Message Box with timeout using NTMessageBoxSimple

[Bidder]

I have seen several requests for timeout message box functionality.

Just sharing some code used in a recent project.




If timeout happens Rtn.ToString() will be "Cancel"

Also check out the help text article on "NTMessageBoxSimple" if you need help finding the window object

        Thread th = new Thread(() => {
                                
            string Txt = "Message text to display";
            string Cap = "Message box caption";
                        
            NtMsgResult Mb = new NtMsgResult();
            MessageBoxResult Rtn = Mb.Show(Window,Txt,Cap,10000);
            
            Print(Rtn.ToString() );
        
        });
        th.SetApartmentState(ApartmentState.STA);
        th.Start();
        ​

        public class NtMsgResult
        {
            #region Class vars
            private string _caption;
            private System.Threading.Timer _timeoutTimer;
            const int WM_CLOSE = 0x0010;
            [System.Runtime.InteropServices.DllImport("user32.dll", SetLastError = true)]
            static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
            [System.Runtime.InteropServices.DllImport("user32.dll", CharSet = System.Runtime.InteropServices.CharSet.Auto)]
            static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);
            #endregion
            
            public NtMsgResult(){}
            
            public MessageBoxResult Show(Window win, string text, string caption, int timeout)
            {
                return Show(win, text, caption, timeout, MessageBoxButton.YesNo, MessageBoxImage.Question) ;
            }
            
            public MessageBoxResult Show(Window win, string text, string caption, int timeout, MessageBoxButton Btns, MessageBoxImage Img)
            {
                _caption = caption;
                _timeoutTimer = new System.Threading.Timer(OnTimerElapsed,
                    null, timeout, System.Threading.Timeout.Infinite);
                using(_timeoutTimer)
                {
                    MessageBoxResult Rtn = NTMessageBoxSimple.Show(win,text,caption,Btns,Img);
                    return Rtn;
                }                
            }
            
            void OnTimerElapsed(object state) {
                IntPtr mbWnd = FindWindow(null, _caption); // lpClassName is #32770 for MessageBox
                if(mbWnd != IntPtr.Zero)
                    SendMessage(mbWnd, WM_CLOSE, IntPtr.Zero, IntPtr.Zero);
                _timeoutTimer.Dispose();
            }

        }
​
​