YaClient.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Security.Authentication;
using System.Threading.Tasks;
using CsQuery;
using Ya.Parser.Properties;

namespace Ya.Parser
{
    class Program
    {
        static void Main()
        {
            var client = new YaClient("login", "password");
            client.Login().Wait();
            var emails = client.GetEmailList().Result;
            foreach (var email in emails)
                Console.WriteLine("{0} : {1}", email.Item1, email.Item2);
            Console.ReadLine();
        }
    }

    public class YaClient
    {
        const HtmlParsingOptions HtmlOptions = HtmlParsingOptions.Default | HtmlParsingOptions.IgnoreComments;
        readonly string _login;
        readonly HttpClient _http;
        readonly string _password;
        readonly Settings _settings;

        public YaClient(string login, string password, Settings settings = null)
        {
            _settings = settings ?? Settings.Default;
            _login = login;
            _password = password;
            _http = CreateHttp();
        }

        public async Task Login()
        {
            try
            {
                var data = new Dictionary<string, string>
                {
                    {_settings.LoginInputName, _login},
                    {_settings.PasswordInputName, _password}
                };
                var form = new FormUrlEncodedContent(data);
                var resp = await _http.PostAsync(_settings.LoginUri, form);
                resp.EnsureSuccessStatusCode();
            }
            catch (Exception ex)
            {
                throw new AuthenticationException("Login failed", ex);
            }
        }

        public async Task<IEnumerable<Tuple<string, string>>> GetEmailList()
        {
            var emailPage = await GetPage(_settings.MailUri);
            return ParseMessages(emailPage);
        }

        IEnumerable<Tuple<string, string>> ParseMessages(string emailPage)
        {
            var dom = CreateDom(emailPage);
            var messages = dom.Find(".b-messages__message");
            return messages.Select(ParseMessage);
        }

        Tuple<string, string> ParseMessage(IDomObject msg)
        {
            var dom = msg.Cq();
            var fromSpan = dom.Find(".b-messages__from__text");
            var from = fromSpan.Text();
            var subjectSpan = dom.Find(".b-messages__subject");
            var subject = subjectSpan.Text();
            return Tuple.Create(from, subject);
        }

        HttpClient CreateHttp()
        {
            var handler = new HttpClientHandler
            {
                CookieContainer = new CookieContainer()
            };
            var client = new HttpClient(handler)
            {
                //todo: base uri?
            };
            foreach (var str in _settings.DefaultHeaders)
            {
                var header = ParseHeader(str);
                client.DefaultRequestHeaders.Add(header.Item1, header.Item2);
            }
            return client;
        }

        static Tuple<string, string> ParseHeader(string str)
        {
            var idx = str.IndexOf(":", StringComparison.InvariantCultureIgnoreCase);
            var key = str.Substring(0, idx).TrimEnd();
            var val = str.Substring(idx + 1).TrimStart().Trim('"');
            return Tuple.Create(key, val);
        }

        static CQ CreateDom(string content)
        {
            return new CQ(content, parsingOptions: HtmlOptions);
        }

        async Task<string> GetPage(string uri)
        {
            var resp = await _http.GetAsync(uri);
            resp.EnsureSuccessStatusCode();
            return await resp.Content.ReadAsStringAsync();
        }
    }
}