hair/description/toolhairselection.hParameters are accessed with cinema::C4DAtom::GetParameter() and cinema::C4DAtom::SetParameter(). See Parameters.
Parameter: Mode
HAIR_SELECTION_MODEHAIR_SELECTION_MODE_NEWHAIR_SELECTION_MODE_ADDHAIR_SELECTION_MODE_REMOVEParameter: Select
HAIR_SELECTION_SELECTHAIR_SELECTION_SELECT_UNROOTEDHAIR_SELECTION_SELECT_INTERSECTINGHAIR_SELECTION_SELECT_ZEROParameter: Invert
HAIR_SELECTION_INVERT