Log4Net: How to specify FileAppender layout type from a library?

Question

I am using Log4Net's RollingLogFileAppender along with a custom layout class in my console application to print some metadata information in the header. I now want to package this custom layout class in a library and tell log4net to use it.

Previously I was successfully able to use the following appender config:

  <appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
    <threshold value="DEBUG />
    <file value="C:\Logs\MyConsoleApp.log"
          type="log4net.Util.PatternString" />
    <preserveLogFileNameExtension value="true" />
    <datePattern value="_yyyyMMdd" />
    <rollingStyle value="Date" />
    <appendToFile value="true" />
    <staticLogFileName value="false" />
    <layout type="MyConsoleApp.MyLogLayout">
      <conversionPattern value="%date{ISO8601}|%-5level|%message%newline" />
    </layout>
  </appender>

I then tried moving the MyLogLayout class into a library project "MyLibrary.MyLogLayout", imported it into MyConsoleApp, and tried updating my appender code as follows:

  <appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
    <threshold value="DEBUG />
    <file value="C:\Logs\MyConsoleApp.log"
          type="log4net.Util.PatternString" />
    <preserveLogFileNameExtension value="true" />
    <datePattern value="_yyyyMMdd" />
    <rollingStyle value="Date" />
    <appendToFile value="true" />
    <staticLogFileName value="false" />
    <layout type="MyLibrary.MyLogLayout">
      <conversionPattern value="%date{ISO8601}|%-5level|%message%newline" />
    </layout>
  </appender>

When trying to run it I get this error:

log4net:ERROR Failed to find type [MyLibrary.MyLogLayout]
System.TypeLoadException: Could not load type [MyLibrary.MyLogLayout]. Tried assembly [log4net, Version=1.2.15.0, Culture=neutral
, PublicKeyToken=669e0ddf0bb1aa2a] and all loaded assemblies
   at log4net.Util.SystemInfo.GetTypeFromString(Assembly relativeAssembly, Strin
g typeName, Boolean throwOnError, Boolean ignoreCase)
   at log4net.Util.SystemInfo.GetTypeFromString(String typeName, Boolean throwOn
Error, Boolean ignoreCase)
   at log4net.Repository.Hierarchy.XmlHierarchyConfigurator.CreateObjectFromXml(
XmlElement element, Type defaultTargetType, Type typeConstraint)
log4net:ERROR Failed to create object to set param: layout

I have double checked to make sure that the dll is in the same folder, and that the reference works as expected. What's weird is that if I create a class MyConsoleApp.MyLogLayoutChild that just inherits everything from MyLibrary.MyLogLayout and reference it everything works, however the main point of pushing this code into a library is so that I don't have to create a new class for every project I make, especially one that doesn't have any logic in it other than to inherit everything from a parent class.

Does log4net support loading custom types from a dll library or am I just doing something wrong?

Answer 1

It does not work because TypeLoader does not know where to find your class. You need to help it by specifying fully qualified name of type. Like

<layout type="MyLibrary.MyLogLayout, MyLibrary, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">