// retrieve selection information from selection system.
    private bool RetrieveSelectionInfo( UnitSelectionSystem _SelectSys , 
										out SelectInformation _SelectionInfo )
    {
        _SelectionInfo = _SelectSys.GetPrimarySelectInfo() ;

        if( null == _SelectionInfo ||
            false == _SelectionInfo.isValid )
            return false ;

        return true ;
    }