How to respond with a status code 500 to an ajax jsonp request

Question

I have an application that fires an ajax jsonp request to a C# HttpHandler.

function RequestData() {
var parameters = 'value1=' + value + '&value2=' + value2;
$.ajax({
    type: "GET",
    url: 'https://localhost:44300/checkvalues?' + parameters,
    dataType: "jsonp",
    headers: { "cache-control": "no-cache" },
    success: function (msg) {
        alert('all good')
    },
    error: function (jqXHR, exception) {
        alert(jqXHR.status);
    }
});

And here is some of the server side code.

if (OK)
{
    response.ContentEncoding = System.Text.Encoding.UTF8;
    response.ContentType = "application/javascript";
    response.Write(callback + "({ data: 'allOK' });");
}
else
{
    //error
    response.StatusCode = 500;
    response.SuppressFormsAuthenticationRedirect = true;
    response.StatusDescription = "error";
    response.End();
}

When OK is true, there is no problem. The ajax success function is called as expected. But the minute that I set the response status code to eg 500 to trigger the error section of the ajax request, the server response is never received - nothing happens.

How can I modify my response code to enter the ajax error section?

I can trigger a parse-error by changing the response, but I want to do it with Http Status Codes.

Answer 1

You can detect a JSONp error. I'm not sure why jQuery chooses not to.

Here is a JSONp implementation that doesn't use jQuery. You might need to tinker with it a bit to make it work. For instance I'm not sure how jQuery communicates the callback_name .

function jsonp(success_callback, error_callback) {
    var script, callback_name;
    var parameters = 'value1=' + value + '&value2=' + value2;

    callback_name = "generate random name";

    function after() {
        setTimeout(function () {
            document.getElementsByTagName("head")[0].removeChild(script);
        }, 1);
    }

    script = document.createElement('script');
    window[callback_name] = function (response) {
        after();
        success_callback(response);
    };
    script.type = 'text/javascript';
    script.src = "https://localhost:44300/checkvalues?" + parameters + "&callback=" + callback_name;
    script.async = true;
    script.addEventListener('error', function () {
        after();
        error_callback();
    });
    document.getElementsByTagName("head")[0].appendChild(script);
}

jsonp(function () {
    alert("success");
}, function () {
    alert("failure");
});