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

Question

I understand why log4net uses app.config files for setting up logging - so you can easily change how information is logged without needing to recompile your cod

Answer 1

The accepted answer works after I found two caveats:

• It was not working for me at first, but after using a full absolue path for the roller.File property, it started work.
• I had to use this in F# (in a fsx script), so had some issues when converting it from C#. If you're interested in the end result (including a way to download log4net nuget package), see below:

nuget_log4net.fsx:

#!/usr/bin/env fsharpi

open System
open System.IO
open System.Net

#r "System.IO.Compression.FileSystem"
open System.IO.Compression

type DummyTypeForLog4Net () =
    do ()

module NetTools =

    let DownloadNuget (packageId: string, packageVersion: string) =
    use webClient = new WebClient()
    let fileName = sprintf "%s.%s.nupkg" packageId packageVersion

    let pathToUncompressTo = Path.Combine("packages", packageId)
    if (Directory.Exists(pathToUncompressTo)) then
        Directory.Delete(pathToUncompressTo, true)
    Directory.CreateDirectory(pathToUncompressTo) |> ignore
    let fileToDownload = Path.Combine(pathToUncompressTo, fileName)

    let nugetDownloadUri = Uri (sprintf "https://www.nuget.org/api/v2/package/%s/%s" packageId packageVersion)
    webClient.DownloadFile (nugetDownloadUri, fileToDownload)

    ZipFile.ExtractToDirectory(fileToDownload, pathToUncompressTo)

let packageId = "log4net"
let packageVersion = "2.0.5"
NetTools.DownloadNuget(packageId, packageVersion)

let currentDirectory = Directory.GetCurrentDirectory()

// https://stackoverflow.com/a/19538654/6503091
#r "packages/log4net/lib/net45-full/log4net"

open log4net
open log4net.Repository.Hierarchy
open log4net.Core
open log4net.Appender
open log4net.Layout
open log4net.Config

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

let roller = RollingFileAppender()
roller.AppendToFile <- true
roller.File <- Path.Combine(currentDirectory, "someLog.txt")
roller.Layout <- patternLayout
roller.MaxSizeRollBackups <- 5
roller.MaximumFileSize <- "1GB"
roller.RollingStyle <- RollingFileAppender.RollingMode.Size
roller.StaticLogFileName <- true
roller.ActivateOptions ()

let hierarchy = box (LogManager.GetRepository()) :?> Hierarchy
hierarchy.Root.AddAppender (roller)

hierarchy.Root.Level <- Level.Info
hierarchy.Configured <- true
BasicConfigurator.Configure(hierarchy)

let aType = typedefof<DummyTypeForLog4Net>
let logger = LogManager.GetLogger(aType)

logger.Error(new Exception("exception test"))

Answer 2

You can also escape XML completely, I wrote a sample with minimal programmatic configuration here.

In a nutshell, here is what you need

var tracer = new TraceAppender();
var hierarchy = (Hierarchy)LogManager.GetRepository();
hierarchy.Root.AddAppender(tracer);
var patternLayout = new PatternLayout {ConversionPattern = "%m%n"};
patternLayout.ActivateOptions();
tracer.Layout = patternLayout;
hierarchy.Configured = true;

Answer 3

For those who don't want to add appender to Root logger, but to current/other logger:

//somewhere you've made a logger
var logger = LogManager.GetLogger("MyLogger");

// now add appender to it
var appender = BuildMyAppender();
((log4net.Repository.Hierarchy.Logger)logger).AddAppender(appender);

logger.Debug("MyLogger with MyAppender must work now");

// and remove it later if this code executed multiple times (loggers are cached, so you'll get logger with your appender attached next time "MyLogger")
((log4net.Repository.Hierarchy.Logger)logger).RemoveAppender(sbAppender);

Answer 4

Yes, you can configure log4net by calling:

log4net.Config.XmlConfigurator.Configure(XmlElement element)

See the log4net documentation.

Answer 5

Alternatively you could create a custom attribute that inherits from log4net.Config.ConfiguratorAttribute and hard-code you configuration there:

using log4net.Appender;
using log4net.Config;
using log4net.Core;
using log4net.Layout;
using log4net.Repository;
using log4net.Repository.Hierarchy;
using System;
using System.Reflection;

namespace ConsoleApplication1
{
    [AttributeUsage(AttributeTargets.Assembly)]
    public class MyConfiguratorAttribute : ConfiguratorAttribute
    {
        public MyConfiguratorAttribute()
            : base(0)
        {
        }

        public override void Configure(Assembly sourceAssembly, ILoggerRepository targetRepository)
        {
            var hierarchy = (Hierarchy)targetRepository;
            var patternLayout = new PatternLayout();
            patternLayout.ConversionPattern = "%date [%thread] %-5level %logger - %message%newline";
            patternLayout.ActivateOptions();

            var 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);

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

Then add the following to a .cs file:

[assembly: ConsoleApplication1.MyConfigurator]

Answer 6

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();

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