SystemEvents.SessionEnding Event

Definition

Namespace:

Microsoft.Win32

Assembly:

Microsoft.Win32.SystemEvents.dll

Source:

SystemEvents.cs

Occurs when the user is trying to log off or shut down the system.

C#

public static event Microsoft.Win32.SessionEndingEventHandler? SessionEnding;

Event Type

SessionEndingEventHandler

Exceptions

InvalidOperationException

System event notifications are not supported under the current context. Server processes, for example, might not support global system event notifications.

ExternalException

The attempt to create a system events window thread did not succeed.

Remarks

This is a cancelable event. Setting the Cancel property to true will request that the session continues to run. It provides no guarantee that the session will not end.

If you are using SessionEnding in a Windows form to detect a system logoff or reboot, there is no deterministic way to decide whether the Closing event will fire before this event.

If you want to perform some special tasks before Closing is fired, you need to ensure that SessionEnding fires before Closing. To do this, you need to trap the WM_QUERYENDSESSION in the form by overriding the WndProc function. This example demonstrates how to do this.

C#

private static int WM_QUERYENDSESSION = 0x11;  
private static bool systemShutdown = false;  
protected override void WndProc(ref System.Windows.Forms.Message m)  
{  
    if (m.Msg==WM_QUERYENDSESSION)  
    {  
        MessageBox.Show("queryendsession: this is a logoff, shutdown, or reboot");  
        systemShutdown = true;  
    }  

    // If this is WM_QUERYENDSESSION, the closing event should be  
    // raised in the base WndProc.  
    base.WndProc(ref m);  

} //WndProc   

private void Form1_Closing(  
    System.Object sender,   
    System.ComponentModel.CancelEventArgs e)  
{  
    if (systemShutdown)  
        // Reset the variable because the user might cancel the   
        // shutdown.  
    {  
        systemShutdown = false;  
        if (DialogResult.Yes==MessageBox.Show("My application",   
            "Do you want to save your work before logging off?",   
            MessageBoxButtons.YesNo))  
        {  
            e.Cancel = true;  
        }  
        else  
        {  
            e.Cancel = false;  
        }  
    }  
}  

Important

Console applications do not raise the SessionEnding event.

Note

This event is only raised if the message pump is running. In a Windows service, unless a hidden form is used or the message pump has been started manually, this event will not be raised. For a code example that shows how to handle system events by using a hidden form in a Windows service, see the SystemEvents class.

Caution

Because this is a static event, you must detach your event handlers when your application is disposed, or memory leaks will result.

Applies to

See also

• SessionEndingEventArgs
• SessionEndingEventHandler
• SessionEndReasons