Can You Configure Log4Net in Code Instead of Using a Config File

Can you configure log4net in code instead of using a config file?

FINAL SOLUTION:₁

For anyone who may stumble upon this in the future, here is what I did. I made the static class below:

using log4net;
using log4net.Repository.Hierarchy;
using log4net.Core;
using log4net.Appender;
using log4net.Layout;

namespace Spectrum.Logging
{
    public class Logger
    {
        public static void Setup()
        {
            Hierarchy hierarchy = (Hierarchy)LogManager.GetRepository();

            PatternLayout patternLayout = new PatternLayout();
            patternLayout.ConversionPattern = "%date [%thread] %-5level %logger - %message%newline";
            patternLayout.ActivateOptions();

            RollingFileAppender roller = new RollingFileAppender();
            roller.AppendToFile = false;
            roller.File = @"Logs\EventLog.txt";
            roller.Layout = patternLayout;
            roller.MaxSizeRollBackups = 5;
            roller.MaximumFileSize = "1GB";
            roller.RollingStyle = RollingFileAppender.RollingMode.Size;
            roller.StaticLogFileName = true;            
            roller.ActivateOptions();
            hierarchy.Root.AddAppender(roller);

            MemoryAppender memory = new MemoryAppender();
            memory.ActivateOptions();
            hierarchy.Root.AddAppender(memory);

            hierarchy.Root.Level = Level.Info;
            hierarchy.Configured = true;
        }
    }
}

And then all I had to do was replace the code where I called the XML file with the following call:

//XmlConfigurator.Configure(new FileInfo("app.config")); // Not needed anymore
Logger.Setup();

^{1_{(this answer was edited into the question by the OP, I took the liberty to make it a community answer, see here why)}}

How to configure log4net programmatically from scratch (no config)

One way I've done this in the past is to include the configuration file as an embedded resource, and just used log4net.Config.Configure(Stream).

That way, I could use the configuration syntax I was familiar with, and didn't have to worry about getting a file deployed.

Configuring log4net programmatically, but extra logging going to console

According to the log4net configuration page, calling BasicConfigurator.Configure() method will "Set up a simple configuration that logs on the console."

Seeing as you've configured things programmatically to write to a file, no need to include the line:

BasicConfigurator.Configure();

Enable file logging for log4net from code instead of from configuration

I always use the code below to configure log4net from code. Works great!

Hierarchy hierarchy = (Hierarchy)LogManager.GetRepository();
hierarchy.Root.RemoveAllAppenders(); /*Remove any other appenders*/

FileAppender fileAppender = new FileAppender();
fileAppender.AppendToFile = true;
fileAppender.LockingModel = new FileAppender.MinimalLock();
fileAppender.File = Server.MapPath("/") + "log.txt";
PatternLayout pl = new PatternLayout();
pl.ConversionPattern = "%d [%2%t] %-5p [%-10c]   %m%n%n";
pl.ActivateOptions();
fileAppender.Layout = pl;
fileAppender.ActivateOptions();

log4net.Config.BasicConfigurator.Configure(fileAppender);

//Test logger
ILog log =LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
log.Debug("Testing!");

Why is the log4net config file code causing my C# Windows service to not start but the same thing implemented in code starts the service?

As for what you have written in you app.config file i can assume that you haven't added the configSections with a new section named as Log4net.
So, what you can do is make the following changes to make the Log4net work.

1st app.config:

Make changes from this

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<startup> 
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.1" />
</startup>
<log4net>
<appender name="TestAppender" type="log4net.Appender.RollingFileAppender" >
  <file value="C:\log\impersonationlog_JamochaService.log" />
  <encoding value="utf-8" />
  <appendToFile value="true" />
  <rollingStyle value="Date" />
  <!--<rollingStyle value="Size" />
  <maxSizeRollBackups value="5" />
  <maximumFileSize value="5MB" />
  <staticLogFileName value="true" />-->
  <layout type="log4net.Layout.PatternLayout">
    <conversionPattern value="%date %level [%thread] %type.%method - 
 %message%n" />
  </layout>
  </appender>
  <root>
  <level value="All" />
  <!-- If the following line is not included the log file 
  will not be created even if log4net is configured with this file. -->
  <appender-ref ref="TestAppender" />
</root>
</log4net>
</configuration>

to this:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
<section name="log4net" 
type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"></section>
</configSections>
<startup> 
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.1" />
</startup>  
<log4net>
<appender name="TestAppender" type="log4net.Appender.RollingFileAppender" >
  <file value="C:\log\impersonationlog_JamochaService.log" />
  <encoding value="utf-8" />
  <appendToFile value="true" />
  <rollingStyle value="Date" />
  <!--<rollingStyle value="Size" />
  <maxSizeRollBackups value="5" />
  <maximumFileSize value="5MB" />
  <staticLogFileName value="true" />-->
  <layout type="log4net.Layout.PatternLayout">
    <conversionPattern value="%date %level [%thread] %type.%method - 
%message%n" />
  </layout>
</appender>
<root>
  <level value="All" />
  <!-- If the following line is not included the log file 
  will not be created even if log4net is configured with this file. -->
  <appender-ref ref="TestAppender" />
</root>
</log4net>
</configuration>

Then in the class in which you want to use create an global object of the Log4net as:

ILog log = LogManager.GetLogger(typeof(yourclassname));

and then in the class just use it like:

log.info("hi i am a log");

Hope this helps.

why log4net config file is not being read

I worked this out, I don't know if it's the proper fix - and I have no idea why it worked once in VS - but I think it's just that the config file is not configured properly.

Firstly, since there is a declaration of the file in AssemblyInfo.cs there is no need for log4net.Config.XmlConfigurator.Configure();.

Secondly, I simply had to add both appenders to the root tag:

<root>
 <level value="DEBUG" />
 <appender-ref ref="A1" />
 <appender-ref ref="RollingFile" />
</root>

And that's it. VS outputs on console as well as file, and exe outputs to file.

How to get Log4Net to use app.config

The assembly attribute must be in the MainApp project, not in the Utilities project.

As it says in the documentation for assembly attributes

Therefore if you use configuration attributes you must invoke log4net
to allow it to read the attributes. A simple call to
LogManager.GetLogger will cause the attributes on the calling assembly
to be read and processed. Therefore it is imperative to make a logging
call as early as possible during the application start-up, and
certainly before any external assemblies have been loaded and invoked.

Simplest correct way to configure log4net for a .Net Core 3.1 application

Editing my answer a little to be clear that Core does NOT include a normal file logger out of the box. My bad. (as of 5/19/2020)

I would recommend using the logging extensions from Microsoft instead of log4net, but this should do for you. Core now comes with a logger and it's pretty nice and plugs in easy for DI, and uses appsettings.json. I can provide a sample of that too if you want. But here's log4net basic example.

Sample console app that loads config from a file (file set to Copy Always)

using log4net.Repository;
using System;
using System.IO;
using System.Reflection;

namespace ConsoleApp1Core
{
    class Program
    {
        private static readonly log4net.ILog log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

        static void Main(string[] args)
        {
            try
            {

                ILoggerRepository repository = log4net.LogManager.GetRepository(Assembly.GetCallingAssembly());

                var fileInfo = new FileInfo(@"log4net.config");

                log4net.Config.XmlConfigurator.Configure(repository, fileInfo);

                log.Info("test");

                Console.WriteLine("press any key");
                Console.ReadLine();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                Console.WriteLine("Press any key to exit");
                Console.ReadLine();
            }
        }
    }
}

Can You Configure Log4Net in Code Instead of Using a Config File