After yet some more research I came upon some tools that assist in the ViewModel process - one being AutoMapper & the other InjectValues. I went with InjectValues primarily because it can not only "flatten" objects (map object a -> b) but it can also "unflatten" them (map object b -> a) - something that AutoMapper unfortunately lacks out-of-the-box - something I need to do in order to update values inside of a DB.
Now, instead of sending my Article model with all of its properties to my views, I created an ArticleViewModel containing only the following properties:
public class ArticleViewModel
{
public int Id { get; set; }
[MaxLength(15)]
public string Type { get; set; }
public bool Active { get; set; }
public bool Stickied { get; set; }
[Required]
[MaxLength(200)]
public string Title { get; set; }
[Required]
[AllowHtml]
public string Body { get; set; }
}
When I Create an Article, instead of sending an Article object (with every property) I send the View a 'simpler' model - my ArticleViewModel:
//
// GET: /Article/Create
public ActionResult Create()
{
return View(new ArticleViewModel());
}
For the POST method we take the ViewModel we sent to the View and use its data to Create a new Article in the DB. We do this by "unflattening" the ViewModel onto an Article object:
//
// POST: /Article/Create
public ActionResult Create(ArticleViewModel articleViewModel)
{
Article article = new Article(); // Create new Article object
article.InjectFrom(articleViewModel); // unflatten data from ViewModel into article
// Fill in the missing pieces
article.CreatedBy = CurrentSession.SamAccountName; // Get current logged-in user
article.DateCreated = DateTime.Now;
if (ModelState.IsValid)
{
_db.Articles.Add(article);
_db.SaveChanges();
return RedirectToAction("Index", "Home");
}
ViewBag.Categories = GetDropDownList();
return View(articleViewModel);
}
The "missing pieces" filled in are Article properties I didn't want to set in the View, nor do they need to be updated in the Edit view (or at all, for that matter).
The Edit method is pretty much the same, except instead of sending a fresh ViewModel to the View we send a ViewModel pre-populated with data from our DB. We do this by retrieving the Article from the DB and flattening the data onto the ViewModel. First, the GET method:
//
// GET: /Article/Edit/5
public ActionResult Edit(int id)
{
var article = _db.Articles.Single(r => r.Id == id); // Retrieve the Article to edit
ArticleViewModel viewModel = new ArticleViewModel(); // Create new ArticleViewModel to send to the view
viewModel.InjectFrom(article); // Inject ArticleViewModel with data from DB for the Article to be edited.
return View(viewModel);
}
For the POST method we want to take the data sent from the View and update the Article stored in the DB with it. To do this we simply reverse the flattening process by 'unflattening' the ViewModel onto the Article object - just like we did for the POST version of our Create method:
//
// POST: /Article/Edit/5
[HttpPost]
public ActionResult Edit(ArticleViewModel viewModel)
{
var article = _db.Articles.Single(r => r.Id == viewModel.Id); // Grab the Article from the DB to update
article.InjectFrom(viewModel); // Inject updated values from the viewModel into the Article stored in the DB
// Fill in missing pieces
article.LastUpdatedBy = MyHelpers.SessionBag.Current.SamAccountName;
article.LastUpdated = DateTime.Now;
if (ModelState.IsValid)
{
_db.Entry(article).State = EntityState.Modified;
_db.SaveChanges();
return RedirectToAction("Index", "Home");
}
return View(viewModel); // Something went wrong
}
We also need to change the strongly-typed Create & Edit views to expect an ArticleViewModel instead of an Article:
@model ProjectName.ViewModels.ArticleViewModel
And that's it!
So in summary, you can implement ViewModels to pass just pieces of your Models to your Views. You can then update just those pieces, pass the ViewModel back to the Controller, and use the updated information in the ViewModel to update the actual Model.
