How to add data into List<T> in ASP.NET MVC 4.0?

Question

I am new in MVC.
I have a class in Models like below.

public class UserInfo
{
  public string Name{get;set;}
  public string Surname{get;set;}
}

And I have a controller like this.

public class HomeController : Controller
    {
    //
    // GET: /Home/

    List<UserInfo> Users = new List<UserInfo>(); 
    public ActionResult Index()
    {
        return View();
    }

   public ActionResult Create()
    {
        return View();
    }

    [HttpPost]
    public ActionResult Create(UserInfo userInfo)
    {
        if (ModelState.IsValid)
        {
            Users.Add(userInfo);
            return RedirectToAction("Index");
        }
        return View();
    }

}

And every time when i press Create button in browser, it redirects to Index View. But List<UserInfo> is empty. Why it happens? How to save data into List and show from grid or table from that List?

It's because you're not persisting the model and not passing it around. — Daniel Imms
– Daniel Imms, Commented Jan 22, 2014 at 19:35

Maess · Accepted Answer · 2014-01-22 19:43:28Z

3

Controllers are stateless. A new instance is created each time you call an action, this is why your list is always empty.

If you want to persist the list between controller actions, you will need some sort of persistence mechanism - database, caching, etc.

edited Jan 22, 2014 at 19:43

answered Jan 22, 2014 at 19:36

Maess

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Comments

Masoud Darvishian · Accepted Answer · 2017-09-24 22:40:19Z

1

Make your list static

static List<UserInfo> Users = new List<UserInfo>();

answered Sep 24, 2017 at 22:40

Masoud Darvishian

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Comments

mckennawebdev · Accepted Answer · 2014-01-22 19:42:59Z

1

I believe Maess pointed out the details first.

Even though your [HTTPPost] Create action adds the new user to the List object, there does not appear to be any means to save the entered data to persistent storage. Every time you instantiate the controller, the List object will be empty, as you have currently coded it.

If you want the data stored to a database, check out this tutorial from asp.net for one method:

http://www.asp.net/mvc/tutorials/mvc-4/getting-started-with-aspnet-mvc4/accessing-your-models-data-from-a-controller

answered Jan 22, 2014 at 19:42

mckennawebdev

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Daniel Melo · Accepted Answer · 2014-01-22 19:53:55Z

1

In your view put this reference for object:

Inherits="System.Web.Mvc.ViewPage<List<UserInfo>>" %>

And in your class change this:

List<UserInfo> Users = new List<UserInfo>();
    public ActionResult Index()
    {
        return View(Users);
    }

but for you to save the list data in memory, you'd better declare the List object as static, because then he retains the information already added. For example:

 public class HomeController : Controller
    {
        public static List<UserInfo> Users = null; 

        //
        // GET: /Home/

        public ActionResult Index()
        {
            return View(Users);
        }

        public ActionResult Create()
        {
            return View();
        }

        [HttpPost]
        public ActionResult Create(UserInfo userInfo)
        {
            if (ModelState.IsValid)
            {
                Users.Add(userInfo);
                return RedirectToAction("Index");
            }
            return View();
        }

    }

answered Jan 22, 2014 at 19:53

Daniel Melo

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2 Comments

AbhiJA Over a year ago

sir here how can I check if (Model.Users.Count() != null) inside view html page?

Daniel Melo Over a year ago

@AbhiJA Hi, just check the Model like this if(Model.Count >0) I'm supposing that you're using the list as Model.

Karan · Accepted Answer · 2017-09-25 10:30:09Z

1

Everytime you create a List<T> with new keyword it's instance is created which doesn't have any kind of data, so get data from database using your DatabaseContext and bind it to your list like this:

List<UserInfo> Users = new List<UserInfo>();
Users.Add(_databasecontext.Users.ToList());

and return it to the view.

answered Sep 25, 2017 at 10:30

Karan

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