HTTP-POST method to login not

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C#

I am trying to login into a website using HTTP-POST method in c#

but the response i get is the login page itself not the logged in page?
Also i need a persistent session so i think i need to be using cookies is that correct? if yes how?

here is the html source snippet to login

<form onsubmit="return !(!this.PASSWORD.value||!this.USERNAME.value);" action="/login.html" method="post" name="loginform">

What I have tried:

class Program
    {
        static void Main(string[] args)
        {
            string username = "####";
            string password = "########";
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create("https://ftrpoker.com/login.html");
            request.Method = "POST";
            using (StreamWriter writer = new StreamWriter(request.GetRequestStream(), Encoding.ASCII))
            {
                writer.Write("USERNAME=" + username + "&PASSWORD=" + password);
            }

            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            //Retrieve your cookie that id's your session
            //response.Cookies

            using (StreamReader reader = new StreamReader(response.GetResponseStream()))
                Console.WriteLine(reader.ReadToEnd());
        }

    }