How to add another parameter to formdata in AngularJS

I am sending a file object to my server from angularJS like this - 

var fd = new FormData();
            fd.append('file', file);

            var deferred = $q.defer();
            $http.post(uploadUrl, fd, {
                transformRequest: angular.identity,
                headers: {'Content-Type': undefined}
                }).success(function(data, status, headers, config){
                        deferred.resolve(data);
                })
                .error(function(data, status, headers, config){
                        deferred.reject('some error occurred');
                });

This is my Asp.Net MVC controller - 

public HttpResponseMessage Post([FromBody]HttpPostedFileBase file)

I want to send one more parameter (say userId) with the same request. Is it possible to do so? How should I recieve it at the server end. I tried adding fd.append('userId', userId) to the formdata object, but it didn't work. Please tell how to achieve this.

Thanks in advance.

Edit1: When I do bind like I mention, I get below error:

Can't bind multiple parameters ('file' and 'userId') to the request'scontent.

Edit2: I also tried creating an object like so - 

public class PostedInfo{
    public HttpPostedFileBase file {get;set;}
    public string userId {get;set;}        
}

and changed post method to - 

public HttpResponseMessage Post([FromBody]PostedInfo fd)

But, now this error is thrown, which is quite obvious as the request is json - 

The request entity's media type 'multipart/form-data' is not supported for this resource.

Not sure how to tell tell that fd.file is a multipart/form-data entity.

I finally figured this out. The issue is that HttpPostedFileBase seems to not work quite well with webapi, so instead one should use MultipartFormDataStreamProvider for this. Code below - 

    [HttpPost]
    public async Task<HttpResponseMessage> Post()
    {
        if (Request.Content.IsMimeMultipartContent())
        {
            string path = HttpContext.Current.Server.MapPath("~/Resources");
            var provider = new MultipartFormDataStreamProvider(path);
            await Request.Content.ReadAsMultipartAsync(provider);
            // get the additional parameter
            var userId = provider.FormData.GetValues("userId").FirstOrDefault();

            string filepath = provider.FileData[0].LocalFileName;

            return <your_custom_response_here>;
    }

Here, you can see, I also got the userId in the server code apart from uploading the file.

Well, MultipartFormDataStreamProvider will save the file with a cryptic name (BodyPart_...). You can get rid of that by building your own CustomMultipartFormDataStreamProvider. Found an awesome link as to how to format the file name while saving. Worth a read.