c# http post 带参数

var url = "http:/xxx";

            var credential = "fooClientIdPassword:secret";
            var userName = "xx";
            var pwd = "xx";

            var base64Credential = Convert.ToBase64String(Encoding.Default.GetBytes(credential));



            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            request.Method = "POST";
            request.ContentType = "application/x-www-form-urlencoded";
            request.Accept = "Application/json";
            request.Headers.Add("Authorization", "Basic " + base64Credential);


            var content = $"grant_type=password&username={userName}&password={pwd}";
            var data = Encoding.UTF8.GetBytes(content);
            request.ContentLength = data.Length;

            var requestStream = request.GetRequestStream();

            requestStream.Write(data, 0, data.Length);
            requestStream.Close();



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

            var responseStream = response.GetResponseStream();

            using (StreamReader sr = new StreamReader(responseStream))
            {
                var s = sr.ReadToEnd();
                Console.WriteLine(s);
            }

            Console.Read();