在浏览器中下载Javascript文档.Web API

我使用Web API来获取我的文档，使用如下:

[Route("Api/DocumentApi/DownloadDocument")]
    [HttpGet]
    public IHttpActionResult DownloadDocument(int documentID)
    {
        Document documentToDownload = new Document();
        using (TrustInvestmentSwitchEntities db = new TrustInvestmentSwitchEntities())
        {
            DocumentRepository repo = new DocumentRepository();
            documentToDownload = repo.GetSingle(db, x => x.ID == documentID);                
        }
        var stream = new MemoryStream();
        var result = new HttpResponseMessage(HttpStatusCode.OK)
        {
            Content = new ByteArrayContent(stream.GetBuffer())
        };
        result.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment")
        {
            FileName = documentToDownload.FileName
        };
        result.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
        var response = ResponseMessage(result);
        return response;            
    }

这看起来像是在检索文档。但是，我希望文档要么立即下载，要么显示一个弹出窗口，让用户选择保存文件的位置，而这并没有发生。建议立即下载

这是我的Javascript GET，我认为这是问题:

DocumentToDownload = $(that).closest('.document-item').data('documentid');
                var url = '/Api/DocumentApi/DownloadDocument';
                var data = {
                    DocumentID: DocumentToDownload
                };
                $.ajax({
                    type: "GET",
                    url: url,
                    contentType: "application/json",
                    data: data,
                    dataType: "json",
                    success: function (json, status) {
                        if (status != "success") {
                            log("Error loading data");
                            return;
                        }
                        log("Data loaded!");
                    },
                    error: function (result, status, err) {
                        log("Error loading data");
                        return;
                    }
                });

我不知道后面该放什么:

 success: function (json, status) {