How can I avoid all this code duplication?

Question

As you can see I have to populate the ViewModel with the List of Tags so that the dropdown can have all the options for the user to select. And I have to do this 2 times for the Create Action and 2 times for the Edit action.

[Authorize]
public ActionResult Create()
{
 var tags = from i in _articleService.GetAllTags()
 select new SelectListItem {Text = i.Name, Value = i.ID.ToString()};
 var model = new CreateArticleViewModel {Tags = tags};
 return View(model);
}
[HttpPost, Authorize]
public ActionResult Create(CreateArticleViewModel model)
{
 if (ModelState.IsValid)
 {
 try
 {
 var currentUser = _userService.GetByUserName(User.Identity.Name);
 var tagIds = model.TagIds.Select(int.Parse);
 var article = _articleService.Create(currentUser, model.Title, model.Body, tagIds);
 return RedirectToAction("ViewArticle", new { id = article.ID });
 }
 catch (Exception ex)
 {
 ModelState.AddModelError("Error", ex.Message);
 }
 }
 var tags = from i in _articleService.GetAllTags()
 select new SelectListItem { Text = i.Name, Value = i.ID.ToString() };
 model.Tags = tags;
 return View(model);
}
[Authorize]
public ActionResult Edit(int id)
{
 var article = _articleService.GetById(id);
 var tags = from tag in _articleService.GetAllTags().ToList()
 select new SelectListItem { Text = tag.Name, Value = tag.ID.ToString(), Selected = article.HasTag(tag)};
 var model = new CreateArticleViewModel {Title=article.Title, Body = article.Body, Tags = tags };
 return View(model);
}
[HttpPost, Authorize]
public ActionResult Edit(CreateArticleViewModel model)
{
 if (ModelState.IsValid)
 {
 try
 {
 //handle article update
 }
 catch (Exception ex)
 {
 //Add ModelState error 
 }
 }
 var tags = from tag in _articleService.GetAllTags().ToList()
 select new SelectListItem { Text = tag.Name, Value = tag.ID.ToString(), Selected = article.HasTag(tag)};
 model.Tags= tags;
 return View(model);
}

Is there a better way?

Answer 1

You could refactor out your tagging into a helper method, as below:

[Authorize]
public ActionResult Create()
{
 var model = new CreateArticleViewModel {};
 TagModel (model, _ => false);
 return View(model);
}
[HttpPost, Authorize]
public ActionResult Create(CreateArticleViewModel model)
{
 if (ModelState.IsValid)
 {
 try
 {
 var currentUser = _userService.GetByUserName(User.Identity.Name);
 var tagIds = model.TagIds.Select(int.Parse);
 var article = _articleService.Create(currentUser, model.Title, model.Body, tagIds);
 return RedirectToAction("ViewArticle", new { id = article.ID });
 }
 catch (Exception ex)
 {
 ModelState.AddModelError("Error", ex.Message);
 }
 }
 TagModel (model, _ => false);
 return View(model);
}
[Authorize]
public ActionResult Edit(int id)
{
 var article = _articleService.GetById(id);
 var model = new CreateArticleViewModel {Title=article.Title, Body = article.Body};
 TagModel (model, tag => article.HasTag (tag));
 return View(model);
}
[HttpPost, Authorize]
public ActionResult Edit(CreateArticleViewModel model)
{
 if (ModelState.IsValid)
 {
 try
 {
 //handle article update
 }
 catch (Exception ex)
 {
 //Add ModelState error 
 }
 }
 TagModel (model, tag => article.HasTag (tag));
 return View(model);
}
private void TagModel (CreateArgicleViewModel model, Predicate<Tag> isSelected)
{
 var tags = from tag in _articleService.GetAllTags()
 select new SelectListItem { Text = tag.Name, Value = tag.ID.ToString(), Selected = isSelected(tag)};
 model.Tags= tags;
}

Answer 2

Recently I've been reading a great series of blog posts by Ayende Rahien discussing how we can limit abstractions in a code base and how to implement a very simple infrastructure to make an abstraction for code reuse. Take a look at one of the posts of these series here. You can find the rest of them on his blog.

• nacho10f: great series of blogposts... I dont see how it relates to my question though.
• Beatles1692: You can use Query abstraction to run a predefined query to get all the tags