SystemEvents.PowerModeChanged event handler not being called in VSTO & WPF apps

Question

I am developing a VSTO application-level Word AddIn and a WPF application, both need to be notified when the system goes to sleep and subsequently resumes. I have bound my event handlers to the SystemEvents.PowerModeChanged event in each application, but for some reason it still never gets called when the system goes to sleep or resumes. Just to test, I am simply trying to write to the console when the system goes to sleep. I also tried setting breakpoints, but that didn't work either; although I'm not sure if they would've anyway, given that the system is suspending applications. With either attempt, it never prints nor breaks:

VSTO Addin

void ThisAddIn_Startup(object sender, EventArgs e)
{
  SystemEvents.PowerModeChanged += new PowerModeChangedEventHandler(powerModeChanged);
}

public void powerModeChanged(object sender, PowerModeChangedEventArgs args)
{
  Console.WriteLine("Sleeping.....");
}

WPF

internal MyControl()
{
    SystemEvents.PowerModeChanged += new PowerModeChangedEventHandler(powerModeChanged);
}

 public void powerModeChanged(object sender, PowerModeChangedEventArgs args)
 {
     Console.WriteLine("Sleeping!!");
 }

I have tried changing the access level of the event handlers from public to private to internal and vice-versa as well as moving the binding to other parts of the code in each application, but it didn't solve the issue. Any help would be greatly appreciated thank you!

SOLUTION: As per the comments and helpful answer, the event wasn't firing because I was running windows through a VirtualBox VM. Once my coworker ran the code on a native windows machine, it worked.

This is most likely caused, because you dont have an Console in VSTO. Try to write into a File instead of Console to ensure your Event gets fired. — lokusking
@lokusking just tried that and it didn't work, I guess that means my EventHandler isn't being bound to the event correctly? — mattyb
Also, I'm running this on a VirtualBox Windows 10 VM instance, not sure if that could be an issue? — mattyb
Another option is found here. Tbh, i dont know if this handles the Suspension aswell — lokusking
Using Console.WriteLine() in a library that is used in apps that don't have a console is not productive, you can of course never see it. Another classic hangup is that the machine's power mode changed before .NET had an opportunity to call your event handler. You'll get the event twice when the machine is powered up again :) Using it in a VM, just don't bother. — Hans Passant

jsanalytics jsanalytics · Accepted Answer · 2016-09-12T11:16:05

Try this:

XAML:

<Window x:Class="WpfApplication279.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:WpfApplication279"
    mc:Ignorable="d"
    Title="MainWindow" Height="350" Width="525" Loaded="Window_Loaded">
<Grid>
    <ListView x:Name="listView1" Margin="0">
        <ListView.View>
            <GridView>
                <GridViewColumn/>
            </GridView>
        </ListView.View>
    </ListView>

</Grid>

MainWindow:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    private void Window_Loaded(object sender, RoutedEventArgs e)
    {
        SystemEvents.PowerModeChanged += SystemEvents_PowerModeChanged;
    }

    private void SystemEvents_PowerModeChanged(object sender, PowerModeChangedEventArgs e)
    {
        listView1.Items.Add(string.Format("{0} : Power mode changed = {1}", DateTime.Now, e.Mode));
    }
}

In order to trigger the event in a Windows 10 machine, right-click the Start button and then:

Letting the machine go into sleep mode by timeout works the same way. These are my settings:

Same result:

SystemEvents.PowerModeChanged event handler not being called in VSTO & WPF apps

1 Answers