senddata.cs

public static class SendData
    {
        readonly static string BASEURL = "https://www.someurl.com/api";
        static string Url;

        public static HttpWebRequest SetupRequest
        {
            get
            {
                var request = WebRequest.Create(Url) as HttpWebRequest;
                request.Method = "POST";
                request.ContentType = "multipart/form-data";
                return request;
            }
        }

        public static async Task<bool> HttpPost(MediaFile source, string token, string id, string folderid)
        {
            var res = await HttpPost(source, token, new FilesBase{ ACCid = id, FOLDERid = folderid });  
            return res;
        }

        public static async Task<bool> HttpPost(MediaFile source, string token, FilesBase files)
        {
            var Url = string.Format("{0}/upload/{1}/{2}/{3}", BASEURL, token, files.ACCid, files.FOLDERid);
            byte[] fileArr = null;
            DependencyService.Get<INetwork>().NetworkSpinner(true);
            try
            {
                using (var streamReader = new StreamReader(source.Source))
                {
                    using (var memstream = new MemoryStream())
                    {
                        streamReader.BaseStream.CopyTo(memstream);
                        fileArr = memstream.ToArray();
                    }
                }

                var imageStream = new ByteArrayContent(fileArr);
                imageStream.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
                {
                    FileName = Guid.NewGuid().ToString() + ".jpg"
                };

                var multi = new MultipartContent();
                multi.Add(imageStream);

                using (var client = new HttpClient())
                {  
                    client.BaseAddress = new Uri(BASEURL);  
                    var response = await client.PostAsync(new Uri(Url), multi);
                    DependencyService.Get<INetwork>().NetworkSpinner(false);
                    return response.IsSuccessStatusCode;
                } 
            }
            catch (Exception ex)
            {
                Debug.WriteLine("Exception sending data - {0}:{1}", ex.Message, ex.InnerException);
                DependencyService.Get<INetwork>().NetworkSpinner(false);
                return false;
            }
        }