var request = (HttpWebRequest)WebRequest.Create("https://www.roblox.com/NewLogin");

            var postData = "Username=user";
            postData += "&password=password";
            postData += "&ReturnUrl=";
            var data = Encoding.ASCII.GetBytes(postData);
            request.Method = "POST";
            request.AllowAutoRedirect = false;
            request.UserAgent = "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Firefox/45.0";
            request.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
            request.KeepAlive = true;
            request.ContentType = "application/x-www-form-urlencoded";
            request.ContentLength = data.Length;

            using (var stream = request.GetRequestStream())
            {
                stream.Write(data, 0, data.Length);
            }

            var response = (HttpWebResponse)request.GetResponse();

            var responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();
            File.WriteAllText(@"C:\Users\Bon\Desktop\New Text Document.txt",responseString);
            Console.ReadLine();