viewbag in a dropdownlist

Question

i'm a beginner in MVC

I try to display a viewbag in a drop down list.

Here is what I get in my controller :

 public ActionResult TableauPolyvalence()
    {
        List<Batiments> BatimentList = _context.Batiments.ToList();
        ViewBag.BatimentList = new SelectList(BatimentList, "Id_Batiment", "Nom");
        return View();
    }

Here is my view :

  @if (ViewBag.BatimentList != null)
            {
                @Html.DropDownListFor(model => model.Batiment, (SelectList)ViewBag.BatimentList, "-- Sélectionner le bâtiment --", new { @class = "form-control" })
            }

I get the following message error : System.NullReferenceException: 'Object reference not set to an instance of an object.' I tried different way in my View but it doesn't work

Can somoene help me for this please

Does this answer your question? [What is a NullReferenceException, and how do I fix it?](https://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — Progman, Jun 07 '22 at 14:17
check your markup, make sure you dont have duplicate model names — Henry24, Jun 07 '22 at 14:37

Ruikai Feng · Answer 1 · 2022-06-08T05:23:07.900

0

It may help if you could show the details of your models and I suppose This error was caused by

ViewBag.BatimentList = new SelectList(BatimentList, "Id_Batiment", "Nom");

when you construct a new selectlist,it takes "Id_Batiment" property as value field and"Nom" property as text filed,if your model don't have the property with the same name ,Text field or Value field will be null,and you'll get the error you've shown

And I tested twice as below, you could see the result:

test1:

test2:

edited Jun 08 '22 at 05:23

answered Jun 08 '22 at 03:31

Ruikai Feng

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Thank you very much !! I refered to my database column who was "Id_Batiment" and not in my model who was "IdBatiment" thank you ! – DimitriB Jun 08 '22 at 06:43

viewbag in a dropdownlist

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