Question

Good evening everyone. I am currently using MVC 3 and I have a viewmodel that contains a property that is a List. I am currently using json2’s JSON.stringify method to pass my viewmodel to my action method. While debugging I am noticing that all the simple properties are coming thru but the collection property is empty even though I know for sure that there is at least one object in the collection. I wanted to know if there is anyone that is running into the same issue. Below is the code that I am using to post to the action method:

$.post("/ReservationWizard/AddVehicleToReservation/",
        JSON.stringify('@ViewData["modelAsJSON"]'),
        function (data) {
            if (data != null) {
                $("#vehicle-selection-container").html(data);
                $(".reservation-wizard-step").fadeIn();
            }
        });

The object @ViewData["modelAsJSON"] contains the following json and is passed to my action method
{"NumberOfVehicles":1,"VehiclesToService":[{"VehicleMakeId":0,"VehicleModelId":0}]}

As you can see the property “VehiclesToService” has one object but when it gets to my action method it is not translated to the corresponding object in the collection, but rather the collection is empty.

If anyone has any insight into this issue it would be greatly appreciated.

Thanks in advance.

UPDATE

OK after making the recommended changes and making the call to new JavaScriptSerializer().Serialize(@Model) this is the string that ultimately gets sent to my action method through the post
'{"NumberOfVehicles":1,"VehiclesToService":[{"VehicleMakeId":0,"VehicleModelId":0}]}'

I can debug and see the object that gets sent to my action method, but again the collection property is empty and I know that for sure there is at least one object in the collection.

The AddVehicleToReservation action method is declared as follows:
public ActionResult AddVehicleToReservation(VehicleSelection selections)
{
...
return PartialView("viewName", model);
}

Answer 1

Here’s the problem:

JSON.stringify('@ViewData["modelAsJSON"]')

JSON.stringify is a client side function and you are passing as argument a list that’s stored in the ViewData so I suppose that it ends up calling the .ToString() and you have

JSON.stringify('System.Collections.Generic.List<Foo>')

in your final HTML which obviously doesn’t make much sense. Also don’t forget that in order to pass parameters to the server using the $.post function the second parameter needs to be a javascript object which is not what JSON.stringify does (it generates a string). So you need to end up with HTML like this:

$.post(
    'ReservationWizard/AddVehicleToReservation',
    [ { id: 1, title: 'title 1' }, { id: 2, title: 'title 2' } ],
    function (data) {
        if (data != null) {
            $('#vehicle-selection-container').html(data);
            $('.reservation-wizard-step').fadeIn();
        }
    }
);

So to make this work you will first need to serialize this ViewData into JSON. You could use the JavaScriptSerializer class for this:

@{
    var myList = new JavaScriptSerializer().Serialize(ViewData["modelAsJSON"]);
}
$.post(
    '@Url.Action("AddVehicleToReservation", "ReservationWizard")',
    // Don't use JSON.stringify: that makes JSON request and without
    // proper content type header your sever won't be able to bind it
    @myList,
    function (data) {
        if (data != null) {
            $('#vehicle-selection-container').html(data);
            $('.reservation-wizard-step').fadeIn();
        }
    }
);

And please don’t use this ViewData. Make your views strongly typed and use view models.