[c#] Log4net rolling daily filename with date in the file name

I would like to have files named for example:

dd.mm.yyyy.log

How is this possible with log4net?

I've tried all the answers, but there was always something missing and not functioning as expected for me.

Then I experimented a bit with the hints given in each answer and was successful with the following setting:

<appender name="RollingActivityLog" type="log4net.Appender.RollingFileAppender">
  <file type="log4net.Util.PatternString" value="C:\temp\LOG4NET_Sample_Activity.log" />
  <appendToFile value="true" />
  <rollingStyle value="Date" />
  <staticLogFileName value="false" />
  <preserveLogFileNameExtension value="true" />
  <datePattern value="-yyyyMMdd" />
  <layout type="log4net.Layout.PatternLayout">
    <conversionPattern value="%date %-5level - %message%newline" />
  </layout>
</appender>

The issue with other combinations of parameters was that the latest file didn't have the time pattern, or that the time pattern was appended as .log20171215 which created a new file time (and a new file type!) each day - or both issues appeared.

Now with this setting you are getting files like this one:

LOG4NET_Sample_Activity-20171215.log

which is what I wanted.

To summarize:

• Don't put the date pattern in the <file value=... attribute, just define it in the datePattern.

• Make sure you have the preserveLogFileNameExtension value attribute set to true.

• Make sure you have the staticLogFileName value set to false.

• Set the rollingStyle attribute value to Date.

For a RollingLogFileAppender you also need these elements and values:

<rollingStyle value="Date" />
<staticLogFileName value="false" />

To preserve file extension:

<log4net>
    <root>
      <level value="DEBUG"/>
      <appender-ref ref="RollingLogFileAppender"/>
    </root>
    <appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
      <file type="log4net.Util.PatternString" value="D:\\LogFolder\\%date{yyyyMM}\\SchT.log" />
      <appendToFile value="true" />
      <rollingStyle value="Date" />
      <maximumFileSize value="30MB" />
      <staticLogFileName value="true" />
      <preserveLogFileNameExtension value="true"/>
      <datePattern value="ddMMyyyy" />
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%date [%thread] %-5level %logger - %message%newline" />
      </layout>
    </appender>
  </log4net>

The extended configuration section in a previous response with

 ...
 ...
 <rollingStyle value="Composite" />
 ...
 ...

listed works but I did not have to use

<staticLogFileName value="false" /> 

. I think the RollingAppender must (logically) ignore that setting since by definition the file gets rebuilt each day when the application restarts/reused. Perhaps it does matter for immediate rollover EVERY time the application starts.

Using Log4Net 1.2.13 we use the following configuration settings to allow date time in the file name.

<file type="log4net.Util.PatternString" value="E:/logname-%utcdate{yyyy-MM-dd}.txt" />

Which will provide files in the following convention: logname-2015-04-17.txt

With this it's usually best to have the following to ensure you're holding 1 log per day.

<rollingStyle value="Date" />
<datePattern value="yyyyMMdd" />

If size of file is a concern the following allows 500 files of 5MB in size until a new day spawns. CountDirection allows Ascending or Descending numbering of files which are no longer current.

 <maxSizeRollBackups value="500" />
 <maximumFileSize value="5MB" />
 <rollingStyle value="Composite" />
 <datePattern value="yyyyMMdd" />
 <CountDirection value="1"/>
 <staticLogFileName value="true" />

I moved configuration to code to enable easy modification from CI using system variable. I used this code for file name and result is 'Log_03-23-2020.log'

            log4net.Repository.ILoggerRepository repository = LogManager.GetRepository(Assembly.GetEntryAssembly());
            Hierarchy hierarchy = (Hierarchy)repository;
            PatternLayout patternLayout = new PatternLayout();
            patternLayout.ConversionPattern = "%date %level - %message%newline%exception";
            patternLayout.ActivateOptions();

            RollingFileAppender roller = new RollingFileAppender();
            roller.AppendToFile = true;
            roller.File = "Log_";
            roller.DatePattern = "MM-dd-yyyy'.log'";
            roller.Layout = patternLayout;
            roller.MaxFileSize = 1024*1024*10;
            roller.MaxSizeRollBackups = 10;
            roller.StaticLogFileName = false;
            roller.RollingStyle = RollingFileAppender.RollingMode.Composite;
            roller.ActivateOptions();
            hierarchy.Root.AddAppender(roller);

I ended up using (note the '.log' filename and the single quotes around 'myfilename_'):

  <rollingStyle value="Date" />
  <datePattern value="'myfilename_'yyyy-MM-dd"/>
  <preserveLogFileNameExtension value="true" />
  <staticLogFileName value="false" />
  <file type="log4net.Util.PatternString" value="c:\\Logs\\.log" />

This gives me:

myfilename_2015-09-22.log
myfilename_2015-09-23.log
.
.

<appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
  <lockingModel type="log4net.Appender.FileAppender+MinimalLock"/>
  <file value="logs\" />
  <datePattern value="dd.MM.yyyy'.log'" />
  <staticLogFileName value="false" />
  <appendToFile value="true" />
  <rollingStyle value="Composite" />
  <maxSizeRollBackups value="10" />
  <maximumFileSize value="5MB" />
  <layout type="log4net.Layout.PatternLayout">
    <conversionPattern value="%date [%thread] %-5level %logger [%property{NDC}] - %message%newline" />
  </layout>
</appender>