一次清除 GroupBox 裡所有 CheckBox.Checked 狀態

procedure TMainForm.btnClearClick(Sender: TObject);
var
  i: Integer;
begin
  for i := 0 to GB2.ControlCount-1 do
    if GB2.Controls[i].ClassNameIs('TCheckBox') then
      TCheckBox(Gb2.Controls[i]).Checked:=False;
end;