posting JSON to MVC controller - String parameter is null

Question

I am intentionally trying NOT to use a binding in the controller parameter, so I have a controller that looks like:

 [HttpPost]
        public ActionResult UntypedForm(String serializedformdata)
        {
        //// ...
        }

When I post serialized JSON form elements to the controller with the below code:

var formelements = $('#form').serializeArray();
$.post(url, formelements, function (data) {

    }, "json").error(function () {
        alert("Error posting to " + url); 
    });

I get a NULL value for String serializedformdata on my controller. However, when I replace String serializedformdata with a strongly-typed object, binding works properly as expected.

The whole point of my controller is generic JSON posts, where I will create a BSON document to place into a Mongo database. SO....I intentionally DO NOT want model binding and I want the serialized string as pamameter. Why is my serializedformdata string null when I post?

Note - I also tried to bind to Dictionary with

public ActionResult UntypedForm(Dictionary<string,string> serializedformdata)
            {
            //// ...
            }

but serializedformdata is still null.

McGarnagle · Accepted Answer · 2012-09-22 02:15:40Z

2

The function serializeArray creates a Javascript object with the form's key/value pairs. You don't want that, you want a single key/value with serializedformdata = (JSON string). Ie, like this;

var formelements = { serializedformdata: JSON.stringify($('#form').serializeArray()) };

This passes the raw JSON string to the controller's parameter. You can use the JavaScriptSerializer to get the object on the server:

var obj = (List<Dictionary<string,string>>)new JavaScriptSerializer().Deserialize(serializedformdata, typeof(List<Dictionary<string,string>>));
Dictionary<string,string> dict = obj.First();
string someval = dict["somekey"];

edited Sep 22, 2012 at 2:15

answered Sep 22, 2012 at 2:03

McGarnagle

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5 Comments

goldfinger Over a year ago

But doesn't post with "json" argument perform its own stringification? I see your point and agree that serializeArray creates a JS object, but surely that object is serialized by post?

McGarnagle Over a year ago

@goldfinger yes, it's serialized by post, but it's not serialized in the way you want. The JSON keys have to match up with the Action's parameters. So, you could flip my approach and change your action's parameters to the name attributes in your form, and that should also work.

goldfinger Over a year ago

I was a little surprised to see that I need to match the exact name 'serializedformdata' on client stringification and controller parameter name. Apparently controller isn't just generically binding a string but does a literal match on key 'serializedformdata'?

McGarnagle Over a year ago

@goldfinger right, it matches the key. It's a big part of mvc that ties into routing and model binding.

OutOFTouch Over a year ago

Does any got an example like this for dotnet 3.5?

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