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Mini Drop-in Replacement for log4net

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4.83 (32 votes)
4 May 2012CPOL
Mini drop-in replacement for log4net


This is a simple 8KB drop in replacement for complex 198KB Log4net that’s a 96% size reduction. Strange that after looking on the web for a logging solution that fitted my requirements, I couldn't find one.


I have been using log4net for the past 7 years and it is undoubtedly the de-facto standard for logging in the .NET Framework environment. I am also a follower of the minimalistic philosophy, and to this end, I have created a drop in replacement for log4net which is smaller and a lot less complex.

This was done mostly for the reason of size restrictions in a project, i.e., minimizing the deployment footprint of the app and also as a review exercise.

Obviously, it does not have the feature set of the original, but 99% of the time you don't need it in my experience.

What You Get

So what this mini log4net does for you is the following:

  • 200 lines of code
  • Drop-in replace log4net
  • Threaded logger: no blocking of main code to log messages
  • Write to a text files only (you can add other destinations yourself if you need it)
  • Size limit log files and roll the file names with a count number
  • Date roll log files: new file for each new day
  • Simple single method configuration: no XML configuration files
  • Ability to log method name: *performance hit

Using the Code

You can pretty much forget about any changes to your code because it will work as is.

public class someclass
    log4net.ILog _log = LogManager.GetLogger(typeof(someclass));

    public void Method()
       _log.Debug("hello world!");

The only changes to your code would be in the startup routine for your application where you configure the logger, this would be where you use log4net's DOMConfigurator methods and the XML configuration files.

public static void Main()
              //where to put the logs : folders will be automatically created
               500,// limit the file sizes to 500kb, 0 = no limiting
               false); // log method call names -> performance hit if enabled


Points of Interest

The code is pretty straightforward given it is only 200 lines long, but there is a couple of “gotchas” that I will point out here:

  • AppDomain.CurrentDomain.ProcessExit: For this function to work, you must set the thread IsBackground to True otherwise it will just ignore the process exit and continue the thread. This point took me around 4 hours and a lot of hassle to try to figure out.
  • Rolling filenames: If you look at the code for implementing the rolling functionality for file names, it’s simple and dirty but it works.
  • LOG format output: The log output format is hardcoded to my own preference but you can change it to what you like in the code.
  • Size limit: The size limitation for files is not exact but it does the job in the least lines of code and keeps the message contiguous, so you don’t have to open before and after files to see the messages.
  • Method names: If you set the showmethodnames in the Configuration function, the logger will output the method name for the function in the log file which is a great help for debugging code as it specifies the exact place of the message/error and you don’t have to do anything.

The only problem is the performance hit you get because the code does a stack trace and extracts the method name. I would not recommend using this in production code but then again if you don’t log that many messages, it doesn’t matter.


  • Initial release: 2010/12/07 
  • Update v1.1 : 2012/05/05
    • uses a timer instead of a thread
    • added Shutdown() for implicit closing of files
    • optimized string output


This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Mehdi Gholam
Architect -
United Kingdom United Kingdom
Mehdi first started programming when he was 8 on BBC+128k machine in 6512 processor language, after various hardware and software changes he eventually came across .net and c# which he has been using since v1.0.
He is formally educated as a system analyst Industrial engineer, but his programming passion continues.

* Mehdi is the 5th person to get 6 out of 7 Platinum's on Code-Project (13th Jan'12)
* Mehdi is the 3rd person to get 7 out of 7 Platinum's on Code-Project (26th Aug'16)

Comments and Discussions

QuestionnUnit problem Pin
SohailB17-Sep-11 0:30
memberSohailB17-Sep-11 0:30 
AnswerRe: nUnit problem Pin
Mehdi Gholam17-Sep-11 0:40
mveMehdi Gholam17-Sep-11 0:40 
GeneralRe: nUnit problem Pin
SohailB17-Sep-11 0:44
memberSohailB17-Sep-11 0:44 
GeneralRe: nUnit problem Pin
Mehdi Gholam17-Sep-11 0:48
mveMehdi Gholam17-Sep-11 0:48 
GeneralMy vote of 4 Pin
SatorArepoOperaRotas18-Jul-11 22:47
memberSatorArepoOperaRotas18-Jul-11 22:47 
QuestionUsing in web environment Pin
SatorArepoOperaRotas18-Jul-11 22:45
memberSatorArepoOperaRotas18-Jul-11 22:45 
AnswerRe: Using in web environment Pin
Mehdi Gholam18-Jul-11 22:55
mveMehdi Gholam18-Jul-11 22:55 
GeneralRe: Using in web environment Pin
SatorArepoOperaRotas19-Jul-11 0:03
memberSatorArepoOperaRotas19-Jul-11 0:03 
Here is my modified version that fit my needs: it appends datetime to filename and then compare current datetime with the one extracted from filename in order to change log file; I also added a LogVerbosity to set threshold logging message...

using System;
using System.Collections;
using System.IO;
using System.Text;
using System.Threading;
using System.Globalization;

namespace MyLogger
    public interface ILog
        void Debug(object msg, params object[] objs);
        void Error(object msg, params object[] objs);
        void Info(object msg, params object[] objs);
        void Warn(object msg, params object[] objs);
        void Fatal(object msg, params object[] objs);

    public enum LogVerbosity
        FATAL = 0,

    internal class FileLogger
        public static readonly FileLogger Instance = new FileLogger();

        private FileLogger()
            AppDomain.CurrentDomain.ProcessExit += new EventHandler(CurrentDomain_ProcessExit);
            AppDomain.CurrentDomain.DomainUnload += new EventHandler(CurrentDomain_ProcessExit);

            _worker = new Thread(new ThreadStart(Writer));
            _worker.IsBackground = true;

        private Thread _worker;
        private bool _working = true;
        private Queue _que = new Queue();
        private StreamWriter _output;
        private string _baseFilename;
        private string _filename;
        private int _sizeLimit = 0;
        private long _lastSize = 0;
        private DateTime _lastFileDate;
        private bool _showMethodName = false;
        private string _FilePath = "";

        private const string dateTimeFormat = "yyyy-MM-dd";

        private LogVerbosity _verbosity = LogVerbosity.DEBUG;

        public bool ShowMethodNames
            get { return _showMethodName; }

        public LogVerbosity Verbosity
            get { return _verbosity; }
            set { _verbosity = value; }

        public void Init(string filename, int sizelimitKB, bool showmethodnames, LogVerbosity verbosity)
            _showMethodName = showmethodnames;
            _sizeLimit = sizelimitKB;
            _baseFilename = filename;
            _filename = buildFilename();
            _verbosity = verbosity;
            // handle folder names as well -> create dir etc.
            _FilePath = Path.GetDirectoryName(filename);
            if (_FilePath != "")
                _FilePath = Directory.CreateDirectory(_FilePath).FullName;
                if (_FilePath.EndsWith("\\") == false)
                    _FilePath += "\\";
            _output = new StreamWriter(_filename, true);
            FileInfo fi = new FileInfo(_filename);
            _lastSize = fi.Length;
            _lastFileDate = fi.LastWriteTime;

        private string buildFilename()
            return Path.Combine(Path.GetDirectoryName(_baseFilename), string.Format("{0}_{1}{2}", Path.GetFileNameWithoutExtension(_baseFilename), DateTime.Today.ToString(dateTimeFormat), Path.GetExtension(_baseFilename)));

        private void shutdown()
            _working = false;

        void CurrentDomain_ProcessExit(object sender, EventArgs e)

        private void Writer()
            while (_working)
                while (_que.Count > 0)
                    object o = _que.Dequeue();
                    if (_output != null && o != null)
                        if (_sizeLimit > 0)
                            // implement size limited logs
                            // implement rolling logs
                            #region [  rolling size limit ]
                            _lastSize += ("" + o).Length;
                            if (_lastSize > _sizeLimit * 1000)
                                int count = 1;
                                while (File.Exists(_FilePath + Path.GetFileNameWithoutExtension(_filename) + "." + count.ToString("0000")))

                                    _FilePath +
                                    Path.GetFileNameWithoutExtension(_filename) +
                                    "." + count.ToString("0000"));
                                _output = new StreamWriter(_filename, true);
                                _lastSize = 0;

                        string fileDate = _filename.Substring(_filename.LastIndexOf('_') + 1, dateTimeFormat.Length);
                        DateTime fileDateFromName = DateTime.ParseExact(fileDate, dateTimeFormat, CultureInfo.InvariantCulture);

                        if (DateTime.Now.Subtract(_lastFileDate).Days > 0 || DateTime.Now.Subtract(fileDateFromName).Days > 0)
                            // implement date logs
                            #region [  rolling dates  ]
                            _filename = buildFilename();
                            _output = new StreamWriter(_filename, true);
                            _lastFileDate = DateTime.Now;
                            _lastSize = 0;

                if (_output != null)

        private string FormatLog(string log, string type, string meth, string msg, object[] objs)
            StringBuilder sb = new StringBuilder();

                "" + DateTime.Now.ToString("dd'/'MM'/'yyyy HH:mm:ss.fff") +
                "|" + log +
                "|" + Thread.CurrentThread.ManagedThreadId +
                "|" + type +
                "|" + meth +
                "| " + string.Format(msg, objs));

            return sb.ToString();

        public void Log(string logtype, string type, string meth, string msg, params object[] objs)
            _que.Enqueue(FormatLog(logtype, type, meth, msg, objs));

    internal class logger : ILog
        public logger(Type type)
            typename = type.Namespace + "." + type.Name;

        private string typename = "";

        private void log(string logtype, string msg, params object[] objs)
            string meth = "";
            if (FileLogger.Instance.ShowMethodNames)
                System.Diagnostics.StackTrace st = new System.Diagnostics.StackTrace(2);
                System.Diagnostics.StackFrame sf = st.GetFrame(0);
                meth = sf.GetMethod().Name;
            FileLogger.Instance.Log(logtype, typename, meth, msg, objs);

        #region ILog Members

        public void Debug(object msg, params object[] objs)
            if(FileLogger.Instance.Verbosity >= LogVerbosity.DEBUG)
                log("DEBUG", "" + msg, objs);

        public void Error(object msg, params object[] objs)
            if (FileLogger.Instance.Verbosity >= LogVerbosity.ERROR)
                log("ERROR", "" + msg, objs);

        public void Info(object msg, params object[] objs)
            if (FileLogger.Instance.Verbosity >= LogVerbosity.INFO)
                log("INFO", "" + msg, objs);

        public void Warn(object msg, params object[] objs)
            if (FileLogger.Instance.Verbosity >= LogVerbosity.WARNING)
                log("WARN", "" + msg, objs);

        public void Fatal(object msg, params object[] objs)
            if (FileLogger.Instance.Verbosity >= LogVerbosity.FATAL)
                log("FATAL", "" + msg, objs);

    public static class LogManager
        public static ILog GetLogger(Type obj)
            return new logger(obj);

        public static void Configure(string filename, int sizelimitKB, bool showmethodnames, LogVerbosity verbosity)
            FileLogger.Instance.Init(filename, sizelimitKB, showmethodnames, verbosity);


GeneralRe: Using in web environment Pin
Mehdi Gholam19-Jul-11 0:14
mveMehdi Gholam19-Jul-11 0:14 
QuestionDatabase Pin
Dirk_Strauss13-Jul-11 20:48
professionalDirk_Strauss13-Jul-11 20:48 
AnswerRe: Database Pin
Mehdi Gholam13-Jul-11 20:55
mveMehdi Gholam13-Jul-11 20:55 
Generalcomparison Pin
SohailB15-Dec-10 9:23
memberSohailB15-Dec-10 9:23 
GeneralRe: comparison Pin
Mehdi Gholam15-Dec-10 21:09
mveMehdi Gholam15-Dec-10 21:09 
GeneralRe: comparison Pin
dave.dolan5-May-12 18:10
memberdave.dolan5-May-12 18:10 

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Posted 13 Dec 2010

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