public ActionResult AddActivity(AddActivityViewModel viewModel)
        {
            if (activitiesService.IsValidModelState())
            {
                Activity activity = new Activity();
                activity.ActivityId = 0;
                activity.Duration   = viewModel.Duration;
                activity.Name       = viewModel.Name;
                activity.Price      = viewModel.Price;
                if (activitiesService.IsExistingActivity(a => a.Name == activity.Name))
                {
                    return(View(viewModel));
                }

                bool hasSuccessfullySaved = activitiesService.Add(activity);
                if (hasSuccessfullySaved)
                {
                    TempData["SuccessfullMessage"] = "Activity added successfully!";
                    return(RedirectToAction("ViewActivities", "Activities"));
                }
                else
                {
                    TempData["ErrorMessage"] = "There was a server error during the save of the activity. Try again!";
                    return(RedirectToAction("Index", "Home"));
                }
            }

            return(View(viewModel));
        }