Although the accepted answer works in most cases, It has a few drawbacks.
- It only keeps 5 last logs.
- Log size is set to 1GB which is too large for most notepad applications to open.
- Since it locks the log file, it is not suitable for multi-threaded apps such as web applications.
- Since date is prefixed to the file name it is not convenient to use in windows
- It overwrites the log each time application re-starts which is again not suitable if you are planning to keep the logs.
- As mentioned in comments, it needs some modifications to make it work correctly in some cases.
Thus the little more extensive configuration. I created a class which makes logging a little easier. Obviously you can just pick the configuration part if you wish.
using log4net;
using log4net.Appender;
using log4net.Config;
using log4net.Core;
using log4net.Layout;
using log4net.Repository.Hierarchy;
using System;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Text;
using System.Web;
public enum LogType { Info, Debug, Warn, Error, Fatal };
public class Logger {
private const string LOG_NAMESPACE = "APP_NAME";
private const string LOG_FILENAME_PREFIX = @"D:\Logs\";
private static readonly Level LOG_LEVEL = Level.Debug;
private static readonly ILog log = LogManager.GetLogger(LOG_NAMESPACE);
#region static Logger()
// Static constructor is called automatically to initialize the class before the first instance is created or any static members are referenced
static Logger() {
Hierarchy hierarchy = (Hierarchy) LogManager.GetRepository();
hierarchy.Root.RemoveAllAppenders(); // Clear all previously added repositories.
hierarchy.Root.Level = LOG_LEVEL; // Set Log level
PatternLayout layout = new PatternLayout() { ConversionPattern = "%d{yyyy-MM-dd HH:mm:ss.fff} %4t %-5p %m%n" }; // Log line format: Include millisecond precision, thread ID, Log type,
layout.ActivateOptions(); // Apply Configuration
RollingFileAppender RFA = new RollingFileAppender();
RFA.Name = LOG_NAMESPACE; // Set name of appender
RFA.File = LOG_FILENAME_PREFIX + LOG_NAMESPACE; // Set file name prefix
RFA.LockingModel = new FileAppender.MinimalLock(); // Minimum lock time required, makes file available for reading
RFA.AppendToFile = true; // Do not overwrite existing logs, append to them.
RFA.DatePattern = ".yyyy.MM.dd'.log'"; // Add file extension here, to preserve the file extension
RFA.Encoding = Encoding.UTF8; // Set format of file to UTF8 for international characters.
RFA.CountDirection = 1; // Increment file name in bigger number is newest, instead of default backward.
RFA.MaximumFileSize = "100MB"; // Maximum size of file that I could open with common notepad applications
RFA.RollingStyle = RollingFileAppender.RollingMode.Composite; // Increment file names by both size and date.
RFA.StaticLogFileName = false;
RFA.MaxSizeRollBackups = -1; // Keep all log files, do not automatically delete any
RFA.PreserveLogFileNameExtension = true; // This plus extension added to DatePattern, causes to rolling size also work correctly
RFA.Layout = layout;
RFA.ActivateOptions(); // Apply Configuration
hierarchy.Root.AddAppender(RFA);
BasicConfigurator.Configure(hierarchy); // Apply Configuration
}
#endregion
#region public static int Log(...)
public static void Log(string Description, LogType logtype = LogType.Info) {
switch (logtype) {
case LogType.Debug:
log.Debug(Description);
break;
case LogType.Info:
log.Info(Description);
break;
case LogType.Warn:
log.Warn(Description);
break;
case LogType.Error:
log.Error(Description);
break;
case LogType.Fatal:
log.Fatal(Description);
break;
}
}
#endregion
#region public static int Log(...)
public static void Log(string Message, Exception ex) {
log.Fatal(Message, ex);
}
#endregion
}
And then to log messages and exceptions call it like following
Logger.Log("I was here", LogType.Debug);
Logger.Log("I am info message");
Logger.Log("An error", LogType.Error);
Logger.Log("An Exception", ex); // ex is of type Exception
Due to the weird way log4net adds rolling data to file name (added after file extension) files loose windows explorer association. To fix that .log was added to DatePattern instead. It will also correctly adds file increment before extension (maybe because of a bug) Tested on version 1.2.11.0
Notes:
- No external call for initialization is required, this will initialize on application start (or when you call Logger.Log for the first time
- You can move all class constants out to your own config file and make this class more generic and reusable.
- Note that no namespace is specified, this will make Logger class available in all namespaces.
- Log4net provides 5 methods to log messages which is a little inconvenient to remember. Thus
Logger.Log method by default uses info.
- An Unrelated note: If your application is running on a server or web, keep your log files off the OS drive and application folder.
