Post v.17.12

        private static void LoadPostFormDataAsync()
        {
            var values = new Dictionary<string, string>
            {   { "comments", "Demo" },
                { "custemail", "example@example.com"},
                { "custname", "John Silver" },
                { "custtel", "+380991234567" },
                { "delivery", "11:00" },
                { "size", "medium"}
            };

            var stream = GetStreamAsync(RequestUri, values).Result;
            try
            {
                _document = new HTMLDocument(stream, RequestUri);
                Console.WriteLine(_document.Body.InnerHTML);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
        }

        private static async Task<Stream> GetStreamAsync(string requestUri, Dictionary<string, string> formData)
        {
            System.Net.Http.HttpClient client = new System.Net.Http.HttpClient();
            var content = new System.Net.Http.FormUrlEncodedContent(formData);
            var response = await client.PostAsync(requestUri, content);
            return await response.Content.ReadAsStreamAsync();
        }

        private static void LoadDocumentWithBasicAuth()
        {
            var requestMessage = new BasicAuthRequestMessage("user1", "passwd1", "https://httpbin.org/basic-auth/user1/passwd1");
            try
            {
                _document = new HTMLDocument(requestMessage);
                Console.WriteLine(_document.Body.InnerHTML);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
        }