JQuery Ajax Post results in 500 Internal Server Error

This is Ajax Request Simple Code To Fetch Data Through Ajax Request

$.ajax({
    type: "POST",
    url: "InlineNotes/Note.ashx",
    data: '{"id":"' + noteid+'"}',
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: function(data) {
        alert(data.d);
    },
    error: function(data){
        alert("fail");
    }
});

I run into the same thing today. As suggested before get Firebug for Firefox, Enable Console and preview POST response. That helped me to find out how stupid the problem was. My action was expecting value of a type int and I was posting string. (ASP.NET MVC2)

I just face this problem today. with this kind of error, you won't get any responses from server, therefore, it's very hard to locate the problem.

But I can tell you "500 internal server error" is error with server not client, you got an error in server side script. Comment out the code closure by closure and try to run it again, you'll soon find out you miss a character somewhere.

Can you post the signature of your method that is supposed to accept this post?

Additionally I get the same error message, possibly for a different reason. My YSOD talked about the dictionary not containing a value for the non-nullable value. The way I got the YSOD information was to put a breakpoint in the $.ajax function that handled an error return as follows:

<script type="text/javascript" language="javascript">
function SubmitAjax(url, message, successFunc, errorFunc) {
    $.ajax({
        type:'POST',
        url:url,
        data:message,
        contentType: 'application/json; charset=utf-8',
        dataType: 'json',
        success:successFunc,
        error:errorFunc
        });

};

Then my errorFunc javascript is like this:

function(request, textStatus, errorThrown) {
        $("#install").text("Error doing auto-installer search, proceed with ticket submission\n"
        +request.statusText); }

Using IE I went to view menu -> script debugger -> break at next statement. Then went to trigger the code that would launch my post. This usually took me somewhere deep inside jQuery's library instead of where I wanted, because the select drop down opening triggered jQuery. So I hit StepOver, then the actual next line also would break, which was where I wanted to be. Then VS goes into client side(dynamic) mode for that page, and I put in a break on the $("#install") line so I could see (using mouse over debugging) what was in request, textStatus, errorThrown. request. In request.ResponseText there was an html message where I saw:

<title>The parameters dictionary contains a null entry for parameter 'appId' of non-nullable type 'System.Int32' for method 'System.Web.Mvc.ContentResult CheckForInstaller(Int32)' in 'HLIT_TicketingMVC.Controllers.TicketController'. An optional parameter must be a reference type, a nullable type, or be declared as an optional parameter.<br>Parameter name: parameters</title>

so check all that, and post your controller method signature in case that's part of the issue

I also faced the same problem. Here are two ways by which I have solved it- 1. If you're using some framework, make sure you are sending a CSRF token with the ajax call as well Here is how the syntax will look like for laravel -

<meta name="_token" content="{{ csrf_token() }}">

In your js file make sure to call this before sending the ajax call

$.ajaxSetup({
            headers: {
                'X_CSRF-TOKEN' : $('meta[name="_token"]').attr('content')
            }
        });

2. Another way to solve it would be to change method from post to get

For me, the error was in php file to which i was sending request. Error was in database connectivity. After fixing the php code, error resolved.

Your code contains dataType: json.

In this case jQuery evaluates the response as JSON and returns a JavaScript object. The JSON data is parsed in a strict manner. Any malformed JSON is rejected and a parse error is thrown. An empty response is also rejected.

The server should return a response of null or {} instead.

I'm late on this, but I was having this issue and what I've learned was that it was an error on my PHP code (in my case the syntax of a select to the db). Usually this error 500 is something to do using syntax - in my experience. In other word: "peopleware" issue! :D

As an addition to the "malformed JSON" answer, if the query you are running returns an object or anything that prevents the data to be serialised, you will get this error. You should always be sure you have JSON and only JSON at the end of your action method or whatever it is you are getting the data from.

Usually your property is not completely right or something wrong with your server processing.

try this headers: { 'X-Requested-With': 'XMLHttpRequest' }, in ajax, set type above the url

In my case the error was related to the way entity framework works. I had a one to many relationship between two tables in my database and when I was bringing data from the table which has the foreign key using ajax post it was also fetching the related foreign key table data because lazyloading was enabled by default. because of that , Json return got confused about the data format and was throwing this error. So I had to use _wfocEntities.Configuration.LazyLoadingEnabled = false; this line before my linq query and it solved my issue.

In my case, i was trying server side processing for datatables. And my action method returns thousands of user record as JSON. The problem was JSON max length. This solved my problem.

return new JsonResult()
        {
            ContentEncoding = Encoding.Default,
            ContentType = "application/json",
            Data = returnData,
            JsonRequestBehavior = JsonRequestBehavior.AllowGet,
            MaxJsonLength = int.MaxValue //this is what,I needed.
        };