...select a row in a Memo by clicking on it?

procedure TfrmMain.Memo1Click(Sender: TObject);
var
  Line: Integer;
begin
  with (Sender as TMemo) do
  begin
    Line      := Perform(EM_LINEFROMCHAR, SelStart, 0);
    SelStart  := Perform(EM_LINEINDEX, Line, 0);
    SelLength := Length(Lines[Line]);
  end;
end;