public ActionResult Add(WorkshopEditModel model)
        {
            if (!ModelState.IsValid)
            {
                // Pass the action to the form so it knows to return to Add
                ViewData["Action"] = "Add";

                // Add list of projects and employees to choose from
                LoadListsForEdit(model);

                return(View(model));
            }

            // Provider code must be unique. Validate
            if (!_workshopService.SessionIdentifierIsUnique(model.SessionIdentifier))
            {
                ModelState.AddModelError("", "Session Identifier already used. "
                                         + " Please enter a unique session identifier.");

                // Pass the action to the form so it knows to return to Add
                ViewData["Action"] = "Add";

                // Add list of projects and employees to choose from
                LoadListsForEdit(model);

                return(View(model));
            }

            // Add workshop to db
            model = _workshopService.AddOrUpdate(model);

            return(RedirectToAction(nameof(Details), new { id = model.Id }));
        }