Tray application allow system to kill my program when logouting or exiting

Question

My program is starting with windows, I have such code to prevent exiting application when user hits exit button:

    protected override void OnClosing(CancelEventArgs e)
    {
        this.ShowInTaskbar = false;
        e.Cancel = true;
        this.Hide();
    }

It is working very well, but when I want to turn off computer, every time I get screen like 'One or more application cannot be exited. Cancel - Exit despite this.

How can I allow windows to normally exit my application, but also prevent user from exiting it when click red exit button?

Answer 1

See How to detect Windows shutdown or logoff.

In the SessionEnded event handler, set a boolean like sessionEnded and in your OnClosing test for that value:

if (!sessionEnded)
{
    e.Cancel = true;
    this.Hide();
}

Answer 2

This helped (thanks to CodeCaster):

    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)
        {
            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)
    {
        this.ShowInTaskbar = false;
        if (!systemShutdown)
        {
            e.Cancel = true;
            this.Hide();
        }
    }