Question

I am having trouble with the following error message:

Object reference not set to an instance of an object.

break on lines:

Line 16:         </div>
Line 17:         <div class="editor-field">
Line 18:              @Html.DropDownList("KPI.CSF.FYID", Model.Financial_Years)
Line 19:             @Html.ValidationMessageFor(model => model.KPI.CSF.FYID)
Line 20:         </div>

This occurs during form post in my mvc project.

I am passing a viewmodel of the following when I load the create form:

public class KPICreateFormViewModel
    {

        //Properties
        public KPI KPI { get; set; }
        public SelectList Financial_Years { get; private set; }

        FYRepository fyrepo = new FYRepository();
      public KPICreateFormViewModel(KPI kpi)
        {
            KPI = kpi;
            Financial_Years = new SelectList(fyrepo.GetFys(), "ID", "Financial_Year");

        }

    }

I use the financial years for a dropdown which then initiates some ajax to cascade some other dropdowns which will populate ID numbers in my post.

I do not want my financial years dropdown to post anything back during the http post method of my controller.. so I figured if I just pass back the following I would be ok:

[HttpPost]
    public ActionResult Create(KPI kpi)
    {
        try
        {

            kpirepository.Add(kpi);
            kpirepository.Save();


            return RedirectToAction("Details", new { id = kpi.ID });
        }
        catch
        {
            return View();
        }
    }

I assume this is all happening because of my view being based on the viewmodel and then on post I am not handing this back? After hours of messing with the cascade code to get it working my head is a bit fried to try and tackle this issue.. help!

The relevant part for my view showing the financial year dropdown:

@model ES_Business_Intelligence.ViewModels.Admin.KPICreateFormViewModel

@using (Html.BeginForm()) {
    @Html.ValidationSummary(true)

    <fieldset>
        <legend>KPI</legend>
        <div class="editor-label">
            @Html.LabelFor(model => model.KPI.CSF.FYID)
        </div>
        <div class="editor-field">
             @Html.DropDownList("KPI.CSF.FYID", Model.Financial_Years)
            @Html.ValidationMessageFor(model => model.KPI.CSF.FYID)
        </div>

Answer 1

After confirmation of the problem from webdeveloper I did some more digging and found I can tell certain elements of my viewmodel to not bind when returning data from my form submit. I added the following code to my viewmodel:

[Bind(Exclude = "Financial_Years")]
    public class KPICreateFormViewModel
    {

        //Properties
        public KPI KPI { get; set; }
        public SelectList Financial_Years { get; private set; }

        FYRepository fyrepo = new FYRepository();
      public KPICreateFormViewModel(KPI kpi)
        {
            KPI = kpi;
            Financial_Years = new SelectList(fyrepo.GetFys(), "ID", "Financial_Year");

        }

    }

The magic is all in the first line:

[Bind(Exclude = "Financial_Years")]