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Logging display and WPF

, 12 Oct 2009 CPOL
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Logging display and WPF

A question appeared over on the CodeProject forums today about binding the output from log4net into WPF. The question asked was:

“I'm trying to use Log4net to log messages within my application. I'm adding a WPF window and want to stream the messages to the window. Log4net provides a TextWriterAppender that takes a StringWriter and writes logged events to the StringWriter, flushing it after each event. I want to simply connect the output of the StringWriter as the Text property on a TextBox. When I started this, it seemed simple and obvious – now I'm less sure. Ideally, I would simply like to bind the StringWriter to the TextBox, but haven't found the incantation.

The basic problem is that the StringWriter doesn't provide something like the INotifyPropertyChanged event to trigger code output a new log message (unless there is something behind the scenes I haven't found).

I've see many examples of binding, all of which seem to presume that I have control over the writer itself. Am I missing something simple (I hope), or is this really not that straightforward.”

This is a very good question, so I thought I'd knock together a quick sample application to demonstrate how to do this. The first thing to remember is that log4net allows you to create your own appenders and use them in your application. The second thing to remember is that you need to hook INotifyPropertyChanged into the mechanism. To that end, I created the following appender:

namespace log4netSample.Logging
  using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Text;
  using log4net.Appender;
  using System.ComponentModel;
  using System.IO;
  using System.Globalization;
  using log4net;
  using log4net.Core;

  /// <span class="code-SummaryComment"><summary>

Whenever a new message is appended, the Notification is updated and the PropertyChangedEventHandler is called to notify the calling application that the binding has been updated. In order to use this appender, you need to hook it into your configuration:

<?xml version="1.0" encoding="utf-8" ?>
    <section name="log4net"
      type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
    <add key="log4net.Internal.Debug" value="false"/>
    <trace autoflush="true">
        <add name="textWriterTraceListener"
    <appender name="NotifyAppender" type="log4netSample.Logging.NotifyAppender" >
      <layout type="log4net.Layout.PatternLayout">
        <param name="Header" value="[Header]\r\n" />
        <param name="Footer" value="[Footer]\r\n" />
        <param name="ConversionPattern" value="%d [%t] %-5p %c %m%n" />

      <level value="ALL" />
      <appender-ref ref="NotifyAppender" />

Note that you might want to add the following line into your AssemblyInfo.cs file:

[assembly: log4net.Config.XmlConfigurator(Watch=true)]

I find the following class really helpful when logging:

namespace log4netSample.Logging
  using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Text;
  using log4net;
  using log4net.Config;
  using log4net.Appender;
  using log4net.Repository.Hierarchy;

  public enum LogLevel
    Debug = 0,
    Error = 1,
    Fatal = 2,
    Info = 3,
    Warning = 4
  /// <span class="code-SummaryComment"><summary>

It’s a simple matter then to do something like:

Log.Write(LogLevel.Info, “This is my message”);

If you download the attached sample, you'll get to see the whole application running in all its glory, and you can see how updating the log results in the output being updated. Don't forget to rename the .doc file to .zip when you save it.


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


About the Author

Pete O'Hanlon
United Kingdom United Kingdom
A developer for over 30 years, I've been lucky enough to write articles and applications for Code Project as well as the Intel Ultimate Coder - Going Perceptual challenge. I live in the North East of England with 2 wonderful daughters and a wonderful wife.

I am not the Stig, but I do wish I had Lotus Tuned Suspension.

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Comments and Discussions

GeneralThank you Pin
Oceanator Framewurk16-Dec-14 10:20
memberOceanator Framewurk16-Dec-14 10:20 
BugDownload not working Pin
Marco Bertschi14-Jan-14 1:11
professionalMarco Bertschi14-Jan-14 1:11 
GeneralRe: Download not working Pin
Pete O'Hanlon14-Jan-14 1:41
protectorPete O'Hanlon14-Jan-14 1:41 
GeneralRe: Download not working Pin
Marco Bertschi14-Jan-14 2:09
professionalMarco Bertschi14-Jan-14 2:09 
QuestionExactly what I need Pin
Marco Bertschi14-Jan-14 1:09
professionalMarco Bertschi14-Jan-14 1:09 
GeneralMy vote of 5 Pin
Edo Tzumer20-May-13 3:12
professionalEdo Tzumer20-May-13 3:12 
QuestionLogging from a different thread Pin
Adrian Arsene28-Oct-12 2:31
memberAdrian Arsene28-Oct-12 2:31 
AnswerRe: Logging from a different thread Pin
Pete O'Hanlon29-Oct-12 7:51
protectorPete O'Hanlon29-Oct-12 7:51 
GeneralRe: Logging from a different thread Pin
Adrian Arsene30-Oct-12 21:50
memberAdrian Arsene30-Oct-12 21:50 

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