One to Many View - do I have to use a View Model?

Question

Say I have a view like this:

@model Models.CustomerModel

@{
    ViewBag.Title = "Details";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Details</h2>

<div>
    @*<h4>ApplicationModel</h4>*@
    <hr />
    <dl class="dl-horizontal">
        <dt>
            @Html.DisplayNameFor(model => model.FirstName)
        </dt>

        <dd>
            @Html.DisplayFor(model => model.FirstName)
        </dd>

        <dt>
            @Html.DisplayNameFor(model => model.Surname)
        </dt>

        <dd>
            @Html.DisplayFor(model => model.Surname)
        </dd>
       </dl>
</div>

Say CustomerModel also has a collection of Orders. The Order class looks like this:

public class Order {
public int OrderID {get; set; }
public datetime OrderDate {get; set; }

How can I put all the Orders liked to the Customer on the same view? I have tried this (under the code above):

<table class="table">
    <tr>
        <th>
            @Html.DisplayNameFor(model => model.OrderID)
        </th>
    <th>
            @Html.DisplayNameFor(model => model.OrderDate)
        </th>
    </tr>

@foreach (var item in model.Orders)
{
    <tr>
        <td>
            @Html.DisplayFor(item => item.OrderID)
        </td>
    <td>
            @Html.DisplayFor(item => item.Description)
        </td>
    </tr>
}

The error I get is:

The parameters dictionary contains a null entry for parameter 'orderid' of non-nullable type 'System.Int32' for method 'System.Web.Mvc.ActionResult Delete(Int32)'.

If I remove the second fragment of code (for each loop), then it works properly. How do I add the second fragment of code?

Using `foreach` is Ok. Where is the problem? Doesn't it work? — Roman Marusyk, Aug 01 '17 at 09:06
Your heading is somehow unrelated to the question, maybe I'm misunderstanding something. What's the problem? — jAC, Aug 01 '17 at 09:08
The error is related to calling your `Delete()` method (and that has nothing to do with the code you have shown) — , Aug 01 '17 at 09:34
similar issue maybe related this one: https://stackoverflow.com/questions/23245365/mvc-the-parameters-dictionary-contains-a-null-entry-for-parameter-k-of-non-n — jyrkim, Aug 01 '17 at 09:37

Roman Marusyk · Accepted Answer · 2017-08-01T09:34:10.963

0

Try add null check

@if(Model.Orders != null)
{
  foreach (var item in Model.Orders)
  {
      <tr>
          <td>
              @Html.DisplayFor(t => item.OrderID)
          </td>
      <td>
              @Html.DisplayFor(t => item.Description)
          </td>
      </tr>
  }
}

or using LINQ you can

if(Model.Orders.Any())

if it doesn't help then see this question

edited Aug 01 '17 at 09:34

answered Aug 01 '17 at 09:19

Roman Marusyk

23,328
24
73
116

The error I get with this is: "CS0103: The name 'model' does not exist in the current context" – w0051977 Aug 01 '17 at 09:25
1

Because it has to be `Model` – jAC Aug 01 '17 at 09:25
Ohh, yes. Use "Model" not "model" – Roman Marusyk Aug 01 '17 at 09:25
It now says: "A local or parameter named 'item' cannot be declared in this scope because that name is used in an enclosing local scope to define a local or parameter" – w0051977 Aug 01 '17 at 09:30
1

`@Html.DisplayFor(m => item.Description)`. You cannot declare a new `item` in your lambda, if it's already used. – jAC Aug 01 '17 at 09:32
@w0051977 You did change it on both `DisplayFor`, didn't you? – jAC Aug 01 '17 at 09:35
@jAC, I rebuilt the project and it is working now. Thanks. What is m in the lambda expression? It is passed as an input parameter but is not used. – w0051977 Aug 01 '17 at 09:38
1

@w0051977 The part of the lambda before `=>` (here `t` or `m`) declares a variable, that references the `Model`, since `DisplayFor` usually directly should reference some `Model.Property` (e.g. `Html.DisplayFor(m => m.FirstName)`. This is a workaround to make `DisplayFor` work in a loop. If you're uncomfortable with it, simply use `Html.Display(item.Property)`. See: https://stackoverflow.com/questions/3419711/how-can-i-use-html-displayfor-inside-of-an-iterator – jAC Aug 01 '17 at 09:42

score 0 · Answer 2 · answered Aug 01 '17 at 09:30

0

You can make OrderId Nullable in CustomerModel

public int? OrderID {get; set; }

OR check the Null value coming from Database for OrderId (If OrderId is not supposed to be Null then it's bad data and should be restricted from database itself)

answered Aug 01 '17 at 09:30

Faisal.lh

29
5

One to Many View - do I have to use a View Model?

2 Answers2