Asynchronous Registry Notification Using Strongly-typed WMI Classes in .NET

using System;
using System.Collections.Generic;
using System.Management;
using System.Text;

using Microsoft.Win32;

namespace RegistryMonitor
{
	public abstract class RegistryChangeBase : ManagementEventWatcher
	{
		#region Static Fields

		static List<string> validHiveList = new List<string>();
		static string Format = "{{0}} = '{0}' OR ";

		#endregion Static Fields

		#region Constructors

		static RegistryChangeBase()
		{
			string[] validHive = new string[] { "HKEY_LOCAL_MACHINE", "HKEY_USERS", "HKEY_CURRENT_CONFIG" };
			validHiveList.AddRange(validHive);
		}

		protected RegistryChangeBase(string Hive, List<string> KeyPathCollection)
		{
			ValidateHive(Hive);

            ValidateKeyPathList(KeyPathCollection);

			this.Query.QueryLanguage = "WQL";

            this.Scope.Path.NamespacePath = @"root\default";
		}

        protected RegistryChangeBase(string Hive, string KeyPath)
            : this(Hive, new List<string>(new string[] { KeyPath }))
        { }

		#endregion Constructors

		#region Private Methods

		private void ValidateHive(string Hive)
		{
			if (!validHiveList.Contains(Hive.ToUpper()))
			{
			    if (string.IsNullOrEmpty(Hive))
			        throw new ArgumentNullException("Hive", "Hive cannot be null");
			    else
			        throw new ArgumentException("Hive", "Incorrect value");
			}
		}

		private void ValidateKeyPathList(List<string> KeyPathCollection)
		{
            if (KeyPathCollection.Count==0)
            {
                throw new ArgumentNullException("Keypath", "KeyPath cannot be null");
            }

            foreach (string item in KeyPathCollection)
            {
                if (string.IsNullOrEmpty(item))
                {
                    throw new ArgumentNullException("Keypath", "KeyPath cannot be null");
                }
            }
		}

		#endregion Private Methods

		#region Protected Methods

		protected static string BuildOrString(List<string> Values)
		{
			StringBuilder builder = new StringBuilder();
			foreach (string item in Values)
			{
			    builder.Append(string.Format(Format, item));
			}
			builder.Remove(builder.Length - 4, 4);
			return builder.ToString();
		}

		#endregion Protected Methods
	}
}