.Net c# Webrequest Post

Question

People I’m studying Webrequest, I’m trying to make a query on the site of the post office and so I read it should look like this:

WebRequest request = WebRequest.Create("http://www2.correios.com.br/sistemas/rastreamento/resultado.cfm");
        request.Method = WebRequestMethods.Http.Post;
        request.ContentType = "application/x-www-form-urlencoded";
        request.Credentials = CredentialCache.DefaultCredentials;

        using (var stream = request.GetRequestStream())
        {
            var buffer = Encoding.UTF8.GetBytes("objetos=PU633524761BR");
            stream.Write(buffer, 0, buffer.Length);
        }

        HttpWebResponse response = (HttpWebResponse)request.GetResponse();
        Console.WriteLine(response.StatusDescription);
        Stream dataStream = response.GetResponseStream();
        StreamReader reader = new StreamReader(dataStream);
        string responseFromServer = reader.ReadToEnd();
        textBox.Text = responseFromServer;
        Console.WriteLine(responseFromServer);
        reader.Close();
        dataStream.Close();
        response.Close();

however when running it is not showing the posting history of the object so that I can retrieve the information

Answer 1

I believe that you have confused with the order of the requests made by the page and that is why you are not emulating it correctly. Analyzing realized that she first makes a request on another page and then redirects to which you are trying to make the call (which will not work because as comes by cookies you will not have anything). The correct is more or less like this:

var request = (HttpWebRequest)WebRequest.Create("https://www2.correios.com.br/sistemas/rastreamento/ctrl/ctrlRastreamento.cfm?");  //alterado para o lugar correto do post, fiz um cast pra httpwebrequest para poder usar o cookiecontainer e assim tê-los na próxima página.
            request.Method = WebRequestMethods.Http.Post;
            var cookies = new CookieContainer();  //incluido cookie container
            request.CookieContainer = cookies;  //atribuido a requisição
            request.ContentType = "application/x-www-form-urlencoded";
            request.Credentials = CredentialCache.DefaultCredentials;

            using (var stream = request.GetRequestStream())
            {
                var buffer = Encoding.UTF8.GetBytes("objetos=PU633524761BR");
                stream.Write(buffer, 0, buffer.Length);
            }

            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            Console.WriteLine(response.StatusDescription);
            Stream dataStream = response.GetResponseStream();
            StreamReader reader = new StreamReader(dataStream);
            string responseFromServer = reader.ReadToEnd();
            Console.WriteLine(responseFromServer);
            reader.Close();
            dataStream.Close();
            response.Close();