How to use log4net in Asp.net core 2.0

Question

I configure log4net in my asp.net core 2.0 application as mentioned in this article LINK

program.cs

public static void Main(string[] args)
{
    var logRepository = LogManager.GetRepository(Assembly.GetEntryAssembly());
    XmlConfigurator.Configure(logRepository, new FileInfo("log4net.config"));

    BuildWebHost(args).Run();
}

HomeController

public class HomeController : Controller
{
    private static readonly log4net.ILog log = log4net.LogManager.GetLogger(typeof(HomeController));

    public IActionResult Error()
    {
        log.Info("Hello logging world!");
        return View(new ErrorViewModel { RequestId = Activity.Current?.Id ?? HttpContext.TraceIdentifier });
    }
}

log4net.config

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <log4net>
    <root>
      <level value="ALL" />
      <appender-ref ref="RollingFile" />
    </root>
    <appender name="RollingFile" type="log4net.Appender.FileAppender">
      <file value="‪C:\Temp\app.log" /> 
      <layout type="log4net.Layout.PatternLayout">
        <conversionPattern value="%-5p %d{hh:mm:ss} %message%newline" />
      </layout>
    </appender>
  </log4net>
</configuration>

Unlucky!, I didn't see any file generated in ‪C:\Temp\app.log directory. What would be the mistake? how to configure log4net for asp.net core 2.0?

Solution 1

I am successfully able to log a file using the following code

public static void Main(string[] args)
{
    XmlDocument log4netConfig = new XmlDocument();
    log4netConfig.Load(File.OpenRead("log4net.config"));
    var repo = log4net.LogManager.CreateRepository(Assembly.GetEntryAssembly(),
               typeof(log4net.Repository.Hierarchy.Hierarchy));
    log4net.Config.XmlConfigurator.Configure(repo, log4netConfig["log4net"]);

    BuildWebHost(args).Run();
}

log4net.config in website root

<?xml version="1.0" encoding="utf-8" ?>
<log4net>
  <appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
    <lockingModel type="log4net.Appender.FileAppender+MinimalLock"/>
    <file value="C:\Temp\" />
    <datePattern value="yyyy-MM-dd.'txt'"/>
    <staticLogFileName value="false"/>
    <appendToFile value="true"/>
    <rollingStyle value="Date"/>
    <maxSizeRollBackups value="100"/>
    <maximumFileSize value="15MB"/>
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date [%thread] %-5level App  %newline %message %newline %newline"/>
    </layout>
  </appender>
    <root>
      <level value="ALL"/>
      <appender-ref ref="RollingLogFileAppender"/>
    </root>
</log4net>

Solution 2

There is a third-party log4net adapter for the ASP.NET Core logging interface.

Only thing you need to do is pass the ILoggerFactory to your Startup class, then call

loggerFactory.AddLog4Net();

and have a config in place. So you don't have to write any boiler-plate code.

More info here

Solution 3

Still looking for a solution? I got mine from this link .

All I had to do was add this two lines of code at the top of "public static void Main" method in the "program class".

 var logRepo = LogManager.GetRepository(Assembly.GetEntryAssembly());
 XmlConfigurator.Configure(logRepo, new FileInfo("log4net.config"));

Yes, you have to add:

1. Microsoft.Extensions.Logging.Log4Net.AspNetCore using NuGet.
2. A text file with the name of log4net.config and change the property(Copy to Output Directory) of the file to "Copy if Newer" or "Copy always".

You can also configure your asp.net core application in such a way that everything that is logged in the output console will be logged in the appender of your choice. You can also download this example code from github and see how i configured it.

Solution 4

You need to install the Microsoft.Extensions.Logging.Log4Net.AspNetCore NuGet package and add a log4net.config-file to your application. Then this should work:

public class Program
{
    private readonly ILogger<Program> logger;

    public Program()
    {
        var services = new ServiceCollection()
            .AddLogging(logBuilder => logBuilder.SetMinimumLevel(LogLevel.Debug))
            .BuildServiceProvider();


        logger = services.GetService<ILoggerFactory>()
            .AddLog4Net()
            .CreateLogger<Program>();
    }

    static void Main(string[] args)
    {
        Program program = new Program();

        program.Run();

        Console.WriteLine("\n\nPress any key to continue...");
        Console.ReadKey();
    }

    private void Run()
    {
        logger.LogInformation("Logging is working");
    }
}

Solution 5

Following on Irfan's answer, I have the following XML configuration on OSX with .NET Core 2.1.300 which correctly logs and appends to a ./log folder and also to the console. Note the log4net.config must exist in the solution root (whereas in my case, my app root is a subfolder).

<?xml version="1.0" encoding="utf-8" ?>
<log4net>
  <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender" >
      <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date %-5level %logger - %message%newline" />
      </layout>
  </appender>
  <appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
    <lockingModel type="log4net.Appender.FileAppender+MinimalLock"/>
    <file value="logs/" />
    <datePattern value="yyyy-MM-dd.'txt'"/>
    <staticLogFileName value="false"/>
    <appendToFile value="true"/>
    <rollingStyle value="Date"/>
    <maxSizeRollBackups value="100"/>
    <maximumFileSize value="15MB"/>
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date [%thread] %-5level App  %newline %message %newline %newline"/>
    </layout>
  </appender>
    <root>
      <level value="ALL"/>
      <appender-ref ref="RollingLogFileAppender"/>
      <appender-ref ref="ConsoleAppender"/>
    </root>
</log4net>

Another note, the traditional way of setting the XML up within app.config did not work:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <configSections>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
  </configSections>
  <log4net> ...

For some reason, the log4net node was not found when accessing the XMLDocument via log4netConfig["log4net"].

View more solutions

Comments

[The Muffin Man]

The root gets setup properly, but any child loggers have null for level, and don't have an appenders set up.

[Irfan Ashraf]

I am unaware of child loggers, can you share code and example so I can include in my answer.

[Shane Kenyon]

Caveat, the debugger looks for the file in the sub-folder, not the root.

[Przemek]

Ok, but how do you use this logger? I did not find examples on usage in the provided link eaither. Examples?

[Jan Muncinsky]

@Przemek. Once you do this, then inject ILogger or ILogger<T> where ever you need and all calls will be forwarded to log4net implementation. docs.microsoft.com/en-us/aspnet/core/fundamentals/logging/…

[Radek Strugalski]

Still not working (refering to ASP.NET Core 2.1 framework). Log file is not created. log4.net.config is read, but appenders do not seem to be created (log has empty list of Appenders). XmlConfigurator is called. log4net.configis exactly as in the original post. Any ideas?

[techjunkie]

You can look at the entire implementation at techjunkieblog.com/2019/08/…

[Ranvijay Singh]

Does EventLogAppender support is provided for .NetCore3.0 in Log4Net?

[David Thielen]

Is this still the best (and needed) solution on .NET Core 3.0?

[ckapilla]

worked great for me; no need to mess with ServiceCollections as shown in the next answer.

[red888]

how do you have multiple log4net config files base on dev or prod and switch between them?

[ahsant]

Remove <configuration> section from log4net.config. If you are using existing log4net.config

[WillC]

For .Net Core 3.1, the connectionType has apparently changed to: <connectionType value="Microsoft.Data.SqlClient.SqlConnection, Microsoft.Data.SqlClient, Version=1.0.0.0,Culture=neutral,PublicKeyToken=23ec7fc2d6eaa‌​4a5"/>

[WillC]

This worked for me. See Darios answer on: stackoverflow.com/questions/60897550/…