Messages in C # that shield forms are closed

Often can see such a program, point to turn off the button after the program does not close, but minimized to the system tray, like NetEase bubble, MSN and other programs. Implementing this is actually very simple, and capturing the message when the form is closed is OK. The code is as follows:

protected override void WndProc (ref message M)
{
const int wm_syscommand = 0x0112;
const int sc_close = 0xf060;
if (m.msg = = Wm_syscommand && (int) M.wparam = = Sc_close)
{
MessageBox.Show ("User points off button");
Return
}
Base. WndProc (ref m);
}

This passage is in the form code.