Question

I have a complex object that I want to use in an edit view. To simplify things I have created a ViewModel and have successfully created the edit view page, and everything renders correctly. When I hit save, everything falls apart.

The ViewModel is as follows:

public class ClosureEditViewModel
{

    public Model.Closure Closure { get; set; }
    public Model.School School { get; set; }
    public Model.ClosureDetail CurrentDetails { get; set; }
}

Some of the View is as follows:

<div class="display-label">School</div>
<div class="display-field">
    @Html.DisplayFor(model => model.Closure.School.Name)
</div>
<div class="display-label">Closed</div>
<div class="display-field">
    @Html.DisplayFor(model => model.Closure.Logged)
</div>
....
<div class="editor-label">
    @Html.LabelFor(model => model.CurrentDetails.DateOpening, "Date Opening (dd/mm/yyyy)")
</div>
<div class="editor-field">
    @Html.TextBox("DateOpening", Model.CurrentDetails.DateOpening.ToString("dd/MM/yyyy"))
    @Html.ValidationMessageFor(model => model.CurrentDetails.DateOpening)
</div>
....
    <tr>
        <td>
            @Html.CheckBoxFor(model => model.CurrentDetails.Nursery, (Model.School.Nursery ? null : new { @disabled = "disabled" }))
        </td>

The important parts of the controller are as follows:

    public ActionResult Edit(int id)
    {
        Data.IClosureReasonRepository reasonRepository = new Data.SqlServer.Repositories.ClosureReasonRepository(UnitOfWork);
        IEnumerable<Model.ClosureReason> reasons = reasonRepository.GetAll();

        Model.Closure closure = ClosureRepository.GetClosure(id);
        Model.ClosureDetail currentDetail = closure.ClosureDetails.Last();
        ViewModels.ClosureEditViewModel editClosure = new ViewModels.ClosureEditViewModel() { Closure = closure, School = closure.School, CurrentDetails = closure.ClosureDetails.Last() };
        ViewBag.ReasonId = new SelectList(reasons, "Id", "Name", currentDetail.ReasonId);
        return View(editClosure);
    }

    [HttpPost]
    public ActionResult Edit(ViewModels.ClosureEditViewModel newDetail)
    {
        //if (ModelState.IsValid)
        //{

        //}

        Data.IClosureReasonRepository reasonRepository = new Data.SqlServer.Repositories.ClosureReasonRepository(UnitOfWork);
        IEnumerable<Model.ClosureReason> reasons = reasonRepository.GetAll();
        ViewBag.ReasonId = new SelectList(reasons, "Id", "Name", newDetail.CurrentDetails.ReasonId);
        return View(newDetail);
    }

When I hit save the following message appears:

Object reference not set to an instance of an object.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error: 


Line 94:                 </td>
Line 95:                 <td>
Line 96:                     @Html.CheckBoxFor(model => model.CurrentDetails.P1, (Model.School.P1 ? null : new { @disabled = "disabled" }))
Line 97:                 </td>
Line 98:                 <td>

I just can’t figure out why it is having problems with the School property but neither of the other two.

James 🙂

Answer 1

It seems that Model.School is null when you render the view once again in the POST action. Make sure that it isn’t null because in your view you don’t have a single input field bound to the School property => this property will be null inside your POST controller action.

[HttpPost]
public ActionResult Edit(ClosureEditViewModel viewModel)
{
    ... some operations

    // Make sure that viewModel.School is not null
    // Remember that the checkbox is bound to CurrentDetails.P1 so 
    // when you post to this action there is nothing that will initialize
    // the School property => you should do whatever you did in your GET
    // action in order to initialize this property before returning the view
    return View(viewModel);
}