public override bool Save()
    {
        if (_referenceType == ReferenceType.Groups || _referenceType == ReferenceType.GroupUsers)
        {
            Groups groups = new Groups(UserSession.LoginUser);

            foreach (GridDataItem item in gridUsers.Items)
            {
                if (item.Selected)
                {
                    groups.AddGroupUser(int.Parse(item["UserID"].Text), _referenceID);
                }
            }
            return(true);
        }

        return(false);
    }