Getting a "No parameterless constructor defined" error, not sure why

Question

For some reason one particular AJAX call of mine is getting a "No parameterless constructor defined" error. Here's the code:

CallAndReplace(JSON.stringify(model), url, $("#panel"));

function CallAndReplace(data, url, replace) {
    $.ajax({
        url: url,
        type: "post",
        contentType: "application/json; charset=utf-8",
        data: data,
        success: function (result) {
            replace.html(result);
        },
        error: function (x, e) {
            if (x.status == 0) {
                alert('You are offline!!\n Please Check Your Network.');
            } else if (x.status == 404) {
                alert('Requested URL not found.');
            } else if (x.status == 500) {
                alert('Internal Server Error.');
            } else if (e == 'parsererror') {
                alert('Error.\nParsing JSON Request failed.');
            } else if (e == 'timeout') {
                alert('Request Time out.');
            } else {
                alert('Unknow Error.\n' + x.responseText);
            }
        }
    });
}

'model' is a viewmodel in my MVC-3 view that I've converted into a Javascript object. 'url' is the url generated via the '@Url.Action("Action", "Controller")' method. And $("#panel") is the div area that gets replaced by a partial view returned by the controller action.

When I try to debug the project, it never gets to the controller action. When I created a dummy controller action with no parameters, it reaches there in debug mode. But I'm obviously sending data. I can see the data being posted in Firebug (although it's not structured for some reason) but apparently it's not being sent over and I don't know why.

I use CallAndReplace 20 other times in my code for other uses and it has never given me this problem. I am completely at a loss as to why.

Edit: Here's the viewmodel class that I'm sending to the view:

public class AwardsEdit
{
    public List<AwardsViewModel> Awards { get; set; }
    public int TitleId { get; set; }

    public List<Tuple<int, string>> Participants { get; set; }
    public List<Award1> AllAwards { get; set; }
    public List<Tuple<int, string>> AllAwardCompanies { get; set; }
}

And the controller action I'm trying to call:

public PartialViewResult SaveAwards(AwardsEdit award)
    {
        if (ModelState.IsValid)
        {
            bool updated = _translator.UpdateAward(award);
            if (updated)
            {
                return PartialView("Details", _translator.GetAwards(award.TitleId));
            }
            //else error
            ModelState.AddModelError("", "Award data was not saved.");
        }
        //on error, load meta data
        var data = _translator.GetAwards(award.TitleId, true);

        award.Participants = data.Participants;
        award.AllAwards = data.AllAwards;
        award.AllAwardCompanies = data.AllAwardCompanies;

        return ViewAwards(award.TitleId);
    }

The controller itself doesn't have a parameterless constructor method and I am using dependency injection, but I have other AJAX calls that call various actions in that controller and they work fine. I don't know why this one isn't working.

Can you post your controller code? Are you doing any dependency injection? I get this error when my controller does not have a default parameterless constructor. — danludwig
– danludwig, Commented Dec 13, 2011 at 21:29
that error is server side, check to see if your data contains anything before you make the Ajax call, sounds like dependency on your controller is not working for that call — Kris Ivanov
– Kris Ivanov, Commented Dec 13, 2011 at 21:30
Please post the code for the action in your controller that accepts your AJAX as well as the constructor(s) for the model it accepts. I suspect that you are accepting a Model/ViewModel of some type and your Model/ViewModel doesn't have a constructor that takes 0 arguments. When the ModelBinder in .NET tries to convert the incoming form to your model type it requires that your model have a constructor that takes 0 parameters. — Nick Bork
– Nick Bork, Commented Dec 13, 2011 at 21:33
You answered your own question: "The controller itself doesn't have a parameterless constructor method and I am using dependency injection". You'll need to dig in to the dependency injection to figure out why that isn't working. — Nick Bork
– Nick Bork, Commented Dec 13, 2011 at 21:50

Scott Rippey · Accepted Answer · 2011-12-14 01:36:01Z

11

The error is probably referring to the type of one of your action's parameters (not the Controller, as others have suggested).
MVC cannot populate the parameter if it cannot first be constructed.

For example, you can get the same error like this:

public class ParameterConstructor
{
    public ParameterConstructor(string parameter){
    }
}

public class MyController : Controller {
    public ActionResult Test(ParameterConstructor model) {
        return "This action will not be reached";
    }
}

So you need to make sure that your model type has a parameterless constructor.

Update

In response to your updated code, it is true that your ViewModel constructor is parameterless.
However, you have a list of Tuple<int, string>. The documentation says that Tuple does not have a parameterless constructor. That's the problem -- Tuple is designed to be read-only. Perhaps you could use a KeyValuePair<> instead?

edited Dec 14, 2011 at 1:36

answered Dec 13, 2011 at 21:31

Scott Rippey

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4 Comments

Jay Sun Over a year ago

My other view models don't have parameterless constructors and sending them through AJAX works fine.

Scott Rippey Over a year ago

@JaySun Interesting ... if the constructor isn't parameterless, then what parameters does MVC call it with? Can you set a breakpoint inside the constructor and see what values you get? I'm genuinely curious.

Scott Rippey Over a year ago

@JaySun It looks like Tuple<> does not have a parameterless constructor. That's probably the problem. I updated my answer accordingly.

Ian Over a year ago

Perfect thanks. I had SelectList, which didn't have a parameterless constructor so had to use IEnumerable<SelectListItem>

Pointy · Accepted Answer · 2011-12-13 21:29:52Z

0

If you want to pass JSON to your server, you have to pass it as the value of a parameter. Just setting the "data" property on the AJAX call won't work.

You could use:

    data: { theJson: data },

then your server would see a parameter "theJSON" and could decode the value of that to get your data structure back.

answered Dec 13, 2011 at 21:29

Pointy

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Comments

Travis J · Accepted Answer · 2011-12-13 21:29:57Z

0

.stringify is the reason it is not structured. That call will take your data, add a [ to the front, a ] to the back, and then create a comma delineated string of the data you sent. Perhaps your controller expects an object or model and is instead getting a string.

answered Dec 13, 2011 at 21:29

Travis J

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Comments

Phil Klein · Accepted Answer · 2011-12-13 21:30:17Z

0

I would verify that the Controller referenced in your @Url.Action("Action", "Controller") actually has a parameterless constructor. Or it could be that you do not expect there to be an parameterless constructor in which case you must make sure that your IoC Container is properly configured to inject the necessary dependency.

It could also be the ViewModel itself in which case you should ensure that a parameterless (default) constructor exists on the ViewModel type.

Example:

public class Example
{
    // this is a parameterless constructor
    public Example()
    {
        // ...
    }
}

answered Dec 13, 2011 at 21:30

Phil Klein

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danludwig · Accepted Answer · 2011-12-13 21:30:24Z

0

public class MyController : Controller
{
    // make sure constructor has default parameterless constructor
    public MyController() {}
}

answered Dec 13, 2011 at 21:30

danludwig

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Comments

Wyatt Barnett · Accepted Answer · 2011-12-13 21:31:12Z

0

That error message isn't the greatest -- it sends people to one of the more likely causes of your controller class not being instantiated. But it really should read "Controller construction and initialization failed. One likey cause is that there is not a parameterless constructor but you might have screwed it up some other way. Inner exception was . . ."

Best bet to catch it would be to run your code in debug mode, Visual Studio should pop you over to the exception when it occurs.

answered Dec 13, 2011 at 21:31

Wyatt Barnett

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2 Comments

Jay Sun Over a year ago

I did run my code in debug mode. Nothing happened. The error just appeared in my browser.

Wyatt Barnett Over a year ago

Interesting. Did you look at the debug window, sometimes that will let you know. Requesting the AJAX url directly could help too, as will inspecting the result -- it might have the inner exception which is what you need to get at.

Nick Bork · Accepted Answer · 2011-12-13 21:51:33Z

0

Since you're using Dependency Injection you'll need to dig in to your code to figure out why the dependency injector isn't creating an instance of the controller with the paramteres it requires.

edited Dec 13, 2011 at 21:51

answered Dec 13, 2011 at 21:36

Nick Bork

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