C# multipart/form-data upload

FileUpload.cs

        public static async Task sendScreenShotResult(string fullPath, string game_code)
        {
            LogHandler _LogHandler = new LogHandler();
            try
            {
                var url = Config.HOST + "/api/battle/sendScreenShotResult/" + game_code;
                string filename = Path.GetFileName(fullPath);
                string CT = "image/jpeg";
                FormUpload.FileParameter f = new FormUpload.FileParameter(File.ReadAllBytes(fullPath), filename, "multipart/form-data");
                Dictionary<string, object> d = new Dictionary<string, object>();
                d.Add("file", f);
                string ua = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/535.2 (KHTML, like Gecko) Chrome/15.0.874.121 Safari/535.2";
                FormUpload.MultipartFormDataPost(url, ua, d);
                _LogHandler.SendLog("EVENT_LOBBY", "Screenshots enviados.");
            }
            catch(Exception ex)
            {
                _LogHandler.SendLog("HTTP_ERROR", "Falha ao enviar screenshots: " + ex);
            }
            

        }