Change basedir in NLog Targets in runtime programmatically

Question

I have Windows Forms app NET 4.5 (VS 2013) using NLog.

I have targets:

<target name="asyncFileLog" xsi:type="AsyncWrapper">
  <target name="logfileTrace" xsi:type="File" fileName="${basedir}/logs/${shortdate}Trace.log" layout="${longdate} ${message}" lineEnding="Default"/>
</target>

<target name="asyncFileError" xsi:type="AsyncWrapper">
  <target name="logfileError" xsi:type="File" fileName="${basedir}/logs/${shortdate}Error.log" layout="${longdate} ${message} ${exception:format=tostring}"  lineEnding="Default"/>
</target>

LogManager.Configuration.AllTargets.ToList(); returns 4 items, not 2 items.

I want change the path ${basedir}/logs in runtime, programmatically

I try this:

var rutaLogs = ConfigurationManager.AppSettings["RutaLog"];
if (!Directory.Exists(rutaLogs)) return;

var list = LogManager.Configuration.AllTargets.ToList();
foreach (var target in list)
{
    FileTarget fileTarget = null;
    var wrapperTarget = target as WrapperTargetBase;

    // Unwrap the target if necessary.
    if (wrapperTarget == null)
    {
        fileTarget = target as FileTarget;
    }
    else
    {
        fileTarget = wrapperTarget.WrappedTarget as FileTarget;
        continue;
    }

    var value = fileTarget.FileName.ToString();
    value = value.Replace("${basedir}/logs/", rutaLogs);
    fileTarget.FileName = value;
}

Not generates anything. I try using LogManager.ReconfigExistingLoggers(); too, but not working.

Any suggestions?

Julian · Accepted Answer · 2017-03-02T20:14:13.323

It's easier to use variables in this case. (${var:...})

For this example:

<variable name="basedir" value="${basedir}" />    <!-- default, optional -->

<targets>
   <target name="asyncFileLog" xsi:type="AsyncWrapper">
     <target name="logfileTrace" xsi:type="File" 
             fileName="${var:basedir}/logs/${shortdate}Trace.log" 
             layout="${longdate} ${message}" lineEnding="Default"/> 
   </target>
   ...

Changing the variable in C#

// create or edit
LogManager.Configuration.Variables["basedir"] = "d:/mybasedir";

No need for LogManager.ReconfigExistingLoggers(); or looping over all the targets!

See also the ${var} documentation

Update: in this case your are reading from .config files, this could be done with only NLog configuration (no C# needed!)

Install NLog.Extended and use ${appsetting:name=..}

e.g.

fileName="${var:basedir}/logs/${appsetting:name=RutaLog}Trace.log"

See also the ${appsetting} documentation

Works using `fileName="${var:basedir}/logs/${shortdate}Trace.log"` and works using `fileName="${appsetting:name=RutaLog}${shortdate}Trace.log"`. Using ***${appsetting:name=key}*** is more clearly. — Kiquenet, Mar 28 '17 at 10:46
Great! The variables are only gets updated if we write it like ${var:MyVar} not just ${MyVar} — Amin Mohamed, Nov 25 '20 at 20:45

score 0 · Answer 2 · answered Jul 28 '20 at 13:25

Modify Nlog.Config like below:

<variable name="basedir" value="${basedir}" />  
  <targets async="true">

     <target name="fileAsync" xsi:type="File"  keepFileOpen="true" encoding="iso-8859-2" concurrentWrites="false"
            layout="${date:format=yyyy-MM-dd, HH\:mm\:ss.fff} | [${threadid}] | ${level:uppercase=true}&#009;| ${message}."
            fileName="${var:basedir}/Log/log_${date:format=yyyy-MM-dd}.log"
            archiveFileName="${var:basedir}/Log/archive/${date:format=yyyy}/${date:format=MM}/${date:format=dd}/log_${date:format=yyyy-MM-dd_hh}.log"
            archiveEvery="Day" maxArchiveFiles="2048" enableFileDelete="true" archiveAboveSize="53248000" />
  </targets>

Code behind: string str = LogManager.Configuration.Variables["basedir"].Text; LogManager.Configuration.Variables["basedir"] = @"D:\LogDir";

Change basedir in NLog Targets in runtime programmatically

2 Answers2