Detect laptop lid closure and opening

Use WM_POWERBROADCAST. Here's a link that can help you: Lid Close Action change notification

Complete working C# code for WPF application that shows how to listen to lid open/close events:

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Interop;

namespace WpfApplication1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        [DllImport(@"User32", SetLastError = true, EntryPoint = "RegisterPowerSettingNotification",
            CallingConvention = CallingConvention.StdCall)]

        private static extern IntPtr RegisterPowerSettingNotification(IntPtr hRecipient, ref Guid PowerSettingGuid,
            Int32 Flags);

        internal struct POWERBROADCAST_SETTING
        {
            public Guid PowerSetting;
            public uint DataLength;
            public byte Data;
        }

        Guid GUID_LIDSWITCH_STATE_CHANGE = new Guid(0xBA3E0F4D, 0xB817, 0x4094, 0xA2, 0xD1, 0xD5, 0x63, 0x79, 0xE6, 0xA0, 0xF3);
        const int DEVICE_NOTIFY_WINDOW_HANDLE = 0x00000000;
        const int WM_POWERBROADCAST = 0x0218;
        const int PBT_POWERSETTINGCHANGE = 0x8013;

        private bool? _previousLidState = null;

        public MainWindow()
        {
            InitializeComponent();
            this.SourceInitialized += MainWindow_SourceInitialized;
        }

        void MainWindow_SourceInitialized(object sender, EventArgs e)
        {
            RegisterForPowerNotifications();
            IntPtr hwnd = new WindowInteropHelper(this).Handle;
            HwndSource.FromHwnd(hwnd).AddHook(new HwndSourceHook(WndProc));
        }

        private void RegisterForPowerNotifications()
        {
            IntPtr handle = new WindowInteropHelper(Application.Current.Windows[0]).Handle;
            IntPtr hLIDSWITCHSTATECHANGE = RegisterPowerSettingNotification(handle,
                 ref GUID_LIDSWITCH_STATE_CHANGE,
                 DEVICE_NOTIFY_WINDOW_HANDLE);
        }

        IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
        {
            switch (msg)
            {
                case WM_POWERBROADCAST:
                    OnPowerBroadcast(wParam, lParam);
                    break;
                default:
                    break;
            }
            return IntPtr.Zero;
        }

        private void OnPowerBroadcast(IntPtr wParam, IntPtr lParam)
        {
            if ((int)wParam == PBT_POWERSETTINGCHANGE)
            {
                POWERBROADCAST_SETTING ps = (POWERBROADCAST_SETTING)Marshal.PtrToStructure(lParam, typeof(POWERBROADCAST_SETTING));
                IntPtr pData = (IntPtr)((int)lParam + Marshal.SizeOf(ps));
                Int32 iData = (Int32)Marshal.PtrToStructure(pData, typeof(Int32));
                if (ps.PowerSetting == GUID_LIDSWITCH_STATE_CHANGE)
                {
                    bool isLidOpen = ps.Data != 0;

                    if (!isLidOpen == _previousLidState)
                    {
                        LidStatusChanged(isLidOpen);
                    }

                    _previousLidState = isLidOpen;
                }
            }
        }

        private void LidStatusChanged(bool isLidOpen)
        {
            if (isLidOpen)
            {
                //Do some action on lid open event
                Debug.WriteLine("{0}: Lid opened!", DateTime.Now);
            }
            else
            {
                //Do some action on lid close event
                Debug.WriteLine("{0}: Lid closed!", DateTime.Now);
            }
        }
    }
}

Keep in mind that most laptops, when the lid closes, it depresses a button. This button is usually just a sleep button. The WMI classes expose the ACPI and you would ideally want to use the PowerManagement Class. Unfortunately, the class does not raise an event when the operating system is set to "do nothing". The only way around this would be to use the DDK (Driver Development Kit) to create a filter that intercepts the IOCTL_GET_SYS_BUTTON_EVENT event. Here are two links to help you get started:

http://blogs.msdn.com/b/doronh/archive/2006/09/08/746834.aspx

and

http://support.microsoft.com/kb/302092