在程序中打开/关闭monitor or lcd

• hWnd

  Handle to the window whose window procedure will receive the message. If you don't want to bother creating a window to send the message to, you can send the message to all top level windows (HWND_BROADCAST) or you can use GetDesktopWindow function sending the message to the desktop window.

• Msg

  Specifies the message to be sent (WM_SYSCOMMAND).

• wParam

  Specifies additional message-specific information (SC_MONITORPOWER).

• lParam
  • 1 - the display is going to low power.
  • 2 - the display is being shut off.
  • -1 - the display is being turned on (undocumented value).

// 关闭 monitor
Sleep(500); // Eliminate user's interaction for 500 ms
SendMessage(HWND_BROADCAST, WM_SYSCOMMAND, SC_MONITORPOWER, (LPARAM) 2);
// 打开 monitor
SendMessage(HWND_BROADCAST, WM_SYSCOMMAND, SC_MONITORPOWER, (LPARAM) -1);
// 电池模式,低电量

Sleep(500); // Eliminate user's interaction for 500 ms
SendMessage(HWND_BROADCAST, WM_SYSCOMMAND, SC_MONITORPOWER, (LPARAM) 1);

ref
 vc版本: http://www.codeproject.com/KB/system/display_states.aspx
C# 版本: http://www.codeproject.com/KB/cs/Monitor_management_guide.aspx