ASP.Net MVC5 – "Resource Cannot be found" error

Question

newbie here. I get the error The resource cannot be found. when requesting url /event/details/3. I use a MVVM.

My schema is simple. I have "Event", "Person" and "PersonInEvent" tables. "PersonInEvent" is a junction table for the two others (holds the foreign keys).

I am trying to display in the "Details" view the event's data with its id (/event/details/3). The event's id is passed to the "Details" controller action, which instantiates my ViewModel that hold an event object. I set this event to be the one with the id that I receive when the viewmodel is created.

According to my controller (see below) I get the error because vm.Event == null. But I can't find a way to solve this issue. I have the feeling that it is a basic programming problem, such as how my "Event" property in my viewmodel is created. But still I cannot figure out the solution. Thanks in advance.

My controller's Details action:

[HttpPost] // this was the problem
[ValidateAntiForgeryToken]
public ActionResult Details(int id)
    {
        var vm = new EventDetailsViewModel(id);

        if (vm.Event == null)
        {
            return HttpNotFound(); // I get the error because of this imo
        }

        return View("Details", vm);
    }

My view model:

public class EventDetailsViewModel
    {
        private readonly ApplicationDbContext _db = new ApplicationDbContext();

        private readonly int _eventIdVm;
        private Event _event;

        public EventDetailsViewModel(int id)
        {
            _eventIdVm = id;
            _event.EventId = id;
        }

        public Event Event
        {
            get
            {
                return _event = _db.Event.Find(_eventIdVm);
            }

            set { _event = value; }
        }

        public List<Person> Persons
        {
            get
            {
                if (!_db.PersonInEvent.Any(pe => pe.EventId == _eventIdVm))
                {
                    return Enumerable.Empty<Person>().ToList();
                }
                var personsOfEvent = _db.PersonInEvent.Where(pe => pe.EventId == _eventIdVm)
                    .Select(pe => pe.Person)
                    .ToList();
                return personsOfEvent;
            }
        }
    }

My view just in case:

@model BillSplittingWebApp.ViewModels.EventDetailsViewModel

@{
    ViewBag.Title = "Details";
}

<h2>Details</h2>

<div>
    <h4>Event</h4>
    <hr />
    <dl class="dl-horizontal">
        <dt>
            @Html.DisplayNameFor(model => model.Event.EventName)
        </dt>

        <dd>
            @Html.DisplayFor(model => model.Event.EventName)
        </dd>

        <dt>
            @Html.DisplayNameFor(model => model.Event.EvenTimeBegin)
        </dt>

        <dd>
            @Html.DisplayFor(model => model.Event.EvenTimeBegin)
        </dd>

    </dl>
</div>

EDIT: Problem was the attribute [HttpPost] that I forgot to remove for the action.

Answer 1

This is a poor way MVC is a Pattern it's self. ViewModels should not be referencing databases directly. However, the issue is that in your viewModel you have declared a private Event Object. In the constructor you are trying to set the id of this object without first instanciating a new instance.

You can remove this line of code as it's not doing anything useful in the constructor anyway:

 _event.EventId = id;