[DllImport("user32.dll")]

        static extern bool GetLastInputInfo(ref LASTINPUTINFO plii);

        public static long GetIdleTick()

        {

            LASTINPUTINFO lastInputInfo = new LASTINPUTINFO();

            lastInputInfo.cbSize = Marshal.SizeOf(lastInputInfo);

            if (!GetLastInputInfo(ref　lastInputInfo)) return ;

            return Environment.TickCount - (long)lastInputInfo.dwTime;

        }

        [StructLayout(LayoutKind.Sequential)]

        private struct LASTINPUTINFO

        {

            [MarshalAs(UnmanagedType.U4)]

            public int cbSize;

            [MarshalAs(UnmanagedType.U4)]

            public uint dwTime;

        }