class Program

 {

 private const uint WM_SYSCOMMAND = 0x112; //系统消息

 private const int SC_MONITORPOWER = 0xF170; //关闭显示器的系统命令

 private const int MonitorPowerOff = ; //2为PowerOff, 1为省电状态，-1为开机

 private static readonly IntPtr HWND_BROADCAST = new IntPtr(0xffff);//广播消息，所有*窗体都会接收

 [DllImport("user32.dll")]

 private static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, int wParam, int lParam);

 static void Main(string[] args)

 {

 SendMessage(HWND_BROADCAST, WM_SYSCOMMAND, SC_MONITORPOWER, MonitorPowerOff);

 }

 }