log4net MemoryAppender not working

Question

I'm using log4net to log in my app. My FileAppender is working fine, but I'm having problems with MemoryAppender.

Here is my config file.

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
        <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
    </configSections>
<log4net>
<appender name="LogFileAppender" type="log4net.Appender.FileAppender">
  <param name="File" value="Envision.log" />
  <param name="AppendToFile" value="true" />
  <layout type="log4net.Layout.PatternLayout">
    <param name="Header" value="" />
    <param name="Footer" value="" />
    <param name="ConversionPattern" value="%d [%t] %-5p %m%n" />
  </layout>
</appender>
<appender name="MemoryAppender" type="log4net.Appender.MemoryAppender">

</appender>
<root>
  <level value="ALL" />
  <appender-ref ref="LogFileAppender" />
  <appender-ref ref="MemoryAppender" />
</root>
</log4net>
</configuration>

I use this code to setup the config file.

FileInfo file = new FileInfo(configPath);
log4net.Config.XmlConfigurator.Configure(file);
file = null;

Like I said, the FileAppender works great. But I can't seem to get any events. I've tried using something like this to get the MemoryAppender.

Hierarchy hierarchy = LogManager.GetRepository() as Hierarchy;
MemoryAppender mappender = hierarchy.Root.GetAppender("MemoryAppender") as MemoryAppender;

I've tried using:

var events = mappender.GetEvents()

after logging something, and events is always empty. I've tried setting up the FileAppender and MemoryAppender in code instead of using the config file, and I get the same, the FileAppender works fine, but can't seem to get any events from MemoryAppender. Curious if I'm understanding MemoryAppender right? I also tried setting up a thread that loops checking for the GetEvents to not be empty, and while logging away it always comes back empty. I've tried setting the Threshold to Core.Level.All on the MemoryAppender but that did not change anything.

Thanks for any direction. I've looked around, and from the sites I've seen, I can't tell what I'm doing different.

Even something as simple as this does not work. events length is always zero;

public partial class MainWindow : Window {
    public MainWindow() {
        InitializeComponent();

        MemoryAppender appender = new MemoryAppender();
        ILog logger = LogManager.GetLogger("foo");
        BasicConfigurator.Configure(appender);

        logger.Error("Should work");
        var events = appender.GetEvents();
    }
}

Answer 1

I adapted CZahrobsky's answer. Had to tweak slightly, since my class cannot have static logger by design.

Class under test has the log field declared like:

private ILog Logger = Log4netFactory.GetLogger(typeof(MyClass));

In the GetMemLog logic I have to first create an instance of MyClass and change the logField look up to getField by name 'Logger' and BindingFlags.Instance instead of BindingFlags.Static

//create an instance of the class
var myObject = new MyClass(context);

var memoryLog = new MemoryAppender();
ILog appendableLog = LogManager.GetLogger(typeof(JobQueue).Assembly, typeof(MyClass));
var repository = (log4net.Repository.Hierarchy.Hierarchy)appendableLog.Logger.Repository;
repository.Root.AddAppender(memoryLog);
var logField = typeof(MyClass).GetField("Logger", BindingFlags.NonPublic | BindingFlags.Instance);

if (logField != null)
{
    //set logfield property value for the instance
    logField.SetValue(myObject, appendableLog);
}

Examples on SetValue() for PropertyInfo is here

Answer 2

The simple sample code you posted works fine for me using log4net 1.2.10.0.

I would recommend downloading the source and stepping through it in a debugger. It may seem a little daunting at first, but you get used to their code pretty quickly and it's not hard to follow. I've done this many times when I had problems with custom constraints and appenders. It really helps solve problems quickly and gives you a much better understanding of how log4net works.

Answer 3

I used Ralph's code above in my unit testing:

using log4net;
using log4net.Appender;
// ...
internal static MemoryAppender GetMemoLog<T>() where T: class 
{
    var memoLog = new MemoryAppender();
    ILog appendableLog = LogManager.GetLogger(typeof(T).Assembly, typeof(T));
    var repository = (log4net.Repository.Hierarchy.Hierarchy)appendableLog.Logger.Repository;
    repository.Root.AddAppender(memoLog);            
    var logField = typeof(T).GetField("Log", BindingFlags.Static | BindingFlags.NonPublic);
    if (logField != null) logField.SetValue(null, appendableLog);
    return memoLog;
}

This assumes you have a private static Log field on your class:

private static readonly ILog Log = LogManager.GetLogger(typeof(MyClass));

So, in the test, it's just:

var memoLog = GetMemoLog<MyClass>(); 
// followed by test logic, and then... 
var events = memoLog.GetEvents();

Answer 4

For those that need it, here's how to do it programmatically in C#:

var memoryAppender = new MemoryAppender();
var repository = (log4net.Repository.Hierarchy.Hierarchy)LogManager.GetRepository();
repository.Root.AddAppender(memoryAppender);
var events = memoryAppender.GetEvents();

Answer 5

I figured it out. I was using the Compact Framework .dll by mistake. Once I realized that I switched to the .net 2.0 version, which caused a problem with log4net namespace not being found, so I did a search on that and realized I needed to change my .net Framework 4 client Profile to .net Framework 4. I'm now getting the events as expected.