ASP.NET MVC How to pass JSON object from View to C

Question

I have a complex JSON object which is sent to the View without any issues (as shown below) but I cannot work out how Serialize this data back to a .NET object when it is passed back to the controller through an AJAX call. Details of the various parts are below.

   var ObjectA = {
        "Name": 1,
        "Starting": new Date(1221644506800),

        "Timeline": [
            {
                "StartTime": new Date(1221644506800),
                "GoesFor": 200

            }
            ,
            {
                "StartTime": new Date(1221644506800),
                "GoesFor": 100

            }

        ]
    };

I am not sure how this object can be passed to a Controller Method, I have this method below where the Timelines object mirrors the above JS object using Properties.

public JsonResult Save(Timelines person)

The jQuery I am using is:

        var encoded = $.toJSON(SessionSchedule);

        $.ajax({
            url: "/Timeline/Save",
            type: "POST",
            dataType: 'json',
            data: encoded,
            contentType: "application/json; charset=utf-8",
            beforeSend: function() { $("#saveStatus").html("Saving").show(); },
            success: function(result) {
                alert(result.Result);
                $("#saveStatus").html(result.Result).show();
            }
        });

I have seen this question which is similar, but not quite the same as I am not using a forms to manipulate the data. How to pass complex type using json to ASP.NET MVC controller

I have also seen references to using a 'JsonFilter' to manually deserialize the JSON, but was wondering if there is a way to do it nativly though ASP.NET MVC? Or what are the best practices for passing data in this way?

Answer 1

Edit:

This method should no longer be needed with the arrival of MVC 3, as it will be handled automatically - http://weblogs.asp.net/scottgu/archive/2010/07/27/introducing-asp-net-mvc-3-preview-1.aspx

---

You can use this ObjectFilter:

    public class ObjectFilter : ActionFilterAttribute {

    public string Param { get; set; }
    public Type RootType { get; set; }

    public override void OnActionExecuting(ActionExecutingContext filterContext) {
        if ((filterContext.HttpContext.Request.ContentType ?? string.Empty).Contains("application/json")) {
            object o =
            new DataContractJsonSerializer(RootType).ReadObject(filterContext.HttpContext.Request.InputStream);
            filterContext.ActionParameters[Param] = o;
        }

    }
}

You can then apply it to your controller methods like so:

    [ObjectFilter(Param = "postdata", RootType = typeof(ObjectToSerializeTo))]
    public JsonResult ControllerMethod(ObjectToSerializeTo postdata) { ... }

So basically, if the content type of the post is "application/json" this will spring into action and will map the values to the object of type you specify.

Answer 2

A different take with a simple jQuery plugin

Even though answers to this question are long overdue, but I'm still posting a nice solution that I came with some time ago and makes it really simple to send complex JSON to Asp.net MVC controller actions so they are model bound to whatever strong type parameters.

This plugin supports dates just as well, so they get converted to their DateTime counterpart without a problem.

You can find all the details in my blog post where I examine the problem and provide code necessary to accomplish this.

All you have to do is to use this plugin on the client side. An Ajax request would look like this:

$.ajax({
    type: "POST",
    url: "SomeURL",
    data: $.toDictionary(yourComplexJSONobject),
    success: function() { ... },
    error: function() { ... }
});

But this is just part of the whole problem. Now we are able to post complex JSON back to server, but since it will be model bound to a complex type that may have validation attributes on properties things may fail at that point. I've got a solution for it as well. My solution takes advantage of jQuery Ajax functionality where results can be successful or erroneous (just as shown in the upper code). So when validation would fail, error function would get called as it's supposed to be.

Answer 3

You say "I am not using a forms to manipulate the data." But you are doing a POST. Therefore, you are, in fact, using a form, even if it's empty.

$.ajax's dataType tells jQuery what type the server will return, not what you are passing. POST can only pass a form. jQuery will convert data to key/value pairs and pass it as a query string. From the docs:

Data to be sent to the server. It is converted to a query string, if not already a string. It's appended to the url for GET-requests. See processData option to prevent this automatic processing. Object must be Key/Value pairs. If value is an Array, jQuery serializes multiple values with same key i.e. {foo:["bar1", "bar2"]} becomes '&foo=bar1&foo=bar2'.

Therefore:

1. You aren't passing JSON to the server. You're passing JSON to jQuery.
2. Model binding happens in the same way it happens in any other case.

Answer 4

This answer is a follow up to DaRKoN_'s answer that utilized the object filter:

[ObjectFilter(Param = "postdata", RootType = typeof(ObjectToSerializeTo))]
    public JsonResult ControllerMethod(ObjectToSerializeTo postdata) { ... }

I was having a problem figuring out how to send multiple parameters to an action method and have one of them be the json object and the other be a plain string. I'm new to MVC and I had just forgotten that I already solved this problem with non-ajaxed views.

What I would do if I needed, say, two different objects on a view. I would create a ViewModel class. So say I needed the person object and the address object, I would do the following:

public class SomeViewModel()
{
     public Person Person { get; set; }
     public Address Address { get; set; }
}

Then I would bind the view to SomeViewModel. You can do the same thing with JSON.

[ObjectFilter(Param = "jsonViewModel", RootType = typeof(JsonViewModel))] // Don't forget to add the object filter class in DaRKoN_'s answer.
public JsonResult doJsonStuff(JsonViewModel jsonViewModel)
{
     Person p = jsonViewModel.Person;
     Address a = jsonViewModel.Address;
     // Do stuff
     jsonViewModel.Person = p;
     jsonViewModel.Address = a;
     return Json(jsonViewModel);
}

Then in the view you can use a simple call with JQuery like this:

var json = { 
    Person: { Name: "John Doe", Sex: "Male", Age: 23 }, 
    Address: { Street: "123 fk st.", City: "Redmond", State: "Washington" }
};

$.ajax({
     url: 'home/doJsonStuff',
     type: 'POST',
     contentType: 'application/json',
     dataType: 'json',
     data: JSON.stringify(json), //You'll need to reference json2.js
     success: function (response)
     {
          var person = response.Person;
          var address = response.Address;
     }
});

Answer 5

There is the JavaScriptSerializer class you can use too. That will let you deserialize the json to a .NET object. There's a generic Deserialize<T>, though you will need the .NET object to have a similar signature as the javascript one. Additionally there is also a DeserializeObject method that just makes a plain object. You can then use reflection to get at the properties you need.

If your controller takes a FormCollection, and you didn't add anything else to the data the json should be in form[0]:

public ActionResult Save(FormCollection forms) {
  string json = forms[0];
  // do your thing here.
}

Answer 6

in response to Dan's comment above:

I am using this method to implement the same thing, but for some reason I am getting an exception on the ReadObject method: "Expecting element 'root' from namespace ''.. Encountered 'None' with name '', namespace ''." Any ideas why? – Dan Appleyard Apr 6 '10 at 17:57

I had the same problem (MVC 3 build 3.0.11209.0), and the post below solved it for me. Basically the json serializer is trying to read a stream which is not at the beginning, so repositioning the stream to 0 'fixed' it...

http://nali.org/asp-net-mvc-expecting-element-root-from-namespace-encountered-none-with-name-namespace/