void DemoSelectLine (HANDLE hLcWnd)
{
  HANDLE hEnt;
  double Len;
  WCHAR  szText[256];
  int Ret;
m1:
  Ret = lcWndPickEnt( hLcWnd, L"My command", L"Select Line" );
  if (Ret == 1){
    // some entity has been picked
    hEnt = lcPropGetHandle( hLcWnd, LC_PROP_WND_ENT );
    if (lcEntType( hEnt, LC_ENT_LINE ) == TRUE){
      Len = lcPropGetFloat( hEnt, LC_PROP_LINE_LEN );
      swprintf( szText, L"Line length = %.2f", Len );
      lcWndMessage( hLcWnd, szText, LC_MB_OK );
    }else{
      lcWndMessage( hLcWnd, L"Not a line", LC_MB_OK );
    }
    // pick another entity
    goto m1;
  }else{
    // Ret == 2 - right button has been pressed
    // Ret == 3 - <Esc> key has been pressed
  }
}