ASP.NET MVC 5 ModelState.IsValid with json input code

Question

I have an ASP.NET MVC 5 application with a Test class in my model and a ModelTest function in my controller.

I would like to be able to use ModelState.IsValid when I call the action using AJAX, so passing a JSON object. I tried this

public JsonResult Modeltest(Test input) {
    if (ModelState.IsValid) {
        return Json(new { Response = "Success" }, JsonRequestBehavior.AllowGet);
    }

    return Json(new { Response = "Error" }, JsonRequestBehavior.AllowGet);
}

The Test class is pretty straightforward

public class Test {
    public int num { get; set; }
    public string name { get; set; }
}

And the call will be something like this http://myServer/myController/ModelTest?input={"num":5, "name ":"myName"}

Of course it doesn't works and if I put a breakpoint at the first line in the server the input object is NULL. Is no only possible solution pass a JSON string, deserializing it and manually fill a model object? Isn't there a faster (and automated) way to parse the input as the specified class?

You should be doing this instead: http://myServer/myController/ModelTest?num=5&name=myName show your ajax call aswell — Ric
– Ric, Commented Oct 8, 2015 at 12:45
If you POSTed your JSON then it would work. Not from within the query string like that though — Luke
– Luke, Commented Oct 8, 2015 at 12:46

David · Accepted Answer · 2015-10-08 12:46:47Z

3

This:

http://myServer/myController/ModelTest?input={"num":5, "name ":"myName"}

Is a very invalid URL. Query strings are great for simple key/value pairs, for example:

http://myServer/myController/ModelTest?num=5&name=myName

In fact, for a simple object like your Test class, the model binder should be smart enough to interpret these values into an instance of that object. (I'll be very surprised if it doesn't.)

However, if you have a JSON structure (which you may need for more complex objects) then that structure would have to go in the POST body rather than in the query string.

answered Oct 8, 2015 at 12:46

David

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3 Comments

Luke Over a year ago

In answer to your question, yes MVC is smart enough to bind the query string values to the model like you have stated

Naigel Over a year ago

Thank you! Another question, shouldn't POST be used to insert things and GET to get things? What if I need to pass a complex serialized object from client but just to request content and not to insert?

David Over a year ago

@Naigel: Generally, yes. GET is strictly for observing state and not for changing it. There are semantic arguments to be made for POST, though. And the W3C spec leaves room for interpretation (intentionally). A significant difference between the two is that GET has no request body. So if you need to have a request body, POST is going to be your option. POST is generally for creating resources. But there's room for interpretation with operations like complex searches. If it helps, semantically think of it as "creating a set of search results".

Luke · Accepted Answer · 2015-10-08 12:49:02Z

1

If you POST your values using AJAX or using a form, it will automatically bind your JSON values to your incoming model in your action method.

Here's an example of jQuery code that you could use to post your JSON:

$.post("http://myServer/myController/ModelTest", {"num":5, "name ":"myName"}, function(e) {

    // Success
});

answered Oct 8, 2015 at 12:49

Luke

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