MVC4 AJAX发布JSON

Question

this is my function, where i post json only

function test() {
            var imgFile = document.getElementById('image');
            //            var imgData = JSON.stringify(getBase64Image(imgElem));
            //var imgData = Convert.FormBase64String(imgElem);

            $.ajax({
                type: 'POST',
                dataType: 'json',
                url: "http://localhost:59102/Contacts/AddContact",
                data: "json=" + "{\"token\":\"8mVm/nS1OfpU+nlQLbJjqXJ7kJI=VyLGI2GEKkGgtDt0babrAw==\"}",

                success: function (returnPayload) {
                    console && console.log("request succeeded");
                },
                error: function (xhr, ajaxOptions, thrownError) {
                    console && console.log("request failed");
                },

                processData: false,
                async: false
            });

and i dont know how to add to my data, image, i need to post json and image

this is my controller

[HttpPost]
        [AllowAnonymous]
        public JsonResult AddContact(string json, HttpPostedFileBase file)
        {}