Object reference not set to an instance of an object MVC

Question

this is my models:

public class Ressource
{
    [Key]
    public int RessourceId { get; set; }
    public string TitreR { get; set; }
    public string Link { get; set; }
    public string Type { get; set; }
    public string Desc { get; set; }
    public int Position { get; set; }
    public int Rating { get; set; }
    public string Tags { get; set; }
    public int SectionId { get; set; }
    public int UserId { get; set; }

}
public class Section
{
    [Key]
    public int SectionId { get; set; }
    public string Titre { get; set; }
    public String Tags { get; set; }

    public virtual ICollection<Ressource> Ressources { get; set; }

}
public class structure
{

        public Ressource ress;
        public List<string> liste;

}

In this view, I enter the resource's title (TitreR), a description (Desc) and I choose from a list of tags which ones I want to link with this resource as well as entering a tag:

@model Mocodis.Models.structure

@{
    ViewBag.Title = "AjouterRessource";
}

<h2>AjouterRessource</h2>

@using (Html.BeginForm("AjouterRessource", "Home", FormMethod.Post))
{
@Html.AntiForgeryToken()
@Html.ValidationSummary(true)

<fieldset>
    <input type="hidden" name="SectionId" value="@Model.ress.SectionId"  />
    <legend>Ressource</legend>

    <div class="editor-label">
        @Html.LabelFor(model => model.ress.TitreR)
    </div>
    <div class="editor-field">
        @Html.EditorFor(model => model.ress.TitreR)
        @Html.ValidationMessageFor(model => model.ress.TitreR)
    </div>

    <div class="editor-label">
        @Html.LabelFor(model => model.ress.Desc)
    </div>
    <div class="editor-field">
        @Html.EditorFor(model => model.ress.Desc)
        @Html.ValidationMessageFor(model => model.ress.Desc)
    </div>
</fieldset>
}
    <form id="orderProductForm219" name="orderProductForm219" method="post" >
<b>Choisir les mots clés:</b> 
<br /><br />


@foreach (string s in @Model.liste)
{
    <input type="checkbox" name="tags[]" value="@s"> @s<br />
}
<input type="text" name="tags" id="tags" value="" /> 


    <p>
        <input type="submit" value="Create" />
        <input type="hidden" name="tag" value="tags" />
        <input type="hidden" name="res" value="@Model.ress" />
    </p></form>

(I didnt put the javascript for it)

Finally the controllers are:

public ActionResult AjouterRessource(int SectionId)
    {

        Ressource res = new Ressource();
        res.SectionId = SectionId;
        Section sec = _db.Sections.Where(r => r.SectionId == SectionId).FirstOrDefault();
        char[] delimiterChars = { ' ', ',', '.', ':', '\t' };
        List<string> l = new List<string>();
        l = sec.Tags.Split(delimiterChars).ToList();

        structure s = new structure();
        s.ress = res;
        s.liste = l;

        return View(s);

    }

    public string Check ( string list, string s)
    {
        char[] delimiterChars = { ' ', ',', '.', ':', '\t' };
        List<string> l = new List<string>();
        List<string> liste = new List<string>();
        l = s.Split(delimiterChars).ToList();
        liste = list.Split(delimiterChars).ToList();
        foreach (string item in l)
        {
            if (!liste.Contains(item))
                liste.Add(item);
        }
        return  (string.Join(" ", liste.ToArray()));
    }

    [Authorize]
    [HttpPost]
    [InitializeSimpleMembership]
    public ActionResult AjouterRessource(Ressource res, int SectionId, string tag)
    {
        if (ModelState.IsValid)
        {

            res.SectionId = SectionId;
            var model = _db.Sections.Where(c => c.SectionId == SectionId).FirstOrDefault();
            res.Tags = tag;
            model.Tags = Check(model.Tags, tag);
            _db.Entry(model).State = EntityState.Modified;
            _db.Entry(res).State = EntityState.Added;
            _db.SaveChanges();
            return RedirectToAction("Section", new { SectionId = SectionId });
        }
        return View();

    }

I keep getting: Object reference not set to an instance of an object on the line: @Html.ValidationSummary(true) in my view. Can you tell me how to fix it please?

Thank you

Answer 1

Every time I have gotten that error it has been from not initializing something. Looking through your code the only spot I am seeing that might need it is when you are setting structure. You might try putting a constructor on that class to initialize the fields and see if that helps. something like

public structure()
{
ress = new Resource();
liste = new List<string>();
}    

You probably need to add the { get; set; } to the resource and list under structure as well. Hopefully this helps.