Enumerate and Host Control Panel Applets using C#.

using System;
using System.Drawing;
using System.Collections;
using System.Runtime.InteropServices;

namespace AppletEngine
{
	public enum BOOL
	{
		FALSE = 0,
		TRUE  = 1
	}	

	/// <summary>
	/// The AppletLibrary class exposes methods for loading and describing the individual Applets found in a Windows Control Panel library (*.cpl)
	/// </summary>
	public class AppletLibrary : DisposableObject
	{
		private IntPtr _library;
		private IntPtr _appletProc;
		private IntPtr _hWndCpl;
		private string _path;
		private ArrayList _applets;

		#region P/Invoke

		[DllImport("Kernel32")]
		public static extern IntPtr LoadLibrary(string path);

		[DllImport("Kernel32")]
		public static extern bool FreeLibrary(IntPtr hModule);

		[DllImport("Kernel32")]
		public static extern IntPtr GetProcAddress(IntPtr hModule, string procName);
		
		[DllImport("AppletProxy")]
		public static extern int ForwardCallToApplet(IntPtr appletProc, IntPtr hWndCpl, AppletMessages message, IntPtr lParam1, IntPtr lParam2);

		#endregion

		public override void Dispose(bool disposing)
		{
			base.Dispose (disposing);

			if (disposing)
			{

			}

			if (!base.IsNullPtr(_library))
			{
				/// as the control panel closes it sends the CPL_CLOSE message to each applet
				foreach(Applet applet in _applets)
					applet.Close();

				this.CPlApplet(AppletMessages.Exit);
				
				foreach(Applet applet in _applets)
					applet.Dispose(disposing);

				if (!FreeLibrary(_library))
				{
					System.Diagnostics.Trace.WriteLine("Failed to free the library '" + _path + "'");
				}

				_library = IntPtr.Zero;
				_appletProc = IntPtr.Zero;
			}
		}

		/// <summary>
		/// Initializes a new instance of the AppletLibrary class
		/// </summary>
		/// <param name="path"></param>
		/// <param name="hWndCpl"></param>
		public AppletLibrary(string path, IntPtr hWndCpl)
		{
			_path = path;
			_hWndCpl = hWndCpl;
			_applets = new ArrayList();

			if (!System.IO.File.Exists(path))
				throw new System.IO.FileNotFoundException("No applet could be found in the specified path.", path);

			_library = LoadLibrary(path);
			if (base.IsNullPtr(_library))
				throw new Exception("Failed to load the library '" + _path + "'");
			
			_appletProc = GetProcAddress(_library, "CPlApplet");
			if (base.IsNullPtr(_appletProc))
				throw new Exception("Failed to load CPlApplet proc for the library '" + _path + "'");	

			
			this.Initialize();
		}
        
		public IntPtr LibraryHandle
		{
			get
			{
				return _library;
			}
		}

		public string Path
		{
			get
			{
				return _path;
			}
		}

		public ArrayList Applets
		{
			get
			{
				return _applets;
			}
		}

		public int CPlApplet(AppletMessages message, IntPtr lParam1, IntPtr lParam2)
		{
			return ForwardCallToApplet(_appletProc, _hWndCpl, message, lParam1, lParam2);
		}

		public int CPlApplet(AppletMessages message)
		{
			return ForwardCallToApplet(_appletProc, _hWndCpl, message, IntPtr.Zero, IntPtr.Zero);
		}

		public void Initialize()
		{
			if (this.CPlApplet(AppletMessages.Initialize, IntPtr.Zero, IntPtr.Zero) == (int)BOOL.TRUE)
			{
				int count = this.CPlApplet(AppletMessages.GetCount, IntPtr.Zero, IntPtr.Zero);
			
		//				System.Diagnostics.Trace.WriteLine(string.Format("{0} applets found in '{1}'", count, _path));				
						
				for(int i = 0; i < count; i++)
				{
					Applet applet = new Applet(this, i);
					System.Diagnostics.Trace.WriteLine(applet.ToString());
					_applets.Add(applet);
				}			
			}
		}		
	}
}