angular toPromise call that returns csvFile

I have to write the promise call and component method to call the webAPI that returns csv file. I can see, my code wont work without creating a proper header. Please let me know, how I can fix this issue

Component:

---

downloadfile() { this.isLoading = true; this.customerMonitoringService.getMyFileFromBackend(this.productionDataUrl).subscribe( res => { this.isLoading = false; res; }, (error: any) => Observable.throw(error || 'Server error') ); }

cust-monitoring.service.ts

---

getMyFileFromBackend(productionURL: string): Observable {

    return this.http.get("`"+productionURL+"`")
        .map(res => res.text())
            .catch((error: any) => Observable.throw(error || 'Server error'));
}

Web API call

---

    [HttpGet]
    [HttpPost]
    public async Task<IHttpActionResult> Index(string systemName)
    {
          var negotiator = Configuration.Services.GetContentNegotiator();

        var mediaTypeFormatterCollection = new MediaTypeFormatterCollection();
        mediaTypeFormatterCollection.Clear();
        mediaTypeFormatterCollection.Add(new ProductionPeriodFormatter());
        mediaTypeFormatterCollection.Add(new JsonMediaTypeFormatter());

        var result = negotiator.Negotiate(typeof(ProductionPeriod), Request, mediaTypeFormatterCollection);
        if (result == null)
            throw new HttpResponseException(new HttpResponseMessage(HttpStatusCode.NotAcceptable));

        var production = await Production(systemName);
        var content = new ObjectContent<ProductionPeriod>(
            production,
            result.Formatter,
            result.MediaType.MediaType
        );
        if (result.Formatter is JsonMediaTypeFormatter)
        {
            ((JsonMediaTypeFormatter) result.Formatter).SerializerSettings.ContractResolver =
                new CamelCasePropertyNamesContractResolver();
            content.Value = new ProductionPeriod(production.Start, production.End, production.TimeZone, interval.Value,
                NormalizedIntervals(production, interval.Value));
        }
        else
        {
            try
            {
                WebRequest.DefaultWebProxy = null;

                content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
                {
                    FileName = "production.csv"
                };
            }
            catch (Exception ex)
            {
                string msg = "";
                msg = ex.Message.ToString();
            }
        }

        var response = new HttpResponseMessage()
        {
            Content = content
        };

        return ResponseMessage(response);
    }