Ajax call returns parsererror - asp.net-mvc

Question

I have a Controller with the Action Like This
public ActionResult UpdateCompanyInfo(Parameter parameter)
{
bool result = false;
if(ModelState.IsValid)
{
bla bla bla
}
return Json(result, JsonRequestBehavior.AllowGet);
}
I also have a javascript function:
function blabla(){
$.ajax({
type: 'POST',
url: "What Ever",
async: false,
data: JSON.stringify(jsonObject),
dataType: 'json',
contentType: 'application/json; charset=utf-8',
success: function (succeed) {
if (succeed) {
// Some Code
}
},
error: function () {
//Some Other Code
}
});
}
the javascript function calls properly and it hits Action method with the parameter (No problem yet!).
but when the Action method returns bool object using Json function, it hits the javascript error function response with the following parameters:
readyState 4
responseText "true"
status 200
statusText "parsererror"
jQuery15101815967692459196_1384707824272 was not called
I also tried
return Json(new { result }, JsonRequestBehavior.AllowGet); and
return Json(new {succeed = result }, JsonRequestBehavior.AllowGet); and
return Json(new {succeed = result.ToString() }, JsonRequestBehavior.AllowGet);
but they did not work too.
in addition i have an exactly the same function in another controller which calls another same javascript function but it works properly. I don't know what's wrong with it. am i missing something?
----------- EDIT --------------
I don't know why! but when i remove the dataType: 'json', from the Ajax call, and put return Json(result, JsonRequestBehavior.AllowGet); in action method, it works properly. could someone explain it to my "why?"

Answer 1

Actually it seems there is a bug in jquery 1.5.1 and 1.5.0 (which does not exist in previous versions).
In fact when you use dataType: 'json' it tries to parse json as a script and you should use dataType: 'text/json' instead. see this link.

Answer 2

The data returned from the server might not be of json type. So you can use below two method to overcome.
Option 1:
Use dataType: 'text' as part of ajax request.
Option 2:
Remove the dataType from ajax request as it will try to infer it based on the type of the response.

Answer 3

From your response, In controller, there is no json encoded data, jsonformat looks like, {'responseText':'your text here '}

Answer 4

You are only returning a single value which the JSON parser in JS will not accept. Try this:
public ActionResult UpdateCompanyInfo(Parameter parameter)
{
bool result = false;
if(ModelState.IsValid)
{
bla bla bla
}
return Json(new { success = result }, JsonRequestBehavior.AllowGet);
}
The anonymous object returned by JSON will look like this:
[{ "success": true }]
Which you can then deal with in your success handler, like this:
success: function (data) {
if (data.success) {
// Some Code
}
else {
// Bad things going down
}
},