How can I write a .NET application that will automatically go to www.yahoo.com?

The following code is not included in the yahoo system. How to rewrite it?

(Of course, the "username" and "password" will be replaced by my actual account name and password.)

    static void Main(string[] args)
    {
        string input = string.Format("username={0}&passwd={1}", "<username>", "<password>");

        WebRequest request = HttpWebRequest.Create("https://login.yahoo.com/config/login");
        request.Method = "POST";
        request.ContentType = "application/x-www-form-urlencoded";

        StreamWriter writer = new StreamWriter(request.GetRequestStream());
        writer.Write(input);
        writer.Close();

        StreamReader reader = new StreamReader(request.GetResponse().GetResponseStream());

        string x = reader.ReadToEnd();

        Console.Read();
    }