Win32PowerManagementEvent.cs

using System;
using System.Management;

public class Program
{
    public static void Main(string[] args)
    {
        using (var watcher = new Win32PowerManagementEventWatcher())
        {
            watcher.Start();
            watcher.OnSuspend += OnSystemEvent;
            watcher.OnResume += OnSystemEvent;
            Console.ReadKey();
        }   
    }
    
    private void OnSystemEvent(object sender, Win32PowerManagementEventWatcherEventArgs e)
    {
        Console.WriteLine("Event: {0}", e.EventType);
    }
}

public enum PowerModeEventType : ushort
{
    EnteringSuspend = 4,
    ResumeFromSuspend = 7,
    PowerStatusChanged = 10,
    OemEvent = 11,
    ResumeAutomatic = 18
}

public delegate void Win32PowerManagementEventWatcherEventHandler(object sender, Win32PowerManagementEventWatcherEventArgs e);

public sealed class Win32PowerManagementEventWatcherEventArgs : EventArgs
{
    private readonly DateTime _createdAtUtc;
    private readonly PowerModeEventType _eventType;

    public Win32PowerManagementEventWatcherEventArgs(PowerModeEventType eventType, DateTime createdAtUtc)
    {
        _eventType = eventType;
        _createdAtUtc = createdAtUtc;
    }

    public DateTime CreatedAtUtc
    {
        get
        {
            return _createdAtUtc;
        }
    }

    public PowerModeEventType EventType
    {
        get
        {
            return _eventType;
        }
    }
}

public sealed class Win32PowerManagementEventWatcher : IDisposable
{
    private static readonly TimeSpan MinDelayBetween2Resumes = TimeSpan.FromMinutes(1);
    private readonly ManagementEventWatcher _watcher;
    private bool _started;
    private DateTime _lastResume;

    public event Win32PowerManagementEventWatcherEventHandler OnSuspend;

    public event Win32PowerManagementEventWatcherEventHandler OnResume;

    public event Win32PowerManagementEventWatcherEventHandler OnAnyEvent;

    public Win32PowerManagementEventWatcher()
    {
        WqlEventQuery query = new WqlEventQuery("Win32_PowerManagementEvent");
        _watcher = new ManagementEventWatcher(query);
        _watcher.EventArrived += OnSystemEventsPowerModeChanged;
    }

    public void Start()
    {
        if (_started)
            return;
        _watcher.Start();
        _started = true;
    }

    public void Stop()
    {
        if (!_started)
            return;
        _started = false;
        _watcher.Stop();
    }

        private void OnSystemEventsPowerModeChanged(object sender, EventArrivedEventArgs e)
        {
            // RECOMMENDED: wrapped in a try catch with your logger...
            
            var eventType = (PowerModeEventType)(ushort)e.NewEvent.Properties["EventType"].Value;
            var createdAt = (long)(ulong)e.NewEvent.Properties["TIME_CREATED"].Value;
            var date = DateTime.FromFileTimeUtc(createdAt);
            var arg = new Win32PowerManagementEventWatcherEventArgs(eventType, date);
            OnAnyEvent?.Invoke(this, arg);
            switch (eventType)
            {
                case PowerModeEventType.EnteringSuspend:
                    OnSuspend?.Invoke(this, arg);
                    break;
                case PowerModeEventType.ResumeFromSuspend:
                case PowerModeEventType.ResumeAutomatic:
                    if (date.Subtract(_lastResume) > MinDelayBetween2Resumes)
                    {
                        _lastResume = date;
                        OnResume?.Invoke(this, arg);
                    }
                    break;
                case PowerModeEventType.PowerStatusChanged:
                case PowerModeEventType.OemEvent:
                default:
                    break;
            }
        }

        public void Dispose()
        {
            if (_started)
                Stop();
            _watcher.EventArrived -= OnSystemEventsPowerModeChanged;
            _watcher.Dispose();
        }
    }