How to activate logging in runtime without restarting application?

It is possible to activate logging in Serilog or NLog without restart .NET application?

I want to activate logging while the application is running on the customers system to see what's wrong.

Solution

One of the main features of NLog is that you could change the config while running the application.

If you have a nlog.config, you could enable autoreload:

<nlog autoReload="true">
   ...
</nlog>

Then the config will be reloaded when you save the changes to the file.

Example

For example:

In the config you could change the globalThreshold or the <rules> while running.

<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      autoReload="true"
      globalThreshold="Debug" >

  <!-- the targets to write to -->
  <targets>
    <!-- write logs to file  -->
    <target xsi:type="File" name="file1" fileName="c:\temp\nlog-all-${shortdate}.log"
            layout="${longdate}|${event-properties:item=EventId_Id}|${uppercase:${level}}|${logger}|${message} ${exception:format=tostring}" />

  </targets>

  <!-- rules to map from logger name to target -->
  <rules>
    <logger name="*" minlevel="Trace" writeTo="file1" />
  </rules>

</nlog>

From code

You could also change the config from code, then check LogManager.Configuration. Please note that this property is null if you haven't a config yet (from code or nlog.config).