如何添加ABPerson至ABGroups在MonoTouch中？我用ABGroup.Add()以下异常触发UnhandledException:System.ArgumentException:cfErrorHandlemustnotbenull.Parametername:cfErrorHandle我使用ABPeoplePickerNavigationController选择已经存在的ABPerson。ABAddressBookadBook=newABAddressBook();//ABPeoplePickerNavigationControllerSelectPersoneven