Multifile host based cofiguration for .Net
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Lib Updated Nuget command line and Elmah packages Jan 18, 2012
NConfig.Tests backward compatibility of proj files, add new files to 3.5 project Mar 10, 2017
NConfig backward compatibility of proj files, add new files to 3.5 project Mar 10, 2017
NuGet Version 1.1.22 Mar 5, 2017
NConfig.sln Removed all platform configurations except AnyCPU Dec 28, 2011
NuGet Publish.bat
NuGet.bat backward compatibility of proj files, add new files to 3.5 project Mar 10, 2017
nuget.config NuGet support: Mar 1, 2011


NConfig is a .Net library that allows using multi-file, host-based configurations in .Net

This is thing you are really missing during staged deployments and with developer dependent environments.


All Original Software is licensed under the MIT License (see LICENSE.txt) and does not apply to any other 3rd party tools, utilities or code which may be used to develop this application.

Please inform me if anyone is aware of any license violations that this code may be making.


The easiest way to build NConfig from source is to clone the git repository on GitHub and build the NConfig solution.

git clone git://

The solution file NConfig.sln is located in the root of the repo.

NuGet support

You can find NConfig in NuGet Gallery or just install it using VS NuGet Packages Manager.
Or just type Install-Package NConfig in Package Manager Console.

Also you can create NuGet package and put it to your local NuGet hive. To do this please run NuGet.bat, newly created package will be put to NuGet subfolder.


To enable NConfig in your code, you need only one code line in your application startup section:

NConfigurator.UsingFiles("Config\\Custom.config", "Config\\Connections.config").SetAsSystemDefault();

As result configurations from files {HostName}.Custom.config and {HostName}.Connections.config in Config subfolder will be merged and used in ConfigurationManager instead of default configuration.

Where {HostName} is the current machine name.

In case {HostName}.Custom.config do not exist, Custom.config file will be used. Moreover if Custom.config is missing too, App.config (or Web.config) will be used.

Host Alias and Environment Variable
You can create a custmom alias for a host by setting the HostName and Alias in a HostMap.config. It will then use the {AliasName}.Custom.Config instead of the HostName. See the examples for details.
It's also possible to supply an alias name by setting the environment variable NCONFIG_ALIAS for the running process. This is useful for cloud hosting scenario's where you don't know the hostname in advance.
For Microsoft Azure Websites you can set the NCONFIG_ALIAS as an App Setting through the Azure portal and it will be available as environment variable for NConfig.

You should set Copy To Output Directory = Copy Always for all your custom configuration files, otherwise they will not be copied to Bin folder and NConfig will not find them.


If you are using your custom configuration sections [ (HowTo)], the default "merger" utilizes the first section it finds in the hierachy, discarding settings defined in more general ones. However, you can switch to your own merger type for each section seperately. You even can write your own mergers yourself!

  • AppSettingsMerger Used for the section utilizing only (you cannot remove a setting in higher config files) within all config files.

  • ConectionStringsMerger Used for the section utilizing only (you cannot remove a setting in higher config files) within all config files.

  • DeepMerger Goes down the hierachy and tries to merge attributes also within properties. Merges collections (which need to implmenent IMergeableConfigurationCollection) via their key utilizing also and .

  • DefaultMerger Uses the first occurance of the whole section in hierachy discarding anything in other config files.

  • PropertyLevelMerger Uses the first occurance of any property in hierachy; does not merge sub-properties or attributes.

You can set the merger via NConfigurator.RegisterSectionMerger(new DeepMerger<TestConfigSection>());

Sample code from Samples\ConsoleTest:

	// Setup NConfigurator to use Custom.config file from Config subfolder.

	var testSection = NConfigurator.Default.GetSection<TestConfigSection>();
	var configManagerTestSection = ConfigurationManager.GetSection("TestConfigSection") as TestConfigSection;
	var namedTestSection = NConfigurator.UsingFile(@"Config\Custom.config").GetSection<TestConfigSection>("NamedSection");

	Console.WriteLine("NConfig Default : " + testSection.TestValue);
	Console.WriteLine("ConfigurationManager : " + configManagerTestSection.TestValue);
	Console.WriteLine("NConfig named section : " + namedTestSection.TestValue);

	Console.WriteLine("Merged APP Settings : ");
	foreach(var key in ConfigurationManager.AppSettings.AllKeys)
		Console.WriteLine(key + " : " +  ConfigurationManager.AppSettings[key]);

For more complex examples please refer to Samples subfolder.



In most cases this very popular logging library uses direct access to App.config(Web.config) XML, ignoring ConfigurationManager and therefore ignoring NConfig.

So, how can I configure it?
There are several ways:

First: If you just need to split log4net configuration from App.config.

Use log4net.Config setting in appSettings:

            <add key="log4net.Config" value="Config\separate-log4net.config"/>

Or use [assembly: log4net.Config.XmlConfigurator(ConfigFile = @"Config\separate-log4net.config")] attribute.
Or specify configuration file programmatically

        var fullPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, @"\Config\separate-log4net.config");
        log4net.Config.XmlConfigurator.Configure(new FileInfo(fullPath));

More details [here] (

Second: If you need machine/host dependent log4net configurations.

One of the issue there is that usually log4net initialized earlier than NConfig, because of static field initialization.
private static log4net.ILog log = log4net.LogManager.GetLogger(...);

One way is to use log4net.Config setting with current config file path in your custom configuration file,
and delay logger setup till NConfig initialized.

File Config\Custom.config

      <?xml version="1.0"?>
            <section name="log4net" type="System.Configuration.IgnoreSectionHandler" />

            <!-- This will override any previous log4net.Config settings in app.config and 
                 forces log4net to use this file as configuration. -->
            <add key="log4net.Config" value="Config\Custom.config"/>
            <!-- log4net configuration here -->

Program code:

   private static log4net.ILog log;

   static void Main() {
	// Setup NConfigurator to use Custom.config file from Config subfolder.
	//Delayed log setup, this will configure log4net using current appSettings from Custom.config.
	log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

Another way is to use explicit log4net.Config.XmlConfigurator.Configure(); call after NConfig initialization and declare log4net section as Log4NetConfigurationSectionHandler. This will allow us not to specify any additional configuration file paths in appSettings and will provide smooth NConfig experience.

File Config\Custom.config

      <?xml version="1.0"?>
            <!-- NOTE that we use Log4NetConfigurationSectionHandler to make log4net use ConfigurationManager -->
            <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
            <!-- log4net configuration here -->

Program code:

   private static log4net.ILog log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);

   static void Main() {
	// Setup NConfigurator to use Custom.config file from Config subfolder.
	// Configure log4net using host-based Custom.config configuration file.

Feel free to contact me if you have any other questions related to NConfig integrations.


You can review how NConfig setup by calling NConfigurator.Default.DumpDiagnostics();

The output will be in a form of string that allows you to review what configuration files NConfig is looking for and what files it used to construct the final configuration.

NConfig Diagnostics 
Host name: Workstation
Host alias: Tests
Web Environment: False
Configuration files: 
missing file: 'Tests.NotExisting.config' location: 'C:\NConfig\NConfig.Tests\bin\Debug\Tests.NotExisting.config' 
missing file: 'NotExisting.config' location: 'C:\NConfig\NConfig.Tests\bin\Debug\NotExisting.config' 
exists file: 'Configs\Tests.Aliased.config' location: 'C:\NConfig\NConfig.Tests\bin\Debug\Configs\Tests.Aliased.config' 
exists file: 'Configs\Aliased.config' location: 'C:\NConfig\NConfig.Tests\bin\Debug\Configs\Aliased.config' 


Currently NConfig was tested against ASP.Net, ASP.Net MVC, WinServices, WinForms/WPF, Console apps. Other environments are supposed to be supported too, but I haven't tested them yet.

If you do everything as described before, but no custom configuration applied, please check that settings
Copy To Output Directory = Copy Always
for all your configuration files.

If you encounter any issues please do not hesitate to contact me directly or by raising issue on GitHub.

Windows Activation Service (WAS)

The above global.asax does not work for non-HTTP protocols such as net.tcp and net.pipe that is supported by the Windows Activation Service (WAS) on Windows Vista. There is no protocol-agnostic counterpart for HttpApplication in this case.

Fortunately, ASP.NET provides a simple hook that works in a protocol agnostic way. The hook is based on the following AppInitialize method: public static void AppInitialize(); This method can be put in any type that is defined in a C# file in the application’s \App_Code directory. When the AppDomain is started, ASP.NET checks whether there is a type that has such as method (exact name and signature) and invokes it. Note that the AppInitialize method can be only defined once and it has to be in a code file instead of a pre-compiled assembly. More details [here] (


Section in config is ignored / Config file is ignored

There are several reasons, why a config file or section seemingly is "ignored".

  • Is the section handler defined at the top of the config file? <configSections><section name="testConfigSection" type="Custom.Config.TestConfigSection, TestConfig" /></configSections>

  • Did you set up the merger correctly? NConfigurator.RegisterSectionMerger(new DeepMerger<TestConfigSection>());


I would like to thank my colleagues for helping me testing and fixing this tool. Also thanks to TLK for his help in this file creation. Also I would like to thank the guys at 31337 chat for their support.

The DeepMerger is a contribution by World Direct eBusiness Software GmbH.