Object reference not set to an instance of an object when passing object from view to controller

Question

I have went over many similar posts, cant seem to find the reason for my error.

Im trying to pass an object type "Product" from a view to a controller, then check for this item's properties.

the view looks like this -

 <table width="100%" cellpadding="5" cellspacing="2" border="0" style="background-color: White;">
@foreach (var item in Model.products)
               {
        <tr>
            <td>@item.ProductName</td>
            <td>@item.Price</td>
            <td>@item.Quantity</td>
            <td><text><img src="@item.Image" width="250px" height="200px"></img></text></td>
            <td>
                @using (Html.BeginForm("Purchase", "Home", FormMethod.Post, new { Product = item}))
                {
                    <input type="hidden" name="item" value="@item" />
                    <input type="submit" value="Purchase" onclick="return confirm('Purchase @item.ProductName ?')"   />
                   }

            </td>
        </tr>
               }
        </table>

And the controller -

[HttpPost]
        public ActionResult Purchase(Product item)
        {

            if (item.Quantity > 0)
            {
                ProductDAL dal = new ProductDAL();
                foreach (Product obj in dal.Products)
                {
                    if (obj.ProductID.Equals(item.ProductID))
                    {
                        obj.Quantity--;
                    }
                }
                dal.SaveChanges();
                return View("PurchaseSuccess", item);
            }
            Session["check"] = item.ProductName;
            return View("PurchaseFail");
        }

The program stops at if(item.Quantity > 0) due to mentioned error.

Possible duplicate of [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) — VDWWD, Jan 26 '18 at 18:31
I seem to be able to pass a string property of the same item, but not the item itself. — Hellowuvrld, Jan 26 '18 at 18:39
Right, you cannot put an entire complex object into a hidden field. Change your hidden field to be `@item.ProductId` and change the action to accept the id instead of the object. — npearson, Jan 26 '18 at 18:41
please edit your answer to include all of the code in the view. I need to see how you are linking from your view to your model. — Michael Henderson, Jan 26 '18 at 22:04

score 0 · Answer 1 · answered Jan 26 '18 at 19:55

0

You are trying to pass an object in a hidden form field. What would that look like ?

Instead, set all data fields your Product model needs to form fields, for example hiddenFor. Controller will then read the fields and bind them to the model.

answered Jan 26 '18 at 19:55

Niko

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3
9

score 0 · Answer 2 · answered Jan 26 '18 at 20:29

Like I said in the comment, a better approach than trying to pass the entire object is to just use the product Id.

<input type="hidden" name="productId" value="@item.ProductID" />

Then modify your controller action accordingly. I recommend putting a GetProductById() method on your DAL if possible.

[HttpPost]
    public ActionResult Purchase([FromBody] int productId)
    {
        ProductDAL dal = new ProductDAL();
        Product item = dal.GetProductById(productId)

        if (item.Quantity == 0)
        {
            Session["check"] = item.ProductName;
            return View("PurchaseFail");
        }

        item.Quantity--;
        dal.SaveChanges();
        return View("PurchaseSuccess", item);
    }

Object reference not set to an instance of an object when passing object from view to controller

2 Answers2