Browser prompting download of JSON response, ASP.NET MVC2

Question

I've encountered this problem all of a sudden doing a simple ajax submit of a form. The JSON comes back formatted correctly but the browser prompts to download it. Fiddler shows the content-type as correct:

application/json; charset: utf-8

Here's my javascript:

 $("#submitbutton").click(function(e) {
 $.post('FormTest', function(o) {
  FormCallback(o);
  });
}); 

Here is the server side:

public JsonResult FormTest(string test) {
        return Json("This worked!");
    }

Again, I get back an object from the server fine, but it either prompts me to download (Firefox) or simply shows the object in a new tab in the browser (Chrome).

I found one other question like this but the author didn't explain what was wrong. This is crazy! Any ideas?

Edit: The correct code is below, beside the e.preventDefault, I also needed to tell it which form data to use:

  $("#submit-button").click(function(e) {
    $.post('address', $("#form").serialize(), function(o) {
        FormCallback(o);
    });
   e.preventDefault();
});

Answer 1

You want to cancel the default action, I expect:

 $("#submitbutton").click(function(e) {
 $.post('FormTest', function(o) {
  FormCallback(o);
  });
  return false; // <<=====
});

You can also try:

e.preventDefault();

if that doesn't work by itself

Answer 2

In addition to @Marc's answer I would like to add that:

return Json("This worked!");

in fact doesn't work as it doesn't return a valid JSON object. It simply returns "This worked!" to the client. You need to construct the object:

return Json(new { Message = "This worked!" });

Answer 3

MVC 2 returns JSON mimetype by default. If you want to receive JSON data in plain HTML you should pass your JSON data as following:

return Json(model, "text/html", JsonRequestBehavior.AllowGet);

Another point, you can mark your Action with [ChildActionOnly] and call your action in your view this way

var json = <%= Html.Action("YourActionMethod", "YourControllerName") %>