uploading a file and form Data in web Api and angularJS

public string UploadImage()
    {
        HttpRequestMessage request = this.Request;
        if (!request.Content.IsMimeMultipartContent())
        {
            throw new HttpResponseException(new HttpResponseMessage((HttpStatusCode.UnsupportedMediaType)));
        }
        var context = HttpContext.Current.Request;
        if (context.Files.Count > 0)
        {
            var resourcePhoto = new PhotoHelper(HttpContext.Current.Server.MapPath("~"));
            var file = context.Files.AllKeys.FirstOrDefault();
            var result = resourcePhoto.SaveResourceImage(context.Files[file], User.Identity.Name);
            return result;
        }
        else
        {
            return null;
        }
    }

And in the SaveResourceImage I do the following:

 postedFile.SaveAs(resultPath);