Question

I am trying to create what I feel is a very simple form submission using a ViewModel. I have worked on this off and on all day and for some reason cannot understand why when my app gets to my HttpPost action my EmailViewModel is empty. I get a “NullReference Exception Occurred” “Object reference not set to an instance of an object” error.

Can you take a look at my code and tell me where I am being crazy?

Here is my httpPost action:

[HttpPost]
public ActionResult SendStudentAnEmail(EmailViewModel email)
{
        Debug.Write(email.Subject); // First NullReferenceException
        Debug.Write(email.Body);
        Debug.Write(email.Email);
        etc. . .

My ViewModel:

namespace MyApp.ViewModels
{
    public class EmailViewModel
    {
        public string Email { get; set; }

        public string Subject { get; set; }

        public string Body { get; set; }
    }
}

and My View:

@model MyApp.ViewModels.EmailViewModel

@{
    ViewBag.Title = "SendStudentAnEmail";
}

<h2>SendStudentAnEmail</h2>

<script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script>

@using (Html.BeginForm()) {
    @Html.ValidationSummary(true)
    <fieldset>
        <legend>EmailViewModel</legend>

        <div class="editor-label">
            @Html.LabelFor(model => model.Email)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Email)
            @Html.ValidationMessageFor(model => model.Email)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.Subject)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Subject)
            @Html.ValidationMessageFor(model => model.Subject)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.Body)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.Body)
            @Html.ValidationMessageFor(model => model.Body)
        </div>

        <p>
            <input type="submit" value="Save" />
        </p>
    </fieldset>
}

<div>
    @Html.ActionLink("Back to List", "Index")
</div>

Thank you.

*UPDATE*

If I change my HttpPost Action to use FormCollection, I can use the values just fine, I can even re-cast the FormCollection values back to my EmailViewModel. Why is this?

[HttpPost]
public ActionResult SendStudentAnEmail(FormCollection emailFormCollection)
{
        Debug.Write(emailFormCollection["email"]);
        Debug.Write(emailFormCollection["subject"]);
        Debug.Write(emailFormCollection["body"]);
    var email = new EmailViewModel
                        {
                            Email = emailFormCollection["email"],
                            Subject = emailFormCollection["subject"],
                            Body = emailFormCollection["body"]
                        };
. . . . then the rest of my code works just how I wanted. . . 

Why do I have to cast from FormCollection over to my EmailViewModel? Why isn’t it giving me the NullReference Exception if I attempt to simply push an EmailViewModel into my Action?

Answer 1

Your EmailViewModel class has a property called Email of type string. And your controller action takes an argument called email of type EmailViewModel. This confuses the default model binder. So either rename the property inside the view model or the action argument:

[HttpPost]
public ActionResult SendStudentAnEmail(EmailViewModel model)
{
    Debug.Write(model.Subject);
    Debug.Write(model.Body);
    Debug.Write(model.Email);
    ...
}