C# – How to configure and enable log4net for a stand-alone class library assembly

clog4netnet

Background

I am writing a class library assembly in C# .NET 3.5 which is used for integration with other applications including third-party Commercial-Off-The-Shelf (COTS) tools. Therefore, sometimes this class library will be called by applications (EXEs) that I control while other times it will be called by other DLLs or applications that I do not control.

Assumptions

I am using C# 3.0, .NET 3.5 SP1, and Visual Studio 2008 SP1
I am using log4net 1.2.10.0 or greater

Constraints

Any solution must:

Allow for the class library to enable and configure logging via it's own configuration file, if the calling application does not configure log4net.
Allow for the class library to enable and configuring logging via the calling applications configuration, if it specifies log4net information

Allow for the class library to enable and configuring logging using it's own configuration file at all times.

Problem

When my stand-alone class library is called by a DLL or application that I do not control (such as a third-party COTS tool) and which doesn't specify log4net configuration information, my class library is unable to do any of it's logging.

Question

How do you configure and enable log4net for a stand-alone class library assembly so that it will log regardless if the calling application provides log4net configuration?

Best Answer

You can probably code something around the XmlConfigurator class:

public static class MyLogManager
{
    // for illustration, you should configure this somewhere else...
    private static string configFile = @"path\to\log4net.config";

    public static ILog GetLogger(Type type)
    {
        if(log4net.LogManager.GetCurrentLoggers().Length == 0)
        {
            // load logger config with XmlConfigurator
            log4net.Config.XmlConfigurator.Configure(configFile);
        }
        return LogManager.GetLogger(type);
    }
}

Then in your classes, instead of:

private static readonly ILog log = LogManager.GetLogger(typeof(MyApp));

Use:

private static readonly ILog log = MyLogManager.GetLogger(typeof(MyApp));

Of course, it would be preferable to make this class a service and dynamically configure it with the IoC container of your choice, but you get the idea?

EDIT: Fixed Count() problem pointed out in comments.

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Add the following values to

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Fusion
Add:
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DWORD EnableLog set value to 1
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Make sure you include the backslash after the folder name and that the Folder exists.

You need to restart the program that you're running to force it to read those registry settings.

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C# – How to convert a byte array to a hexadecimal string, and vice versa

You can use Convert.ToHexString starting with .NET 5.
There's also a method for the reverse operation: Convert.FromHexString.

For older versions of .NET you can either use:

public static string ByteArrayToString(byte[] ba)
{
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