C#: Create a WebRequest with HTTPClient

http://www.cnblogs.com/shanyou/archive/2012/03/21/2410739.html

http://msdn.microsoft.com/zh-cn/library/system.net.http.httpclient.aspx

http://code.msdn.microsoft.com/Introduction-to-HttpClient-4a2d9cee

　　　　using System.Net.Http;
　　　　public static string GetHttpResponse(string queryUrl)
        {

            try
            {
                HttpClientHandler handler = new HttpClientHandler();
                handler.UseDefaultCredentials = true;
                handler.CookieContainer = new CookieContainer();
                handler.UseCookies = true;
                handler.AllowAutoRedirect = true;

                using (HttpClient client = new HttpClient(handler))
                {
                    // Add a user-agent header
                    client.DefaultRequestHeaders.Add("user-agent", USERAGENT);
                    Console.WriteLine("update user agent {0}", client.DefaultRequestHeaders.UserAgent);

                    // add referer
                    client.DefaultRequestHeaders.Add("referer", REFERER);
                    Console.WriteLine("update referer {0}", client.DefaultRequestHeaders.Referrer);

                    //add accept
                    client.DefaultRequestHeaders.Add("accept", ACCEPT);
                    Console.WriteLine("update accept {0}", client.DefaultRequestHeaders.Accept);

                    // add accept-encoding
                    client.DefaultRequestHeaders.Add("accept-encoding", ACCEPTENCODING);
                    Console.WriteLine("update encoding {0}", client.DefaultRequestHeaders.AcceptEncoding);

                    // compose the url
                    string requestUrl = string.Format("{0}{1}", BINGDEXURL, queryUrl);
                    // send request
                    var result = client.GetAsync(requestUrl).Result;

                    string res = result.Content.ReadAsStringAsync().Result;
                    Console.WriteLine("res \n" + res);

                    File.WriteAllText(@"D:\temp2.html", res);
                    return res;
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(string.Format("Failed while getting response for {0} with below error message", queryUrl));
                Console.WriteLine(ex.Message);
            }
            return null;

        }