Rendering partial view in ASP.Net MVC3 Razor using

Question

The base functionality I wish to achive is that the contents of a table are updated when a dropdownlist item is selected. This will update when the user makes a new selection and retrieve new information from the database and repopulate the table.

It's also worth noting that the DropDownListFor that I want the .change() to work with is not contained within the AjaxForm but appears elsewhere on the page (admittedly in another form)

To achieve this I looked at this question: Rendering partial view dynamically in ASP.Net MVC3 Razor using Ajax call to Action which does a good job of going part the way of what I want to do.

So far, I have a controller method which handles populating a customized viewmodel for the partial view:

    [HttpPost]
    public ActionResult CompanyBillingBandDetails(int id = 0)
    {
        var viewModel = new BillingGroupDetailsViewModel();
        var billingGroupBillingBands =
            _model.GetAllRecordsWhere<BillingGroupBillingBand>(x => x.BillingGroupId == id).ToList();

        foreach (var band in billingGroupBillingBands)
        {
            viewModel.BillingBands.Add(band.BillingBand);
        }

        return PartialView("BillingGroupDetailsPartial", viewModel);
    }

The ViewModel I wish to populate each call:

 public class BillingGroupDetailsViewModel
    {
        public List<BillingBand> BillingBands { get; set; }
    }

The strongly typed model I'm using as a model for the partial view

public class BillingBandsObject
    {
        public int BillingBandId { get; set; }
        public int RangeFrom { get; set; }
        public int RangeTo { get; set; }
        public Decimal Charge { get; set; }
        public int BillingTypeId { get; set; }
        public bool Delete { get; set; }
    }

The partial view it populates and returns:

@model xxx.xxx.DTO.Objects.BillingBandsObject


<tr>
    <td>
        @Html.DisplayTextFor(x => x.RangeFrom)
    </td>
</tr>
<tr>
    <td>
        @Html.DisplayTextFor(x => x.RangeTo)
    </td>
</tr>
<tr>
    <td>
        @Html.DisplayTextFor(x => x.Charge)
    </td>
</tr>

The Razor code for this section of the page:

    <table>
        <thead>
           <tr>
               <th>
                  Range From
               </th>
               <th>
                  Range To
               </th>
               <th>
                  Charge
               </th>
           </tr>
        </thead>
    <tbody>

    @using (Ajax.BeginForm("CompanyBillingBandDetails", new AjaxOptions() { UpdateTargetId = "details", id = "ajaxform" }))
    {
    <div id="details">
        @Html.Action("CompanyBillingBandDetails", new { id = 1 })
    </div>
    }

    </tbody>
 </table>

and finally the function I lifted almost straight from Darin's answer:

$(function () {
        $('#billinggrouplist').change(function () {
            // This event will be triggered when the dropdown list selection changes

            // We start by fetching the form element. Note that if you have
            // multiple forms on the page it would be better to provide it
            // an unique id in the Ajax.BeginForm helper and then use id selector:
            var form = $('#ajaxform');

            // finally we send the AJAX request:
            $.ajax({
                url: form.attr('action'),
                type: form.attr('method'),
                data: form.serialize(),
                success: function (result) {
                    // The AJAX request succeeded and the result variable
                    // will contain the partial HTML returned by the action
                    // we inject it into the div:
                    $('#details').html(result);
                }
            });
        });
    });

At the moment I have fought through a number of errors, currently I am faced with :

"Error executing child request for handler 'System.Web.Mvc.HttpHandlerUtil+ServerExecuteHttpHandlerAsyncWrapper'."

However, i feel my understanding of the problem as a whole may be lacking.

Any help appreciated!

Answer 1

This error means that there was an exception while rendering your child view. Probably something related to your data, ie. NulLReferenceException.

Just attach your debugger and set to to break when an exception is thrown.