IE tries to download JSON in ASP. NET MVC 3

Question

I was trying to return Json from my action and after that IE tried to download it and showed me save dialog. I tested it in Firefox, and there it works fine.

return Json(new { success = false, message = ex.Message }, "application/json");

What is the reason of that behavior and how can I solve that issue?

After that in Javascript part I try this

 if (responseJSON.success == false) {
                        alert(responseJSON.message);
                        cancel();
                    }

But IE doesn't show alert anyway. It brings me save dialog.

I tried to change "application/json" with "text/plain" and save dialog disappeared, but I am not able to see alert yet. What am I missing?

EDIT:

Here is my complect Javascript, I am using Valums qquploader(ex-Ajaxupload) for uploading images

 var uploader = new qq.FileUploader({
                element: document.getElementById("image-upload"),
                action: '/Home/ImageUpload',
                allowedExtensions: ['jpg', 'png', 'gif'],
                sizeLimlit: 2048,onComplete: function (id, fileName, responseJSON) {
                    if (responseJSON.success == false) {
                        alert(responseJSON.message);
                        cancel();
                    }
                    else {
                         alert("success");
                          //some code here
                        }
                     }
                   });

I had tested with alert("success"); in my else part and forwarded json as "text/plain" and after that I saw the alert. But in that time responseJSON.success != false for me. Have you any suggestions about that?

Answer 1

I've solved that with this trick

return Json(new { success = false, message = ex.Message }, "text/html");

And now it works. But can me anyone explain why it works with text/html, and didn't work with application/json and text/plain. First is trying to download JSON and second is returning undefined properties for JSON fields.

Answer 2

This problem occurs when using an upload plugin that uses an iframe to do the upload with IE (tested on 9.0).

IE sets the header Accept: text/html, , application/xhtml+xml, */* and so when you reply with Content-type: application/json, it assumes it's the file (or at least that's the only explanation I could find on the web).

Thus, to circumvent that, you need to set Content-type: text/html or Content-type: text/plain.

I would recommend implementing this using an ActionFilter; instead of manually changing the content type, detect IE and a multipart POST and change the content-type accordingly.

Answer 3

Possibly you are not setting a correct mime type for your json content (for IE try text/plain)

See: What problems may using the MIME type application/json cause?