public void RemoveContactFromFavoriteGroup(Contact contact)
{
if (contact.Guid == Guid.Empty)
throw new InvalidOperationException("This is not a valid Messenger contact.");
ContactGroup favGroup = NSMessageHandler.ContactGroups.FavoriteGroup;
if (favGroup != null && contact.HasGroup(favGroup))
RemoveContactFromGroup(contact, favGroup);
else
throw new InvalidOperationException("No favorite group");
}
