Dapplo.Windows.SystemState 3.6.3

Dapplo.Windows.SystemState

Power management for .NET on Windows: keep the system awake while your application works, put it to sleep or shut it down, wake it up with a timer, and react to suspend / resume. Targets net480 and net10.0-windows.

This package is part of Dapplo.Windows. Full documentation: Power and system state, changes: changelog.

Preventing sleep

PreventSleep keeps the system and the display on, PreventSystemSleep only the system, until the returned SleepBlocker is disposed. It's a power request, not bound to a thread, so it works around await.

Namespace: Dapplo.Windows.SystemState.

// Keep the system and the display on until the blocker is disposed
using (SystemStateApi.PreventSleep("Recording the screen"))
{
    await RecordAsync();
}

// Keep only the system awake, the display may turn off
using (SystemStateApi.PreventSystemSleep("Uploading files"))
{
    await UploadAsync();
}

Sleep, shut down, log off, lock

// Sleep (suspend to RAM), applications get PBT_APMSUSPEND first
bool ok = PowerManagementApi.Sleep();

// Hibernate (suspend to disk)
ok = PowerManagementApi.Hibernate();

// Sleep, and don't let wake timers wake the system
ok = PowerManagementApi.Sleep(disableWakeEvent: true);

Shutdown and Restart enable the shutdown privilege and log a planned shutdown. Without force hung applications are ended after a timeout; force: true closes everything without asking.

// Log off the current user
PowerManagementApi.LogOff();

// Power off; applications which don't respond are terminated after a timeout
if (!PowerManagementApi.Shutdown())
{
    // e.g. 1314 (ERROR_PRIVILEGE_NOT_HELD) when the user may not shut down
    Console.WriteLine($"Shutdown failed: {System.Runtime.InteropServices.Marshal.GetLastWin32Error()}");
}

// Restart
PowerManagementApi.Restart();

// Close all applications without asking them, they can lose data
PowerManagementApi.Shutdown(force: true);

// The same as Win+L. true means the lock was started, the screen might not be locked yet.
bool started = PowerManagementApi.LockWorkStation();

Wake timers

WaitableTimer can wake the PC from sleep or hibernation (the power option "Allow wake timers" must be enabled; no privilege is needed).

using var timer = new WaitableTimer();

// Wake the PC from sleep or hibernation in 2 hours.
// No privilege is needed, but the "Allow wake timers" power setting must be enabled.
if (!timer.SetOnce(TimeSpan.FromHours(2), wakeSystem: true))
{
    Console.WriteLine("Could not set the timer");
    return;
}

// After the wake-up Windows broadcasts PBT_APMRESUMEAUTOMATIC, and the wait returns
timer.Wait(TimeSpan.FromHours(3));

using var timer = new WaitableTimer();

// First after 1 second, then every 5000 milliseconds
timer.SetPeriodic(initialDelay: TimeSpan.FromSeconds(1), period: 5000);

for (var i = 0; i < 5; i++)
{
    timer.Wait(TimeSpan.FromSeconds(10));
    Console.WriteLine($"Tick {i + 1}");
}

timer.Cancel();

Power events

PowerBroadcastListener reports WM_POWERBROADCAST (through the SharedMessageWindow of Dapplo.Windows.Messages). Events arrive on a background thread while Windows waits: save state synchronously when suspending.

Namespaces: System.Reactive.Linq, Dapplo.Windows.SystemState.Enums.

// Called on the SharedMessageWindow thread while Windows waits (about 2 seconds): save your state synchronously
var suspendSubscription = PowerBroadcastListener.Suspending
    .Subscribe(_ => SaveState());

// The user is back (opened the lid, pressed a key); this is the moment to reconnect
var resumeSubscription = PowerBroadcastListener.ResumedFromSuspend
    .Subscribe(_ => Reconnect());

// Stop listening
suspendSubscription.Dispose();
resumeSubscription.Dispose();

var subscription = PowerBroadcastListener.PowerEvents
    .Subscribe(powerEvent =>
    {
        switch (powerEvent)
        {
            case PowerBroadcastEvent.PBT_APMSUSPEND:
                Console.WriteLine("Suspending");
                break;
            case PowerBroadcastEvent.PBT_APMRESUMEAUTOMATIC:
                Console.WriteLine("Resumed");
                break;
            case PowerBroadcastEvent.PBT_APMRESUMESUSPEND:
                Console.WriteLine("Resumed, the user is present");
                break;
            case PowerBroadcastEvent.PBT_APMPOWERSTATUSCHANGE:
                Console.WriteLine("Power source or battery level changed");
                break;
        }
    });