Webbrowser.navigate fails to login the first time
string username = "username";
        string password = "pass";
        string login = "login";
        string _urlLogin = "http:xxxxxxx";
        Uri _uriLogin = new Uri(_urlLogin);
        string _postData = "userName=" + username + "&pwd=" + password + "&loginTrue=" + login;
        byte[] data = Encoding.UTF8.GetBytes(_postData);
        webBrowser1.Navigate(_uriLogin, data, "Content-Type: application/x-www-form-urlencoded");`