Ajax - 500 Internal Server Error

Question

I am trying to learn AJAX for this project at work. I have a site that loads medications that a patient is taking.

I call this AJAX function up recursively so that i

Answer 1

I had the same error. It turns out that the cause was that the back end method was expecting different json data. In my Ajax call i had something like this:

$.ajax({
        async: false,
        type: "POST",
        url: "http://13.82.13.196/api.aspx/PostAjax",
        data: '{"url":"test"}',
        contentType: "application/json; charset=utf-8",
        dataType: "json",
    });

Now in my WebMethod, inside my C# backend code i had declared my endpoint like this:

public static string PostAjax(AjaxSettings settings)

Where AjaxSettings was declared:

public class AjaxSettings
{
    public string url { get; set; }
}

The problem then was that the mapping between my ajax call and my back-end endpoint was not the same. As soon as i changed my ajax call to the following, it all worked well!

var data ='{"url":"test"}';    
$.ajax({
    async: false,
    type: "POST",
    url: "http://13.82.13.196/api.aspx/PostAjax",
    data: '{"settings":'+data+'}',
    contentType: "application/json; charset=utf-8",
    dataType: "json"
});

I had to change the data variable inside the Ajax call in order to match the method signature exactly.

Answer 2

I fixed an error like this changing the places of the routes in routes.php, for example i had something like this:

Route::resource('Mensajes', 'MensajeriaController');
Route::get('Mensajes/modificar', 'MensajeriaController@modificarEstado');

and then I put it like this:

Route::get('Mensajes/modificar', 'MensajeriaController@modificarEstado');
Route::resource('Mensajes', 'MensajeriaController');

Answer 3

Had the very same problem, then I remembered that for security reasons ASP doesn't expose the entire error or stack trace when accessing your site/service remotely, same as not being able to test a .asmx web service remotely, so I remoted into the sever and monitored my dev tools, and only then did I get the notorious message "Could not load file or assembly 'Newtonsoft.Json, Version=3.5.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed' or one of its dep...".

So log on the server and debug from there.

Answer 4

One must use behavior: JsonRequestBehavior.AllowGet in Post Json Return in C#

Answer 5

Uncomment the following line : [System.Web.Script.Services.ScriptService]

Service will start working fine.

[WebService(Namespace = "http://tempuri.org/")]

 [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]

To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line.

[System.Web.Script.Services.ScriptService]

public class WebService : System.Web.Services.WebService 
{

Answer 6

The 500 (internal server error) means something went wrong on the server's side. It could be several things, but I would start by verifying that the URL and parameters are correct. Also, make sure that whatever handles the request is expecting the request as a GET and not a POST.

One useful way to learn more about what's going on is to use a tool like Fiddler which will let you watch all HTTP requests and responses so you can see exactly what you're sending and the server is responding with.

If you don't have a compelling reason to write your own Ajax code, you would be far better off using a library that handles the Ajax interactions for you. jQuery is one option.