How to configure NLog to log only Errors in the Windows syslog?

Question

I'm trying to log only Errors into the Windows syslog (events viewer), I tried many solutions but none of them run as expected. I still see warning messages in the Windows syslog.

It's an Asp.Net Core project (nuget 2.2.0) with NLog 5.2.8, NLog.Web.AspNetCore, Version=4.0.0.0. I don't have any a content related to log configuration in my appsettings.json file and here is the content of my nglog.config file.

What am I missing?

<?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">
   <extensions>
      <add assembly="NLog.Web.AspNetCore"/>
      <add assembly="NLog.WindowsEventLog"/>
   </extensions>

   <targets>
      <target xsi:type="File" name="allfile" fileName="Backoffice_template.log" layout="${longdate}|${event-properties:item=EventId_Id}|${uppercase:${level}}|${logger}|${message} ${exception:format=tostring} |action: ${aspnet-mvc-action} |user: ${aspnet-user-identity}" archiveEvery="Day" encoding="utf-8"
                   archiveNumbering = "Date"
                   archiveDateFormat = "yyyyMMdd_HHmmss" archiveOldFileOnStartup="false" maxArchiveDays="30" />
      <target name="EventLog" xsi:type="EventLog">
         <logLevel>Error</logLevel>
      </target>
      <target xsi:type="Console" name="lifetimeConsole" layout="${MicrosoftConsoleLayout}" />
   </targets>

   <rules>
      <logger name="*" minlevel="Trace" maxLevel="Warning" writeTo="allfile" />
      <logger name="Microsoft.*" maxLevel="Warning" final="true" />
      <logger name="System.Net.Http.*" maxlevel="Info" />
      <logger name="Microsoft.Hosting.Lifetime" minlevel="Info" writeTo="lifetimeConsole, ownFile-web" final="true" />
      <logger name="*" minlevel="Error" writeTo="EventLog" final="true" />
   </rules>
</nlog>

Logger is created like this:

var logger = LogManager.Setup().GetCurrentClassLogger();

Strange fact, it's running as expected if I add this to appsettings.json:

   "Logging": {
      "LogLevel": {
         "Default": "Information",
         "Microsoft": "Warning",
         "Microsoft.Hosting.Lifetime": "Information"
      },
      "EventLog": {
         "LogLevel": {
            "Default": "Error"
         }
      }
   },

And if I use my original nlog.config file:

<?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"
     >
   <extensions>
      <add assembly="NLog.Web.AspNetCore"/>
   </extensions>

   <targets>
           <target xsi:type="File" name="allfile" 
                   fileName="Backoffice_template.log"
                   layout="${longdate}|${event-properties:item=EventId_Id}|${uppercase:${level}}|${logger}|${message} ${exception:format=tostring} |action: ${aspnet-mvc-action} |user: ${aspnet-user-identity}" 
                   archiveEvery="Day"
                   encoding="utf-8"
                   archiveNumbering = "Date"
                   archiveDateFormat = "yyyyMMdd_HHmmss"
                   archiveOldFileOnStartup="false"
                   maxArchiveDays="30"
                   />

       <target xsi:type="Console" name="lifetimeConsole" layout="${MicrosoftConsoleLayout}" />
   </targets>

   <rules>
       <!--Do not change this value to set log level for BackOffice, instead change LogLevel.Default in appsettings.json -->
       <logger name="*" minlevel="Trace" writeTo="allfile" />
       <logger name="Microsoft.*" maxLevel="Warning" final="true" />
       <logger name="System.Net.Http.*" maxlevel="Info" final="true" />
       <logger name="Microsoft.Hosting.Lifetime" minlevel="Info" writeTo="lifetimeConsole" final="true" />
   </rules>
</nlog>

In summary, I have been asked to move the eventlog configuration from the appsettings.json to the NLog but I don't succeed to to it.

Answer 1

As stated on this page, when using Asp.Net Core (on Windows), there are some log providers that are automatically added, so trying to configure then in NLog is useless:

The default ASP.NET Core web app templates call WebApplication.CreateBuilder, which adds the following logging providers:

Console
Debug
EventSource
EventLog: Windows only