How to configure logging via log4net in an UWP App

Question

I have an UWP app that uses some of my libraries. Such libraries use log4net for logging purpose, and are shared across a number of projects, not only UWP.

I'd like to configure log4net via the usual confi section in the XML config file, but I cannot find a way to do this in an UWP project, since there isn't an app.config file.

Where should I put the following section?

<log4net>
    <appender name="Console" type="log4net.Appender.ConsoleAppender">
        <layout type="log4net.Layout.PatternLayout">
            <conversionPattern value="%date - %message%newline" />
        </layout>
    </appender>

    <appender name="RollingFile" type="log4net.Appender.RollingFileAppender">
        <file value="log\mylog.log" />
        <appendToFile value="true" />
        <maximumFileSize value="2000KB" />
        <maxSizeRollBackups value="20" />

        <layout type="log4net.Layout.PatternLayout">
            <conversionPattern value="%date - %message%newline" />
        </layout>
    </appender>

    <root>
        <level value="INFO" />
        <appender-ref ref="Console" />
        <appender-ref ref="RollingFile" />
    </root>
</log4net>

Thank you!

Answer 1

To complete pfx answer, if you are using netStandard, you will have to use Configure overloads with an additional parameter log4net.Repository.ILoggerRepository .

I haven't been able to use the ConsoleAppender and switch to the DebugAppender .

You cannot use relative path in UWP with RollingFileAppender since log4net will not have permission to create file in the install location of your application. I think it could work with a full path but I have seen some permissions issues (you should activate debug mode of log4net for this).

Finally, I also made a Custom Appender which writes file in the Local Storage of your application. Here is the code which should be enhanced for production use.

namespace AppWithLog4net
{
    public class LocalStorageFileAppender : log4net.Appender.TextWriterAppender
    {

        private Stream m_stream;

        public LocalStorageFileAppender() : base() {  }

        protected override void PrepareWriter()
        {
            IAsyncOperation<Windows.Storage.StorageFile> task = Windows.Storage.ApplicationData.Current.LocalCacheFolder.CreateFileAsync("localStorage.log", 
                                                                            Windows.Storage.CreationCollisionOption.GenerateUniqueName);
            Windows.Storage.StorageFile file = task.GetAwaiter().GetResult();
            m_stream = file.OpenStreamForWriteAsync().Result;

            QuietWriter = new log4net.Util.QuietTextWriter(new StreamWriter(m_stream, Encoding.UTF8), ErrorHandler);
            WriteHeader();
        }

        protected override void Reset()
        {
            m_stream.Dispose();
            m_stream = null;
            base.Reset();
        }
    }
}

With the following config file:

<log4net debug="true">
  <appender name="Console" type="log4net.Appender.DebugAppender">
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date - %message%newline" />
    </layout>
  </appender>

  <appender name="LocalStorageFile" type="AppWithLog4net.LocalStorageFileAppender, AppWithLog4net">
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date - %message%newline" />
    </layout>
  </appender>

  <root>
    <level value="INFO" />
    <appender-ref ref="Console" />
    <appender-ref ref="LocalStorageFile" />
  </root>
</log4net>

Answer 2

Because there is no App.config file, you are going to have to configure Log4net programmatically.

You can store the settings in a local file (or embedded resource) and read these at application startup; reference: Create and read a local file .

Log4net 's XmlConfigurator class can accept these settings as a Stream , FileInfo or XmlElement via one of its Configure overloads.

log4net.Config.XmlConfigurator.Configure(XmlElement config);
log4net.Config.XmlConfigurator.Configure(Stream config);
log4net.Config.XmlConfigurator.Configure(FileInfo config);