SystemEvents.SessionEnding Event
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Occurs when the user is trying to log off or shut down the system.
public:
static event Microsoft::Win32::SessionEndingEventHandler ^ SessionEnding;public static event Microsoft.Win32.SessionEndingEventHandler? SessionEnding;public static event Microsoft.Win32.SessionEndingEventHandler SessionEnding;member this.SessionEnding : Microsoft.Win32.SessionEndingEventHandler Public Shared Custom Event SessionEnding As SessionEndingEventHandler Event Type
Exceptions
System event notifications are not supported under the current context. Server processes, for example, might not support global system event notifications.
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.
Private Shared WM_QUERYENDSESSION As Integer = &H11
Private Shared systemShutdown As Boolean = False
Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
If m.Msg = WM_QUERYENDSESSION Then
MessageBox.Show("queryendsession: this is a logoff, shutdown, or reboot")
systemShutdown = True
End If
' If this is WM_QUERYENDSESSION, the closing event should be raised in the base WndProc.
MyBase.WndProc(m)
End Sub 'WndProc
Private Sub Form1_Closing(ByVal sender As System.Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
If (systemShutdown) Then
' Reset the variable because the user might cancel the shutdown.
systemShutdown = False
If (System.Windows.Forms.DialogResult.Yes = _
MessageBox.Show("My application", "Do you want to save your work before logging off?", MessageBoxButtons.YesNo)) Then
e.Cancel = True
Else
e.Cancel = False
End If
End If
End Sub
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.
