How pass a model to a view .NET Core Entity Framework

Question

I try to learn Entity Framework and I like to understand a basic concept.

In a test program I have this code:

ApplicationDbContext.cs

  public class ApplicationDbContext : DbContext
  {
        public DbSet<Book> Books { get; set; }
  }

BooksController.cs

public IActionResult Index()
{
    ViewBag.Books = _db.Books.ToList();
    return View();
}

index.cshtml

<br />
<div class="container row p-0 m-0">
    <div class="col-6">
        <h2 class="text-info">Book List</h2>
    </div>
    <div class="col-3 offset-3">
        <a asp-action="Upsert" asp-controller="Books" class="btn btn-info form-control text-white">
            Add New Book
        </a>
    </div>

    <div class="col-12 border p-3">
        <table id="DT_load" class="table table-striped table-bordered" style="width:100%">
            <thead>
                <tr>
                    <th>Name</th>
                    <th>Author</th>
                    <th>ISBN</th>
                    <th>IdCat</th>
                    <th>DescCat</th>
                    <th></th>
                </tr>

                @foreach (var book in ViewBag.Books)
                {
                <tr>
                    <td>@book.Name</td>
                    <td>@book.Author</td>
                    <td>@book.ISBN</td>
  
                    <td>
                        <div class="text-center">
                            <a href="/Books/Upsert?id=@book.Id" class='btn btn-success text-white' style='cursor:pointer; width:70px;'>
                                Edit
                            </a>
                            &nbsp;
                            <a class='btn btn-danger text-white' style='cursor:pointer; width:70px;'
                               onclick= "/books/Delete?id=@book.Id">
                                Delete
                            </a>
                        </div>



                    </td>
                </tr>
                }

            </thead>
        </table>
    </div>
</div>

This code works like I expect and show a grid of all books.

But frankly I don't think this is the right way to use controller and models.

I like to pass the list in the view:

   return View(_db.Books.ToList());

or with another format and use it as model by adding in the index.cshtml a line like this:

@model "my parameter"

In short at the place of ViewBag I like to use a model.

First of all, I ask: Is correct what I like to do?

Or in this case I can keep the ViewBag because the code work and this approach is correct?

This question, is not only to find a worked solution, but to find the best practice to follow the MVC concepts.

Thanks !

Answer 1

You can try it as follows.

Your controller

public IActionResult Index()
{
    var books = _db.Books.ToList();
    return View(books);
}

View

@model IEnumerable<YourNamespace.Models.Book>

@foreach (var book in Model)
{
<tr>
    <td>@book.Name</td>
    <td>@book.Author</td>
    <td>@book.ISBN</td>

    <td>
        <div class="text-center">
            <a href="/Books/Upsert?id=@book.Id" class='btn btn-success text-white' style='cursor:pointer; width:70px;'>
                Edit
            </a>
            &nbsp;
            <a class='btn btn-danger text-white' style='cursor:pointer; width:70px;'
               onclick= "/books/Delete?id=@book.Id">
                Delete
            </a>
        </div>
    </td>
</tr>
}

Answer 2

First of all, I ask: Is correct what I like to do?

Yes, most developers prefer typed view models over ViewBag for non-trivial views. This way the compiler can help you finding typos in your view and IDEs can provide itellisense.

but I need to pass a list or similar not a class

That doesn't matter. You provide an instance of "some class" to your view. If it's a list, "some class" = List<Book> .

 // in your view
 @model System.Collections.Generic.List<MyApp.Models.Book>

 // loop
 @foreach(var book in Model) 

(you'll have to adjust the namespace)

But...

In many cases you'll need more than just the list, so it helps to have a separate view model class, which can be as simple as

public record BooksListViewModel(List<Book> Result);

// in your controler
return View(new BooksListViewModel(books));

// in your view
@model WebApplication1.ViewModels.BooksListViewModel

@foreach(var book in Model.Result)

Note that I've used the new record feature of C# 9. If you're on an older version, you'll have to create a "normal" class with a single property "Result". See https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-9#record-types

Answer 3

The best practice to follow is to create a view model and use that view model for the view. This allows you to add new features down the line with minimal extra work. Generally you will have a different view for add/edit, delete, display, etc.

Model

public class BooksViewModel
{
    public List<Book> books = null;
}

Controller

public IActionResult Index()
{
    var viewModel = new BooksViewModel();
    viewModel.books = _db.Books.ToList();

    return View(viewModel);
}

View

@model BooksViewModel

@foreach (var book in Model.books)
{
    
}

Now if you want to add some other data to this view, you just add it to the model and populate it in the controller.