Tag Archives: IConfigurationSectionHandler

Custom List In app.config File

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I recently had the need to define a custom list in an application. There are many ways to make this happen but I wanted it in the app config file.

After a few searches, I pieced together the following example.

The app.config below has a custom section, AppConfigCollection.CustomDictionary. This section is declared in the configSections and the type attribute has my handler class and assembly name.

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<?xml version="1.0" encoding="utf-8" ?>
<configuration>
 
  <configSections>
    <section name="AppConfigCollection.CustomDictionary" type="AppConfigCollection.CustomDictionary, AppConfigCollection"/>
  </configSections>
 
  <AppConfigCollection.CustomDictionary>
 
    <NFL>
      <AFC>
        <AFC_WEST>
          <Item code="DEN" team="Denver Broncos" />
          <Item code="MCI" team="Kansas City Chiefs" />
          <Item code="SAN" team="San Diego Chargers" />
          <Item code="OAK" team="Oakland Raiders" />
        </AFC_WEST>
      </AFC>
 
      <NFC>
        <NFC_EAST>
          <Item code="DFW" team="Dallas Cowboys" />
          <Item code="PHL" team="Philadelphia Eagles" />
          <Item code="EWR" team="New York Giants" />
          <Item code="IAD" team="Washington Redskins" />
        </NFC_EAST>
      </NFC>
    </NFL>
 
  </AppConfigCollection.CustomDictionary>
 
</configuration>

The handler class CustomDictionary inherits from IConfigurationSectionHandler. This interface has been deprecated but it’s still available and easy to implement and make it work.

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using System;
using System.Collections.Generic;
using System.Configuration;
using System.Linq;
using System.Xml.Linq;
 
namespace AppConfigCollection
{
 
    class Program
    {
        static void Main(string[] args)
        {
            var teamDictionary = (Dictionary<string, string>)ConfigurationManager.GetSection("AppConfigCollection.CustomDictionary");
 
            Console.WriteLine();
            Console.WriteLine("NFL TEAMS");
            foreach (var key in teamDictionary.Keys)
            {
                Console.WriteLine("{0} : {1}", key, teamDictionary[key]);
            }
 
            Console.WriteLine();
            Console.WriteLine("press any key to continue ...");
            Console.ReadLine();
        }
    }
 
    public class CustomDictionary : IConfigurationSectionHandler
    {
        public object Create(object parent, object configContext, System.Xml.XmlNode section)
        {
            var rList = new Dictionary<string, string>();
 
            var doc = XDocument.Parse(section.OuterXml);
            var root = (XElement)doc.FirstNode;
 
            var rootElement = (XElement)root.FirstNode;
            if (rootElement.Name != "NFL")
                throw new ConfigurationErrorsException(
                    "AppConfigCollection.CustomDictionary section only accepts 'NFL' elements.");
 
            try
            {
                foreach (XElement conference in rootElement.Nodes())
                {
                    Console.WriteLine();
                    Console.WriteLine("Conference : {0}", conference.Name);
 
                    foreach (XElement division in conference.Nodes())
                    {
                        Console.WriteLine("  Division : {0}", division.Name);
 
                        var teamList = from div in division.Elements("Item") select div;
                        foreach (var item in teamList)
                        {
                            var code = item.Attribute("code").Value;
                            var team = item.Attribute("team").Value;
 
                            Console.WriteLine("    Team ({0}) : {1}", code, team);
                            rList.Add(code, team);
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                throw new ConfigurationErrorsException(
                    "Error reading element.", ex);
            }
 
            return rList;
        }
    }
 
}

This is the output.
AppConfigCollection

Feel free to download the application solution – experiment and adapt it for your needs.