Custom App Config Sections

app.config

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <configSections>
    <section name="excludeKeywords" type="YourNameSpace.SectionHandler, YourNamespace" />
  </configSections>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5"/>
  </startup>

  <appSettings>
    <add key="Test" value="Test value!"/>
  </appSettings>

  <!--<includeRegex>
    <regex pattern=""/>
  </includeRegex>-->
  
  <!--Objects can be stored & deserialized in the section handler-->

  <yourSectionName>
    <item value="4097821023436939"/>
    <item value="4010864067044940"/>
  </yourSectionName>
</configuration>

SectionHandler.cs

using System.Collections.Generic;
using System.Configuration;
using System.Xml;

public class ExcludeKeywordSection : IConfigurationSectionHandler
{
    public object Create(object parent, object configContext, XmlNode section)
    {
        List<string> myConfigObject = new List<string>();

        foreach (XmlNode childNode in section.ChildNodes)
        {
            foreach (XmlAttribute attrib in childNode.Attributes)
            {
                myConfigObject.Add(attrib.Value);
            }
        }
        return myConfigObject;
    }
}

Settings.cs

#region Properties

#region - App Config Properties

public static List<string> ExampleList
{
    get
    {
        try
        {
            List<string> list = (List<string>)ConfigurationManager.GetSection("yourSectionName");

            return list;
        }
        catch (Exception)
        {
            return null;
        }
    }
}

#endregion - App Config Properties

#endregion - Properties