Mine

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Text;

namespace xxx.xxx.WorkFlows.SharedActivities.Configuration
{
    public class RegexParserElement : ConfigurationElement
    {
        #region Fields
        private static ConfigurationProperty o_RegexPattern;
        private static ConfigurationProperty o_Groups;

        private static ConfigurationPropertyCollection oc_Properties;
        #endregion

        #region Properties

        #region RegexPattern
        public string RegexPattern
        {
            get
            {
                return (string)this[o_RegexPattern];
            }
            set
            {
                this[o_RegexPattern] = value;
            }
        }
        #endregion

        #region Groups
        public RegexParserGroupElementCollection Groups
        {
            get
            {
                return (RegexParserGroupElementCollection)this[o_Groups];
            }
        }
        #endregion

        #region Properties
        /// <summary>
        /// Override the Properties collection and return our custom one.
        /// </summary>
        protected override ConfigurationPropertyCollection Properties
        {
            get
            {
                return oc_Properties;
            }
        }
        #endregion

        #endregion

        #region Constructor
        static RegexParserElement()
        {
            o_RegexPattern = new ConfigurationProperty("regexPattern", typeof(string), string.Empty, ConfigurationPropertyOptions.IsRequired);
            o_Groups = new ConfigurationProperty("groups", typeof(RegexParserGroupElementCollection), null, ConfigurationPropertyOptions.IsRequired);

            oc_Properties = new ConfigurationPropertyCollection();

            oc_Properties.Add(o_RegexPattern);
            oc_Properties.Add(o_Groups);
        }
        #endregion
    }
}