C# : Custom configuration section

February 12, 2011 by Christoff Truter C#  

Generally when we develop applications using .NET, we use our app/web.config as a place where we expose certain settings to our application(s) (its even possible to encrypt it for those who dare or feel the higher calling to use it to store sensitive information).

Your config file will likely look something like this:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="1" value="a" />
    <add key="2" value="b" />
    <add key="3" value="c" />
  </appSettings>
</configuration>

Next we'll wack a reference to the system.configuration assembly into our application, which will allow us to access our settings via the ConfigurationManager - like seen in the following image.



Now we can always simply use the general appSettings section to store some rudimentary settings, but what if we wish to create a separate appSettings section specific to our company for example?

In the following snippet we do exactly that, we add a new section called "Company.appSettings", using one of the default section handlers, observe:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="Company.appSettings" type="System.Configuration.NameValueFileSectionHandler" />
  </configSections>
  <Company.appSettings>
    <add key="1" value="a" />
    <add key="2" value="b" />
    <add key="3" value="c" />
  </Company.appSettings>
  <appSettings />
</configuration>

Programmatically we'll access the newly added section like this:

NameValueCollection settings = ConfigurationManager.GetSection("Company.appSettings") as NameValueCollection;
if (settings != null)
{
	foreach (string key in settings)
	{
		Console.WriteLine("{0} : {1}", key, settings[key]);
	}
}

An alternative to using notation like Company.appSettings is that you can instead separate your custom sections using the sectionGroup node like so:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <sectionGroup name="Company">
      <section name="appSettings" type="System.Configuration.NameValueFileSectionHandler" />
    </sectionGroup>
  </configSections>
  <Company>
    <appSettings>
      <add key="1" value="a" />
      <add key="2" value="b" />
      <add key="3" value="c" />
    </appSettings>
  </Company>
  <appSettings />
</configuration>

Accessing the settings from code will look something like this:

NameValueCollection settings = ConfigurationManager.GetSection("Company/appSettings") as NameValueCollection;

This is obviously not the limit to the customization possibilities - you might have seen/used the following settings in your config file when setting up .NET for sending mail:

<system.net>
  <mailSettings>
    <smtp>
      <network host="smtp.somehost.net" />
    </smtp>
  </mailSettings>
</system.net>

It is quite easy to create our own custom section similar to what we see in the preceding snippet.

The following snippet will give you a quick idea on how to create your own custom section, note inherited classes ConfigurationSection and ConfigurationElement.

using System;
using System.Configuration;

namespace Sections
{
    public class XSection : ConfigurationSection
    {
        [ConfigurationProperty("x", DefaultValue = false, IsRequired = false)]
        public Boolean X
        {
            get
            {
                return (Boolean)this["x"];
            }
            set
            {
                this["x"] = value;
            }
        }

        [ConfigurationProperty("y")]
        public YElement Y
        {
            get
            {
                return (YElement)this["y"];
            }
            set
            {
                this["y"] = value;
            }
        }
    }

    public class YElement : ConfigurationElement
    {
        [ConfigurationProperty("y1", DefaultValue = "value", IsRequired = false)]
        public String Y1
        {
            get
            {
                return (String)this["y1"];
            }
            set
            {
                this["y1"] = value;
            }
        }

        [ConfigurationProperty("y2", IsRequired = true)]
        public Int32 Y2
        {
            get
            {
                return (Int32)this["y2"];
            }
            set
            {
                this["y2"] = value;
            }
        }
    }
}

The custom section will look something like this in your config file:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <configSections>
    <section name="XSection" type="Sections.XSection, ConsoleApplication1"  allowLocation="true"
        allowDefinition="Everywhere" />
  </configSections>
  <XSection x="true">
    <y y1="test1" y2="10" />
  </XSection>
</configuration>

In order to access the custom node from code, you need to do the following:

Sections.XSection xsection = ConfigurationManager.GetSection("XSection") as Sections.XSection;
if (xsection != null)
{
    Console.WriteLine(xsection.X);
    Console.WriteLine(xsection.Y.Y1);
    Console.WriteLine(xsection.Y.Y2);
}

There is a lot of other options also available, like the configurationcollection attribute - which allows us to add collections as settings to our config files - be sure to read the additional reading at the bottom of the page.

Additional Reading:
http://msdn.microsoft.com/en-us/library/2tw134k3.aspx
http://msdn.microsoft.com/en-us/library/system.configuration.configurationcollectionattribute.aspx