响应JSON格式根据成功/错误而变化：为什么？

Question

I'm building a Web Api, using an Ajax call to test an action for uploading files.

The Ajax looks just like this:

$.ajax({
    type: 'POST',
    cache: false,
    contentType: false,
    processData: false,
    url: './Customer/' + self.uploadCustomer() + '/Upload',
    data: formData,
    headers: headers,
    success: function (result) {
        self.result(JSON.stringify(result));
    },
    error: function (result) {
        self.result(JSON.stringify(result));
    }
});

In my action, I want to return a JSON custom object if there's an error, such as:

return ResponseMessage(Request.CreateResponse(HttpStatusCode.OK, new ResultError(ErrorCode.CustomerNotFound)));

which returns exactly the following, as it should

{
    "Errors": [
        {
            "Message": "Customer doesn't exist or access is forbidden.",
            "Code": 201
        }
    ]
}

But if instead of using HttpStatusCode.OK I use any other, such as HttpStatusCode.NotFound in exactly the same call that I have above:

return ResponseMessage(Request.CreateResponse(HttpStatusCode.NotFound, new ResultError(ErrorCode.CustomerNotFound)));

I get this result instead:

{
    "readyState":4,
    "responseText":"{\"Errors\":[{\"Message\":\"Customer doesn't exist or access is forbidden.\",\"Code\":201}]}",
    "responseJSON":{"Errors":[{"Message":"Customer doesn't exist or access is forbidden.","Code":201}]},
    "status":404,
    "statusText":"Not Found"
}

Why? And how do I get rid of it?

Answer 1

You should use result.responseText or result.responseJSON according to your response content type. Because the 'result' is just response body for success event but response body + other response related properties for the error state.

PS: $.ajax's success event only satisfies with HTTP/200 results and for the other reponse codes, it causes the error event fire.