ASP.NET MVC - Object reference not set to an instance of an object

Question

I have recently taken over support of an ASP.NET MVC project, and am trying to work through some of the errors, one in particular has me stumped though.

We have a 'New' page to add new items, with the following code running when the page is posted:

[HttpPost]
public ActionResult New(RecordView i)
{
    if(ModelState.IsValid)
    {
        repository.AddRecord(i.DogIncident);

        return View("Index");
    }
    return View("Index");
}

However, when it tries to load the Index view, I get the following error: "Object reference not set to an instance of an object." and it points to the following block of code at the top of a file called RecordsView.cshtml:

@for (var i = 0; i < Model.Records.Count; i++)

The record does add correctly though, it just doesn't load the listings page correctly, and since this is just a "nice to have" I thought I'd simplify things by changing it so that it either returns some text which generates an error as it's expecting a boolean returned.

Any ideas on how to fix this please? I'm stumped.

Thanks!

You're trying to access a model in your view, but you're not passing any. — Jeroen Vannevel
– Jeroen Vannevel, Commented Jan 9, 2014 at 16:29
You're not passing a model when calling return View("Index"); you need something like return View("Index", someModel); — the_lotus
– the_lotus, Commented Jan 9, 2014 at 16:32
Thank you, please pardon my ignorance but I am importing my models with the 'using' statement at the top of the page, and I want to include one called 'Foo' for example, I'd do View("Index", Foo) ? it's just that it's generating an error for me — Nick
– Nick, Commented Jan 9, 2014 at 16:35
@Nick: create a new object of type Foo: return View("Index", new Foo());. — Jeroen Vannevel
– Jeroen Vannevel, Commented Jan 9, 2014 at 16:38

John H · Accepted Answer · 2014-01-09 16:49:48Z

The flow of your code here doesn't look right:

[HttpPost]
public ActionResult New(RecordView i)
{
    if(ModelState.IsValid)
    {
        repository.AddRecord(i.DogIncident);

        return View("Index");
    }
    return View("Index");
}

From your description above, it sounds as though you're POSTing from your New view, to this New action, which should then redirect, when successful, to your Index action. Currently, the above code is not doing that, and it also fails to redisplay the form if the model isn't valid. It should probably look more like this:

[HttpPost]
public ActionResult New(RecordView i)
{
    if(ModelState.IsValid)
    {
        repository.AddRecord(i.DogIncident);

        return RedirectToAction("Index");
    }

    // Redisplay the `New` view, passing the model
    // back to it in order to repopulate the form
    return View(i);
}

The important distinction between return View(...) and return RedirectToAction(...) is that the latter will run the action and return the associated view. The former will simply return the view. That has implications in that if the Index action builds a model, and passes it to the Index view, none of that will happen if you simply return the view.

You could of course do something like:

return View("Index", new YourModelType());

but that isn't going to work if, as discussed above, your Index action performs some other data construction for your model, such as building drop down lists, which new YourModelType() wouldn't do.

Also, when data that is sent to a POST action is valid, you should be redirecting to another action (as I've done above), rather than simply returning a view, in order to conform with the Post-Redirect-Get pattern, which prevents some types of duplicate form submissions.

in my case difference of return View(...) and return RedirectToAction(...) was the problem. I've used return View() which was not calling action method in my controller

Sergey Litvinov · Accepted Answer · 2014-01-09 16:46:29Z

2

You display Index view, and seems that it requires some Model - Model.Records. And you don't pass it in this HttpPost action.

If you have action for that Index page, then you can just do

[HttpPost]
public ActionResult New(RecordView i)
{
    if(ModelState.IsValid)
    {
        repository.AddRecord(i.DogIncident);

        return RedirectToAction("Index");
    }
    return View(i);
}

It will just redirect a user to Index view, after creation of new RecordView item

edited Jan 9, 2014 at 16:46

answered Jan 9, 2014 at 16:29

Sergey Litvinov

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Comments

Murali Murugesan · Accepted Answer · 2014-01-09 16:57:25Z

2

Basically you may are trying to achieve PRG(Post/Redirect/Get) modal.

I guess, the problem is you are not sending the model for your GET request.

Post--> Save --> Redirect --> Load Data -->Assign to View in Index -->Access in view

//POST & REDIRECT

[HttpPost]
public ActionResult New(RecordView i)
{
    if(ModelState.IsValid)
    {
        repository.AddRecord(i.DogIncident);

        return RedirectToAction("Index");
    }
}

//GET

public ActionResult Index()
{
 var model=new MyViewModel();

 model.Records=repository.GetRecords(i.DogIncident);

 return View(model); //Assign to View in Index
}

Index.cshtml

 @model MyViewModel

 @for (var i = 0; i < Model.Records.Count; i++)

edited Jan 9, 2014 at 16:57

answered Jan 9, 2014 at 16:51

Murali Murugesan

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Comments

Matt Millican · Accepted Answer · 2014-01-09 16:30:35Z

1

If Records is a list, make sure your ViewModel has a constructor:

public class RecordView
{
    public List<Record> Records { get; set; }

    public RecordView()
    {
        Records = new List<Record>();
    }
}

answered Jan 9, 2014 at 16:30

Matt Millican

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2 Comments

Sergey Litvinov Over a year ago

I think it won't work, as Index page should have some model. and your answer will just remove NRE, but that page won't display any data.

Nick Over a year ago

Thank you, it is passing the information I think because if you go to /Home/ it loads everything fine, it's only when it's routed from /Home/New/ that it generates an error

ElliotSchmelliot · Accepted Answer · 2014-01-09 19:15:47Z

1

You mentioned that the record adds correctly, so you must be passing a valid record model into your view from some other action than the one provided.

If @for (var i = 0; i < Model.Records.Count; i++) is the cause of this error, my guess is that the model exists, but the Records property has not been set. One immediate work around would be checking the existence of this property before accessing it. For example:

if (Model.Records != null) {
    for (var i = 0; i < Model.Records.Count; i++) .....
}

answered Jan 9, 2014 at 19:15

ElliotSchmelliot

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Comments

Muhammad Mustafa · Accepted Answer · 2016-04-17 19:05:34Z

0

i think you have collections are not instantiated, the error may be in models not in view models. this because when ever you have a collection you need to instantiate inside of constructor of that entity.

answered Apr 17, 2016 at 19:05

Muhammad Mustafa

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Comments

user14105450 · Accepted Answer · 2020-08-14 13:14:35Z

0

May be this is your answer...!Just look

   [HttpPost]

   public ActionResult New(RecordView)

   {
      if(ModelState.IsValid)

    {  
       repositry.AddRecord(i.DogIncident);

       return RedirectToAction("Index");
    }
  }

edited Aug 14, 2020 at 13:14

answered Aug 14, 2020 at 13:09

user14105450

12 bronze badges

1 Comment

Jeremy Caney Over a year ago

Please be sure to review the existing answers before contributing your own. In this case, the OP accepted an answer that looks very similar to this nearly seven years ago—except they provided far more explanation and detail. Given that, it's not clear this adds much to the conversation. By all means, feel free to contribute new answers to old questions, even if they've already been answered. But when you do so, be sure to call out why you're answer is different from the existing answers, and offer something new.

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