javascriptasp.net-mvcmodel-bindingasp.net-mvc-partialviewbegincollectionitem

A Partial View passing a collection using the Html.BeginCollectionItem helper


I made a small project to understand the answer from Stephen Muecke here: Submit same Partial View called multiple times data to controller?

Almost everything works. The javascript adds new fields from the Partial View, and I can tell they're bound to the model by the "temp" values inserted by the controller method for the partial view.

However, when I submit the new fields the AddRecord() method throws an exception showing that the model isn't getting passed in ("Object reference not set to an instance of an object").

Also, when I view the page source, the BeginCollectionItem helper is inserting a hidden tag as it should around the table in the main view that displays pre-existing records, but not around the new fields that the javascript adds.

What am I doing wrong? I'm pretty new at this so thanks for your patience!

My main view:

@model IEnumerable<DynamicForm.Models.CashRecipient>

@using (Html.BeginForm("AddDetail", "CashRecipients", FormMethod.Post))
{
    @Html.AntiForgeryToken()
    <div id="CSQGroup">
    </div>
}

<div>
    <input type="button" value="Add Field" id="addField" onclick="addFieldss()" />
</div>

<script>
    function addFieldss()
    {   
        //alert("ajax call");
        $.ajax({
            url: '@Url.Content("~/CashRecipients/RecipientForm")',
            type: 'GET',
            success:function(result) {
                //alert("Success");
                var newDiv = document.createElement("div"); 
                var newContent = document.createTextNode("Hi there and greetings!"); 
                newDiv.appendChild(newContent);  
                newDiv.innerHTML = result;
                var currentDiv = document.getElementById("div1");  
                document.getElementById("CSQGroup").appendChild(newDiv);
            },
            error: function(result) {
                alert("Failure");
            }
        });
    }
</script>

My Partial View:

@model DynamicForm.Models.CashRecipient
@using HtmlHelpers.BeginCollectionItem

@using (Html.BeginCollectionItem("recipients"))
{
    <div class="editor-field">
        @Html.LabelFor(model => model.Id)
        @Html.LabelFor(model => model.cashAmount)
        @Html.TextBoxFor(model => model.cashAmount)
        @Html.LabelFor(model => model.recipientName)
        @Html.TextBoxFor(model => model.recipientName)
    </div>
    <div class="form-group">
        <div class="col-md-offset-2 col-md-10">
            <input type="submit" value="Save" class="btn btn-default" />
        </div>
    </div>
}

My model:

public class CashRecipient
{
    public int Id { get; set; }
    public string cashAmount { get; set; }
    public string recipientName { get; set; }  
}

In my controller:

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult AddDetail([Bind(Include = "Id,cashAmount,recpientName")] IEnumerable<CashRecipient> cashRecipient)
{
    if (ModelState.IsValid)
    {
        foreach (CashRecipient p in cashRecipient) {
            db.CashRecipients.Add(p);
        }
        db.SaveChanges();
        return RedirectToAction("Index");

    }

    return View(cashRecipient);
}

public ActionResult RecipientForm()
{
    var data = new CashRecipient();
    data.cashAmount = "temp";
    data.recipientName = "temp";
    return PartialView(data);
}

Solution

  • First start by creating a view model to represent what you want to edit. I'm assuming cashAmount is a monetary value, so therefore should be a decimal (add other validation and display attributes as required)

    public class CashRecipientVM
    {
        public int? ID { get; set; }
        public decimal Amount { get; set; }
        [Required(ErrorMessage = "Please enter the name of the recipient")]
        public string Recipient { get; set; }  
    }
    

    Then create a partial view (say) _Recipient.cshtml

    @model CashRecipientVM
    <div class="recipient">
        @using (Html.BeginCollectionItem("recipients"))
        {
            @Html.HiddenFor(m => m.ID, new { @class="id" })
            @Html.LabelFor(m => m.Recipient)
            @Html.TextBoxFor(m => m.Recipient)
            @Html.ValidationMesssageFor(m => m.Recipient)
            @Html.LabelFor(m => m.Amount)
            @Html.TextBoxFor(m => m.Amount)
            @Html.ValidationMesssageFor(m => m.Amount)
            <button type="button" class="delete">Delete</button>
        }
    </div>
    

    and a method to return that partial

    public PartialViewResult Recipient()
    {
        return PartialView("_Recipient", new CashRecipientVM());
    }
    

    Then your main GET method will be

    public ActionResult Create()
    {
        List<CashRecipientVM> model = new List<CashRecipientVM>();
        .... // add any existing objects that your editing
        return View(model);
    }
    

    and its view will be

    @model IEnumerable<CashRecipientVM>
    @using (Html.BeginForm())
    {
        <div id="recipients">
            foreach(var recipient in Model)
            {
                @Html.Partial("_Recipient", recipient)
            }
        </div>
        <button id="add" type="button">Add</button>
        <input type="submit" value="Save" />
    }
    

    and will include a script to add the html for a new CashRecipientVM

    var url = '@Url.Action("Recipient")';
    var form = $('form');
    var recipients = $('#recipients');
    $('#add').click(function() {
        $.get(url, function(response) {
            recipients.append(response);
            // Reparse the validator for client side validation
            form.data('validator', null);
            $.validator.unobtrusive.parse(form);
        });
    });
    

    and the script to delete an item

    $('.delete').click(function() {
        var container = $(this).closest('.recipient');
        var id = container.find('.id').val();
        if (id) {
            // make ajax post to delete item
            $.post(yourDeleteUrl, { id: id }, function(result) {
                container.remove();
            }.fail(function (result) {
                // Oops, something went wrong (display error message?)
            }
        } else {
            // It never existed, so just remove the container
            container.remove();
        }
    });
    

    And the form will post back to

    public ActionResult Create(IEnumerable<CashRecipientVM> recipients)