public ActionResult _InsertGroupUser(string groupID)
        {
            int groupIntID;
            try
            {
                groupIntID = Convert.ToInt32(groupID);
            }
            catch (Exception)
            {
                return ErrMsgView("Sorry - An invalid Group ID was used to insert a user.");
            }

            UserLookupViewModel viewUser = new UserLookupViewModel();
            if (TryUpdateModel(viewUser))
            {
                var addUser = (from u in PrdnDBContext.Users
                              where u.ID == viewUser.ID
                              select u).FirstOrDefault();

                if (addUser != null)
                {
                    var group = (from g in PrdnDBContext.Groups
                                 where g.ID == groupIntID
                                 select g).FirstOrDefault();

                    if (group != null)
                    {
                        group.Users.Add(addUser);
                        PrdnDBContext.SaveChanges();
                    }
                    else
                    {
                        ModelState.AddModelError("ID", "invalid group ID");
                    }
                }
                else
                {
                    ModelState.AddModelError("ID", "invalid user ID");
                }
            }

            return View(GroupUserGridList(groupIntID));
        }
        public ActionResult _DeleteGroupUser(string groupID)
        {
            int groupIntID;
            try
            {
                groupIntID = Convert.ToInt32(groupID);
            }
            catch (Exception)
            {
                return ErrMsgView("Sorry - An invalid Group ID was used to insert a user.");
            }

            UserLookupViewModel viewUser = new UserLookupViewModel();
            if (TryUpdateModel(viewUser))
            {
                Group grp = (from g in PrdnDBContext.Groups
                               where g.ID == groupIntID
                               select g).FirstOrDefault();

                if (grp != null)
                {
                    User user = (from u in grp.Users
                                 where u.ID == viewUser.ID
                                 select u).FirstOrDefault();

                    if (user != null)
                    {
                        grp.Users.Remove(user);
                        PrdnDBContext.SaveChanges();
                    }
                    else
                    {
                        ModelState.AddModelError("ID", "User ID "+viewUser.ID.ToString()+" was not a member of group "+grp.Name+".");
                    }
                }
                else
                {
                    ModelState.AddModelError("ID", "invalid group ID");
                }
            }
            return View(GroupUserGridList(groupIntID));
        }