HttpPost on ASP.Net MVC3 - "No parameterless constructor defined for this object"

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ASP.NET MVC: No parameterless constructor defined for this object

I'm working on an ASP.NET MVC3 application.

I'm trying to use the [HttpPost] to retrieve information when a user enters it on a form.

Basing what I do off the "default" blank ASP.Net project's Logon scripts, I have the following:

In my controller:

    public ActionResult Ticket(int id)
    {
        Models.Ticket model = new Models.Ticket(id);
        return View("Ticket", model);
    }

    [HttpPost]
    public ActionResult Ticket(int id, MMCR.Models.Ticket model)
    {
        if (id != model.TicketNo)
        {
            return View("Error");
        }
        return View("Ticket", model);
    }

And in the View I have:

@using (Html.BeginForm()) {
    <div>
    <fieldset>
    <legend>View Ticket Details</legend>

    <div class="editor-label">
        @Html.LabelFor(m=>m.Status)    
    </div>
    <div class="editor-field">
        @Html.DropDownListFor(m=>m.Status, Model.Status)
    </div>

    <p>
        <input type="submit" value="Update" />
    </p>

    </fieldset>
    </div>
}

(obviously snipping out repetetive stuff).

However, when I click on the button I get an error:

Exception Details: System.MissingMethodException: No parameterless constructor defined for this object.

Can anyone give some advice on how to resolve this?

Which object is missing the parameterless constructor? If it's one of yours, you can take a stab in the dark and add a parameterless constructor to it. — Robert Harvey, Mar 25 '12 at 18:14
None of the stuff in the Stack Trace is from one of my classes. :( — TZHX, Mar 25 '12 at 18:17

score 18 · Accepted Answer · edited Mar 25 '12 at 18:30

18

Your class MMCR.Models.Ticket needs a parameterless constructor.

When you pass an object of this type through the Post method, MVC will create an instance of the class using a parameterless constructor. It will then map the form fields to that object.

edited Mar 25 '12 at 18:30

Robert Harvey

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answered Mar 25 '12 at 18:22

Jeff Siver

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so any information in the model that's not in the form is lost in the new model? – TZHX Mar 25 '12 at 18:29
2

That is correct. If you have information you want to keep, you should add it to the view through Html.HiddenFor(x=>x.PropertyToKeep). That will insure it is populated when the form posts. – Jeff Siver Mar 25 '12 at 18:30
But... I've got that are just displayed as Labels that aren't being transfered over. :/ – TZHX Mar 25 '12 at 18:37
3

Labels don't get transfered because they aren't considered to be HTML controls. Only HTML controls are included; that's why you have to do a HiddenFor to get a value back if you don't have the property in another control. – Jeff Siver Mar 25 '12 at 20:16

HttpPost on ASP.Net MVC3 - "No parameterless constructor defined for this object"

1 Answers1