|J|K|C|$L|O]]]]

Very convenient tool for logging is <a href="http://logging.apache.org/log4net/">http://logging.apache.org/log4net/</a> 

You can also make something of themselves less (more) powerful. You can use <a href="http://msdn.microsoft.com/ru-ru/library/system.io.filestream%20%28v%20=%20vs.110%29.%20Aspx">http://msdn.microsoft.com/ru-ru/library/system.io.filestream (v = vs.110). Aspx</a>

blocks|key|2013496|text|创建一个类，全局创建一个对象，并调用它|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2013497|using+System.IO;
using+System.Reflection;


+++public+class+LogWriter
{
++++private+string+m_exePath+=+string.Empty;
++++public+LogWriter(string+logMessage)
++++{
++++++++LogWrite(logMessage);
++++}
++++public+void+LogWrite(string+logMessage)
++++{
++++++++m_exePath+=+Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
++++++++try
++++++++{
++++++++++++using+(StreamWriter+w+=+File.AppendText(m_exePath+%2B+"\\"+%2B+"log.txt"))
++++++++++++{
++++++++++++++++Log(logMessage,+w);
++++++++++++}
++++++++}
++++++++catch+(Exception+ex)
++++++++{
++++++++}
++++}

++++public+void+Log(string+logMessage,+TextWriter+txtWriter)
++++{
++++++++try
++++++++{
++++++++++++txtWriter.Write("\r\nLog+Entry+:+");
++++++++++++txtWriter.WriteLine("{0}+{1}",+DateTime.Now.ToLongTimeString(),
++++++++++++++++DateTime.Now.ToLongDateString());
++++++++++++txtWriter.WriteLine("++:");
++++++++++++txtWriter.WriteLine("++:{0}",+logMessage);
++++++++++++txtWriter.WriteLine("-------------------------------");
++++++++}
++++++++catch+(Exception+ex)
++++++++{
++++++++}
++++}
}|code-block|syntax|javascript|2013498|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

create a class create a object globally and call this

<pre><code>using System.IO;
using System.Reflection;


 public class LogWriter
{
 private string m_exePath = string.Empty;
 public LogWriter(string logMessage)
 {
 LogWrite(logMessage);
 }
 public void LogWrite(string logMessage)
 {
 m_exePath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
 try
 {
 using (StreamWriter w = File.AppendText(m_exePath + "\\" + "log.txt"))
 {
 Log(logMessage, w);
 }
 }
 catch (Exception ex)
 {
 }
 }

 public void Log(string logMessage, TextWriter txtWriter)
 {
 try
 {
 txtWriter.Write("\r\nLog Entry : ");
 txtWriter.WriteLine("{0} {1}", DateTime.Now.ToLongTimeString(),
 DateTime.Now.ToLongDateString());
 txtWriter.WriteLine(" :");
 txtWriter.WriteLine(" :{0}", logMessage);
 txtWriter.WriteLine("-------------------------------");
 }
 catch (Exception ex)
 {
 }
 }
}
</code></pre>

blocks|key|3094326|text|这是在文件中添加新字符串。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3094327|using+(var+file+=+new+StreamWriter(filePath+%2B+"log.txt",+true))
++++++++{
++++++++++++file.WriteLine(log);
++++++++++++file.Close();
++++++++}|code-block|syntax|javascript|3094328|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This is add new string in the file

<pre><code>using (var file = new StreamWriter(filePath + "log.txt", true))
 {
 file.WriteLine(log);
 file.Close();
 }
</code></pre>

blocks|key|586439|text|从性能的角度来看，您的解决方案不是最优的。每次使用%2B=添加另一个日志条目时，都会将整个字符串复制到内存中的另一个位置。我建议使用StringBuilder来代替：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|586440|StringBuilder+sb+=+new+StringBuilder();
...
sb.Append("log+something");

...
//+flush+every+20+seconds+as+you+do+it
File.AppendAllText(filePath%2B"log.txt",+sb.ToString());
sb.Clear();|code-block|syntax|javascript|586441|顺便说一下，计时器事件可能是在另一个线程上执行的。因此，您可能需要在访问sb对象时使用互斥对象。|offset|length|style|CODE|586442|另一件需要考虑的事情是，在执行之后的20秒内添加的日志条目发生了什么。您可能希望在应用程序退出之前将您的字符串刷新到文件中。|586443|entityMap^0|0|0|10|2|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|V|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

From the performance point of view your solution is not optimal. Every time you add another log entry with +=, the whole string is copied to another place in memory. I would recommend using StringBuilder instead:

<pre><code>StringBuilder sb = new StringBuilder();
...
sb.Append("log something");

...
// flush every 20 seconds as you do it
File.AppendAllText(filePath+"log.txt", sb.ToString());
sb.Clear();
</code></pre>

By the way your timer event is probably executed on another thread. So you may want to use a mutex when accessing your <code>sb</code> object.

Another thing to consider is what happens to the log entries that were added within the last 20 seconds of the execution. You probably want to flush your string to the file right before the app exits.

blocks|key|2013586|text|有两个简单的方法|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2013587|StreamWriter+-+http://www.dotnetperls.com/streamwriter|unordered-list-item|offset|length|2013588|Log4Net类Log4j(Java)+-+http://www.codeproject.com/Articles/140911/log4net-Tutorial|2013589|entityMap|0|LINK|mutability|MUTABLE|url|http://www.dotnetperls.com/streamwriter|1|http://www.codeproject.com/Articles/140911/log4net-Tutorial^0|0|F|13|0|0|M|1N|1|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@$E|U|F|V|1|W]]|A|$]]|$1|G|3|H|5|D|7|X|8|@]|9|@$E|Y|F|Z|1|10]]|A|$]]|$1|I|3|-4|5|6|7|11|8|@]|9|@]|A|$]]]|J|$K|$5|L|M|N|A|$O|P]]|Q|$5|L|M|N|A|$O|R]]]]

There are 2 easy ways 

<ul>
<li>StreamWriter - <a href="http://www.dotnetperls.com/streamwriter" rel="nofollow">http://www.dotnetperls.com/streamwriter</a></li>
<li>Log4Net like Log4j(Java) - <a href="http://www.codeproject.com/Articles/140911/log4net-Tutorial" rel="nofollow">http://www.codeproject.com/Articles/140911/log4net-Tutorial</a></li>
</ul>

blocks|key|584404|text|public+static+void+WriteLog(string+strLog)
++++{
++++++++StreamWriter+log;
++++++++FileStream+fileStream+=+null;
++++++++DirectoryInfo+logDirInfo+=+null;
++++++++FileInfo+logFileInfo;

++++++++string+logFilePath+=+"C:\\Logs\\";
++++++++logFilePath+=+logFilePath+%2B+"Log-"+%2B+System.DateTime.Today.ToString("MM-dd-yyyy")+%2B+"."+%2B+"txt";+++++++++++
++++++++logFileInfo+=+new+FileInfo(logFilePath);
++++++++logDirInfo+=+new+DirectoryInfo(logFileInfo.DirectoryName);
++++++++if+(!logDirInfo.Exists)+logDirInfo.Create();
++++++++if+(!logFileInfo.Exists)
++++++++{
++++++++++++fileStream+=+logFileInfo.Create();
++++++++}
++++++++else
++++++++{
++++++++++++fileStream+=+new+FileStream(logFilePath,+FileMode.Append);
++++++++}
++++++++log+=+new+StreamWriter(fileStream);
++++++++log.WriteLine(strLog);
++++++++log.Close();
++++}+++|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|584405|参考链接：blogspot.in|unstyled|offset|length|584406|entityMap|0|LINK|mutability|MUTABLE|url|http://linktomohankumar.blogspot.in/2014/09/create-log-file-using-cnet.html^0|0|5|B|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|R|8|@]|9|@$G|S|H|T|1|U]]|A|$]]|$1|I|3|-4|5|F|7|V|8|@]|9|@]|A|$]]]|J|$K|$5|L|M|N|A|$O|P]]]]

<pre><code>public static void WriteLog(string strLog)
 {
 StreamWriter log;
 FileStream fileStream = null;
 DirectoryInfo logDirInfo = null;
 FileInfo logFileInfo;

 string logFilePath = "C:\\Logs\\";
 logFilePath = logFilePath + "Log-" + System.DateTime.Today.ToString("MM-dd-yyyy") + "." + "txt"; 
 logFileInfo = new FileInfo(logFilePath);
 logDirInfo = new DirectoryInfo(logFileInfo.DirectoryName);
 if (!logDirInfo.Exists) logDirInfo.Create();
 if (!logFileInfo.Exists)
 {
 fileStream = logFileInfo.Create();
 }
 else
 {
 fileStream = new FileStream(logFilePath, FileMode.Append);
 }
 log = new StreamWriter(fileStream);
 log.WriteLine(strLog);
 log.Close();
 } 
</code></pre>

Refer Link:
<a href="http://linktomohankumar.blogspot.in/2014/09/create-log-file-using-cnet.html" rel="noreferrer">blogspot.in</a>

blocks|key|586462|text|使用静态类将日志添加到文件|type|unstyled|depth|inlineStyleRanges|entityRanges|data|586463|+public+static+class+LogWriter
++++++++{
++++++++++++private+static+string+m_exePath+=+string.Empty;
++++++++++++public+static+void+LogWrite(string+logMessage)
++++++++++++{
++++++++++++++++m_exePath+=+Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
++++++++++++++++if+(!File.Exists(m_exePath+%2B+"\\"+%2B+"log.txt"))
++++++++++++++++++++File.Create(m_exePath+%2B+"\\"+%2B+"log.txt");

++++++++++++++++try
++++++++++++++++{
++++++++++++++++++++using+(StreamWriter+w+=+File.AppendText(m_exePath+%2B+"\\"+%2B+"log.txt"))
++++++++++++++++++++++++AppendLog(logMessage,+w);
++++++++++++++++}
++++++++++++++++catch+(Exception+ex)
++++++++++++++++{
++++++++++++++++++++Console.WriteLine(ex.Message);
++++++++++++++++}

++++++++++++}

++++++++++++private+static+void+AppendLog(string+logMessage,+TextWriter+txtWriter)
++++++++++++{
++++++++++++++++try
++++++++++++++++{
++++++++++++++++++++txtWriter.Write("\r\nLog+Entry+:+");
++++++++++++++++++++txtWriter.WriteLine("{0}+{1}",+DateTime.Now.ToLongTimeString(),DateTime.Now.ToLongDateString());
++++++++++++++++++++txtWriter.WriteLine("++:");
++++++++++++++++++++txtWriter.WriteLine("++:{0}",+logMessage);
++++++++++++++++++++txtWriter.WriteLine("-------------------------------");
++++++++++++++++}
++++++++++++++++catch+(Exception+ex)
++++++++++++++++{
++++++++++++++++}
++++++++++++}
++++++++}|code-block|syntax|javascript|586464|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Add log to file with Static Class 

<pre><code> public static class LogWriter
 {
 private static string m_exePath = string.Empty;
 public static void LogWrite(string logMessage)
 {
 m_exePath = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
 if (!File.Exists(m_exePath + "\\" + "log.txt"))
 File.Create(m_exePath + "\\" + "log.txt");

 try
 {
 using (StreamWriter w = File.AppendText(m_exePath + "\\" + "log.txt"))
 AppendLog(logMessage, w);
 }
 catch (Exception ex)
 {
 Console.WriteLine(ex.Message);
 }

 }

 private static void AppendLog(string logMessage, TextWriter txtWriter)
 {
 try
 {
 txtWriter.Write("\r\nLog Entry : ");
 txtWriter.WriteLine("{0} {1}", DateTime.Now.ToLongTimeString(),DateTime.Now.ToLongDateString());
 txtWriter.WriteLine(" :");
 txtWriter.WriteLine(" :{0}", logMessage);
 txtWriter.WriteLine("-------------------------------");
 }
 catch (Exception ex)
 {
 }
 }
 }
</code></pre>

blocks|key|586470|text|由@randymohan发布，用语句代替|type|unstyled|depth|inlineStyleRanges|entityRanges|data|586471|public+static+void+WriteLog(string+strLog)
{
++++string+logFilePath+=+@"C:\Logs\Log-"+%2B+System.DateTime.Today.ToString("MM-dd-yyyy")+%2B+"."+%2B+"txt";
++++FileInfo+logFileInfo+=+new+FileInfo(logFilePath);
++++DirectoryInfo+logDirInfo+=+new+DirectoryInfo(logFileInfo.DirectoryName);
++++if+(!logDirInfo.Exists)+logDirInfo.Create();
++++using+(FileStream+fileStream+=+new+FileStream(logFilePath,+FileMode.Append))
++++{
++++++++using+(StreamWriter+log+=+new+StreamWriter(fileStream))
++++++++{
++++++++++++log.WriteLine(strLog);
++++++++}
++++}
}|code-block|syntax|javascript|586472|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

as posted by @randymohan, with using statements instead

<pre><code>public static void WriteLog(string strLog)
{
 string logFilePath = @"C:\Logs\Log-" + System.DateTime.Today.ToString("MM-dd-yyyy") + "." + "txt";
 FileInfo logFileInfo = new FileInfo(logFilePath);
 DirectoryInfo logDirInfo = new DirectoryInfo(logFileInfo.DirectoryName);
 if (!logDirInfo.Exists) logDirInfo.Create();
 using (FileStream fileStream = new FileStream(logFilePath, FileMode.Append))
 {
 using (StreamWriter log = new StreamWriter(fileStream))
 {
 log.WriteLine(strLog);
 }
 }
}
</code></pre>

blocks|key|3094450|text|如果您的应用程序是多线程的，那么在某些环境中，file.appendalltext可能会出现错误，就像已经在使用的文件一样，如果您跳过了该错误，那么您可能会丢失重要的日志。为此，您可以在file.append中使用锁对象技术。在这种情况下，它将等待现有进程关闭并写入日志。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3094451|这还可以避免在源代码中添加其他库。|3094452|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

If your application is multithreaded then in some environments file.appendalltext could give error like file already in use and if you skip that then you could lose important logs .
For that you can use
Lock object technique with file.append.. in that case it will wait for existing process to close and the write your log
This can also save you from adding other libraries in your source

How would I write a log file in c#?

Currently i have a timer with this statement which ticks every 20 secs:

<pre><code>File.WriteAllText(filePath+"log.txt", log);
</code></pre>

For everything that i want logged i do this: 

<pre><code>log += "stringToBeLogged";
</code></pre>

As you can assume the string log just grows and grows as the program runs. (I don't even know if there is a maximum chars per string?)

I assume that there must be better ways of doing this. i just thought that it would be heavy to write the whole file again and again for every time something is added to the log.

How to write log file in c#?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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如何用c#编写日志文件？目前，我有一个计时器，这个语句每20秒滴答一次：File.WriteAllText(filePath+"log.txt", log);对于我想要记录的所有内容，我都会这样做：log += "stringToBeLogged";因为您可以假设字符串日志只是随着程序的运行而增长。(我甚至不知道每个字...

问如何用c#编写日志文件？
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问如何用c#编写日志文件？EN