Question

i have this controller:

public ActionResult Novo()
{
   var products = context.Product.Select(x => new SelectListItem
   {
      Text = x.Name,
      Value = SqlFunctions.StringConvert((double)x.Id).Trim()
   }).ToList();

   MyViewModel myViewModel= new MyViewModel()
   {
      Products = products
   };

   return View(myViewModel);
}

[HttpPost]
public ActionResult Novo(MyViewModel myViewModel)
   {
      if (ModelState.IsValid)
      {
         ...

         context.SaveChanges();

         return RedirectToAction("Index");
      } else {
         var products = context.Product.Select(x => new SelectListItem
         {
            Text = x.Name,
            Value = SqlFunctions.StringConvert((double)x.Id).Trim()
         }).ToList();

         MyViewModel myViewModel= new MyViewModel()
         {
            Products = products
         };

         return View(myViewModel);
      }
}

I must to populate Products in ViewModel in this two methods.

My ViewModel:

public class MyViewModel
{
   public IEnumerable<SelectListItem> Products { get; set; }
   public string ProductIdSelected { get; set; }
}

My HTML:

<div class="editor-field">
   @Html.DropDownListFor(model => model.ProductIdSelected, Model.Products)
</div>

The problem is in my Controller, i must to populate ViewModel in this two methods. I don’t like that, I don’t like to create a method to populate ViewModel too because when validation fail, the others fields keeps populated, why my Products fields don’t keeps populated too? I think using a method is ugly. Is there a way to avoid to use another method?

Is there a way to populate Producs in my ViewModel only once and cache the list of Products when someone do a Post and the Post is not valid.

If NOT, the better way is to use another method. Thanks.

Answer 1

What’s wrong with creating a separate method to populate your VM (for the GET and for the POST when validation fails)?

[HttpGet]
public ActionResult Novo()
{
    MyViewModel myViewModel= new MyViewModel();
    this.LoadProducts(myViewModel);
    return View(myViewModel);
}

[HttpPost]
public ActionResult Novo(MyViewModel myViewModel)
{
    if (ModelState.IsValid)
    {
         ...

         context.SaveChanges();

         return RedirectToAction("Index");
    }
    else 
    {
         MyViewModel myViewModel= new MyViewModel();
         this.LoadProducts(myViewModel);
         return View(myViewModel);
    }
}

private void LoadProducts(MyViewModel model)
{
    model.Products = context.Product.Select(x => new SelectListItem
    {
        Text = x.Name,
        Value = SqlFunctions.StringConvert((double)x.Id).Trim()
    }).ToList();
}

Additionally, you could provide another parameter for LoadProducts so that it could set the selected item.