Handling System Shutdown in a WindowsForms App

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Guest

Hi. I have an application that runs as a Tray Icon app with no visible window
(most of the time) and right now, the system will not shut down while that
app is running. I think I need to handle "SystemEvents.SessionEnded" or
something to properly deal with that but I don't understand how, inside the
code for my Main Form for the application, I set up a handler for the event
and then what I actually DO with the event once it comes (though I assume I
just do whatever I would normally do to exit my application grcefully).

Can someone help me with a sample?

Alex
 
Alex,

Try to handle SessionEnding event first and make sure you don't cancel the
request.

Read carefully MSDN regarding this event because they have some important
remarks there.
 
Forgive my ignorance about this but I'm even a little confused about how I
create a function in my Main Form class and make it handle this event. Can
you give me a small snippet of code or point me somewhere?

Alex

Stoitcho Goutsev (100) said:
Alex,

Try to handle SessionEnding event first and make sure you don't cancel the
request.

Read carefully MSDN regarding this event because they have some important
remarks there.


--
HTH
Stoitcho Goutsev (100) [C# MVP]


Alex Maghen said:
Hi. I have an application that runs as a Tray Icon app with no visible
window
(most of the time) and right now, the system will not shut down while that
app is running. I think I need to handle "SystemEvents.SessionEnded" or
something to properly deal with that but I don't understand how, inside
the
code for my Main Form for the application, I set up a handler for the
event
and then what I actually DO with the event once it comes (though I assume
I
just do whatever I would normally do to exit my application grcefully).

Can someone help me with a sample?

Alex
Click to expand...
Click to expand...
 
More information...

For testing purposes, I've tried creating a simple WindowsForms app in VS
2005 and the copying and pasting the sample code from
"SystemEvents.SessionEnding Event" in the help into the Form1 class. That
sample code is:

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(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;
}
}
}

When I try to run the app, I get an error about the "base.WndProc(m);" line
above. What am I doing wrong?

Alex





Alex Maghen said:
Forgive my ignorance about this but I'm even a little confused about how I
create a function in my Main Form class and make it handle this event. Can
you give me a small snippet of code or point me somewhere?

Alex

Stoitcho Goutsev (100) said:
Alex,

Try to handle SessionEnding event first and make sure you don't cancel the
request.

Read carefully MSDN regarding this event because they have some important
remarks there.


--
HTH
Stoitcho Goutsev (100) [C# MVP]


Alex Maghen said:
Hi. I have an application that runs as a Tray Icon app with no visible
window
(most of the time) and right now, the system will not shut down while that
app is running. I think I need to handle "SystemEvents.SessionEnded" or
something to properly deal with that but I don't understand how, inside
the
code for my Main Form for the application, I set up a handler for the
event
and then what I actually DO with the event once it comes (though I assume
I
just do whatever I would normally do to exit my application grcefully).

Can someone help me with a sample?

Alex
Click to expand...
Click to expand...
Click to expand...
 
Alex,

The error is that you need to use *ref* infront of the *m* parameter when
calling the base methods.

This is the code that you can use to test the sample. I changed also the
event handler to override OnClosing methods, which is the preferable way of
handling events in a case of inheritance.

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


protected override void OnClosing(CancelEventArgs e)
{

base.OnClosing(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;
}
}
}


--

Stoitcho Goutsev (100) [C# MVP]


Alex Maghen said:
More information...

For testing purposes, I've tried creating a simple WindowsForms app in VS
2005 and the copying and pasting the sample code from
"SystemEvents.SessionEnding Event" in the help into the Form1 class. That
sample code is:

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(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;
}
}
}

When I try to run the app, I get an error about the "base.WndProc(m);"
line
above. What am I doing wrong?

Alex





Alex Maghen said:
Forgive my ignorance about this but I'm even a little confused about how
I
create a function in my Main Form class and make it handle this event.
Can
you give me a small snippet of code or point me somewhere?

Alex

Stoitcho Goutsev (100) said:
Alex,

Try to handle SessionEnding event first and make sure you don't cancel
the
request.

Read carefully MSDN regarding this event because they have some
important
remarks there.


--
HTH
Stoitcho Goutsev (100) [C# MVP]


Hi. I have an application that runs as a Tray Icon app with no
visible
window
(most of the time) and right now, the system will not shut down while
that
app is running. I think I need to handle "SystemEvents.SessionEnded"
or
something to properly deal with that but I don't understand how,
inside
the
code for my Main Form for the application, I set up a handler for the
event
and then what I actually DO with the event once it comes (though I
assume
I
just do whatever I would normally do to exit my application
grcefully).

Can someone help me with a sample?

Alex
Click to expand...
Click to expand...
Click to expand...
 
Hi Alex,

Yes, it seems that the MSDN sample missed "ref " in base.WndProc(m)
statement.
The correct code is:
base.WndProc(ref m), which has been pointed out by "Stoitcho Goutsev
\(100\) [C# MVP]".

Thanks

Best regards,
Jeffrey Tan
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.
 
Hi Alex,

Does our replies make sense to you? Is your problem resolved? Please feel
free to tell me, thanks

Best regards,
Jeffrey Tan
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.
 
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