Every now and then I find myself needing to create a custom configuration section for a .NET application or module that I’m building. It’s not something I do often enough to remember how to do it by heart though so I usually consult Google, only there I often find guides that are either to long and/or verbose or doesn’t quite match how I like to do it. So I end up digging up some of my old code where I’ve created a custom configuration section. While that works it takes more time than it should so I thought I’d help myself by posting a quick little guide here.

Creating a basic Configuration Section

Given the class below…

using System.Configuration;

namespace ConfigurableModule
{
    public class Configuration : ConfigurationSection  
    {
        public static Configuration GetConfiguration()
        {
            Configuration configuration = 
                ConfigurationManager
                .GetSection("myConfigurableModule")
                as Configuration;

            if (configuration != null)
                return configuration;

            return new Configuration();
        }

        [ConfigurationProperty("message", IsRequired = false)]
        public string Message
        {
            get
            {
                return this["message"] as string;
            }
        }
    }
}

…and the following in our applications configuration file (app.config/web.config)…

<configuration>
    <configSections>
        <section name="myConfigurableModule" type="ConfigurableModule.Configuration, ConfigurableModule"/>
    </configSections>
    <myConfigurableModule message="Hello world!" />
    <!-- Optionally other configuration -->
</configuration>

…we can get the Message property from the configuration like this:

string messageFromConfiguration
    = ConfigurableModule.Configuration
        .GetConfiguration().Message ;

Storing the configuration section in a separate file

We can move our configuration section to a separate file using the configSource attribute. To do that in the above example we change it like this:

<configuration>
    <configSections>
        <section name="myConfigurableModule" type="ConfigurableModule.Configuration, ConfigurableModule"/>
    </configSections>
    <myConfigurableModule configSource="myConfigurableModule.config" />
    <!-- Optionally other configuration -->
</configuration>

The file myConfigurableModule.config should then look like this:

<myConfigurableModule 
    message="Hello world from a separate file!" />

Creating ConfigurationElements, ConfigurationElementCollections etc

The above is usually all I need, but if a more extensive configuration is needed, requiring separate elements etc there is a more extensive guide on MSDN.

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