Event to detect System wake up from sleep in C#

Question

I need to detect the system power state mode. To be precise, I need an event which fires up when windows 7 wakes up from sleep. I am already using:

SystemEvents.PowerModeChanged += SystemEvents_PowerModeChanged;

But the problem with this event is that it is raised up four times: possibly when computer goes into sleep mode and after computer wakes up. I want an event which is raised at computer wake up only. Is there any event for this?

`PowerModeEventArgs` has a property called `Mode` that you can use to say what state its returning to — Sayse, Aug 13 '13 at 10:05
possible duplicate of [How can I know when Windows is going into/out of sleep or Hibernate mode?](http://stackoverflow.com/questions/228288/how-can-i-know-when-windows-is-going-into-out-of-sleep-or-hibernate-mode) — Ian R. O'Brien, Aug 05 '14 at 13:24

Marcus · Accepted Answer · 2013-08-13T10:24:19.883

61

SystemEvents.PowerModeChanged += OnPowerChange;

private void OnPowerChange(object s, PowerModeChangedEventArgs e) 
{
    switch ( e.Mode ) 
    {
        case PowerModes.Resume: 
        break;
        case PowerModes.Suspend:
        break;
    }
}

You should probably read this: http://msdn.microsoft.com/en-us/library/microsoft.win32.systemevents.powermodechanged.aspx

edited Aug 13 '13 at 10:24

answered Aug 13 '13 at 10:14

Marcus

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7

Don't forget to unsubscribe the event: `SystemEvents.PowerModeChanged -= OnPowerChange;` – ramaral Nov 06 '18 at 22:36
2

Doesn't seem to work with the "new" Connected/Modern Standby modes... Possible substitute in this question: https://stackoverflow.com/questions/20119257/connected-standby-notification-for-a-w8-service/55676206#55676206 – Oded Ben Dov Apr 14 '19 at 14:11
@ramaral at what point the even listener needs to be removed and why exactly? – Adil Malik May 06 '19 at 14:19
2

@AdilMalik Because this is a static event.When an event is subscribed, the class that owns the event maintains a reference to the subscriber. As long as this reference exists the subscriber can not be collected by the garbage collector and a memory leak will occur, . – ramaral May 06 '19 at 17:57
1

@AdilMalik The event should be unsubscribe when no longer needed or just before the subscriber is not need anymore. See [SystemEvents.PowerModeChanged Event](https://learn.microsoft.com/en-us/dotnet/api/microsoft.win32.systemevents.powermodechanged?redirectedfrom=MSDN&view=netframework-4.8) – ramaral May 06 '19 at 18:04

score 10 · Answer 2 · answered Aug 13 '13 at 10:07

You need to inspect the Mode property of the PowerModeChangedEventArgs that is passed to the event.

From MSDN:

Resume The operating system is about to resume from a suspended state.

StatusChange A power mode status notification event has been raised by the operating system. This might indicate a weak or charging battery, a transition between AC power and battery, or another change in the status of the system power supply.

Suspend The operating system is about to be suspended.

Event to detect System wake up from sleep in C#

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