AJAX error in ASP.NET c#

Question

I am very new to Ajax and ASP.NET MVC. I have a function, that returns back to AJAX and I need to handle the error situation. When everything works fine, then the code is okay. My question is how to handle the error part. Here is what I have:

To return success I have:

var data = new { success = false };

return Json(data, JsonRequestBehavior.AllowGet);

And I need to know what to return when there is an exception or error??

This is my query:

function DoMailPDF() {
             $("#submitMail").attr("disabled", true);
             var personid = $("#personid").val();
             var unitid = $("#unitid").val();
             var url = "@(Url.Action("SendEmail", "Report"))";
            $.ajax({
                url: url,
                data: { person: personid , unit:unitid},
                success: function () {                    
               // $('input[name=MailSent]').attr('checked', true);
                $("#submitMail").removeAttr("disabled");
                    alert("Email sent!");
                },
                error: function () {                    
                 alert("Email not sent!");
                }
            });
        }

It never comes to the error function. How do I make it go to the error? Any tips and suggestions are most welcome.

I forgot to mention that if success is true or false it doesn't matter. It goes the same success function. — Tulips
– Tulips, Commented Jun 13, 2012 at 13:48
The error method is called when the STATUS CODE of the RESPONSE is other than 200. check the network tab on your browser — frictionlesspulley
– frictionlesspulley, Commented Jun 13, 2012 at 13:51
You might not understand what success/error mean on the AJAX call. "Success" is when the server returns a HTTP status code of 200. "Error" occures when the server returns a response other than 200. Your .NET code is always going to trigger the success event if the status is 200 even if you set your variable to "false". You need to add code to your "success" event to check the response: success: function (response) { if(response.success){ alert('successful');} else {alert('not successful');}} — Nick Bork
– Nick Bork, Commented Jun 13, 2012 at 13:54
Not exactly right, if for example the status code is 304 (Not Modified) it is not considered an error. — Tallmaris
– Tallmaris, Commented Jun 13, 2012 at 13:54

iappwebdev · Accepted Answer · 2012-06-13 13:50:53Z

5

You can access your json response object by writing:

       $.ajax({
            url: url,
            data: { person: personid , unit:unitid},
            dataType: 'json',
            success: function (response) {                    
                if (response.success == false) {
                    // Error handling
                } else {
                    // Success handling
                }
            },
            error: function () {                    
             alert("Email not sent!");
            }
        });

answered Jun 13, 2012 at 13:50

iappwebdev

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Comments

Tallmaris · Accepted Answer · 2012-06-13 14:12:48Z

As Nick Bork already explained in a comment, the error/success status of a response is determined by the Http status code that is sent down in the header. You can still go the suggested way and inspect the response object and the success property but it is clearly not the proper way when you already have a more powerful and long proven mechanism (the HTTP protocol itself).

.NET will use HTTP 200 (OK) when everything goes according to the code but you can change this behaviour in the Controller by accessing the Reponse object like this, for example:

Response.StatusCode = 500; // or any of the other HTTP "failure" status codes

Any status code in the 4xx or 5xx category will trigger the error() handler specified in the $.ajax(...) call. From there you can of course also inspect the proper status code, the response details and every properties of the XHR object to provide a more meaningful user experience.

HTTP status codes are pretty much set in stone and are not likely to change, that's why they are in my opinion definitely preferrable to a custom made solution...

PS: For a list of HTTP status codes, wikipedia is your friend.

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