using System;

using System.Net.Http;              

public class Program

{

    public static void Main()

    {

        var httpclient = HttpClientServiceB.Instance;

        var result = httpclient.GetAsync("").GetAwaiter().GetResult();

        var retb = result.Content.ReadAsStringAsync().GetAwaiter().GetResult();

        Console.WriteLine(retb);

        HttpClientServiceA shttpclient = new HttpClientServiceA();

        var resulta = shttpclient.HttpclientInstance.GetAsync("").GetAwaiter().GetResult();

        var reta = resulta.Content.ReadAsStringAsync().GetAwaiter().GetResult();

        Console.WriteLine(reta);

    }

}

//static

public class HttpClientServiceA

{

    private static readonly HttpClient _httpClient;

    static HttpClientServiceA()

    {

        _httpClient = new HttpClient();

        _httpClient.BaseAddress = new Uri("http://blog.yowko.com/");

        _httpClient.DefaultRequestHeaders.ConnectionClose = true;

    }

    public HttpClient HttpclientInstance = _httpClient;

}

//singleton

public sealed class HttpClientServiceB

{

    private static readonly Lazy<HttpClient> lazy = new Lazy<HttpClient>(

        () =>

        {

            var baseUri = new Uri("http://blog.yowko.com");

            var result = new HttpClient();

            result.BaseAddress = baseUri;

            //設定 1 分鐘沒有活動即關閉連線，預設 -1 (永不關閉)

            //ServicePointManager.FindServicePoint(baseUri).ConnectionLeaseTimeout = (int)TimeSpan.FromMinutes(1).TotalMilliseconds;

            //設定 1 分鐘更新 DNS，預設 120000 (2 分鐘)

            //ServicePointManager.DnsRefreshTimeout = (int)TimeSpan.FromMinutes(1).TotalMilliseconds;

            return result;

        });

    public static HttpClient Instance { get { return lazy.Value; } }

    private HttpClientServiceB() { }

}