WebClient request 400 error?

Question

WPF

string url = html;//html- указывается адрес сайта
                    using (var webClient = new WebClient())
                    {
                        var pars = new NameValueCollection();
                        pars.Add("_csrf", connetn);//connetn предварительно спарсил данные 
                        pars.Add("SignupForm[track_id]", "");
                        pars.Add("SignupForm[su_type]", "partner");
                        pars.Add("SignupForm[anonymously]", "0");
                        pars.Add("SignupForm[username]", "123456789yrtytr");
                        pars.Add("SignupForm[email]", "[email protected]");
                        pars.Add("SignupForm[password]", "41526300");
                        pars.Add("SignupForm[repeatpassword]", "41526300");
                        pars.Add("track_id", "0");
                        var response = webClient.UploadValues(url, pars);
                        if (response == null)
                        {
                            label1.Content = "2";
                            return;
                        }
                        else
                        {
                            label.Content = "1";
                        }
                    }

Error 400. Bad request.

Here is the request.

Answer 1

sniffer in hand, if everything is ok, then write to the site developers.
Chewed the first question as best he could, watch the second one with a sniffer?