.net core 下使用httpClient获取压缩的网页

HttpClient是.net core 下使用比较频繁的http客户端了，其又有官方支持的HttpClientFactory，可谓强大之际。为了获取特定网站的网页，可以建立一个连接池供使用，效率很高。

这里以百度为例，并支持自动解压缩。

var sc = new ServiceCollection()
                .AddHttpClient("baidu", c =>
                {
                    c.BaseAddress = new Uri("https://baijiahao.baidu.com/");
                    c.DefaultRequestHeaders.Add("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3");
                    c.DefaultRequestHeaders.Add("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.86 Safari/537.36");
                })
                .ConfigurePrimaryHttpMessageHandler(messageHandler =>
                {
                    var handler = new HttpClientHandler();
                    if (handler.SupportsAutomaticDecompression)
                    {
                        handler.AutomaticDecompression = DecompressionMethods.Deflate | DecompressionMethods.GZip;
                    }
                    return handler;
                }).AddTransientHttpErrorPolicy(p =>
                    p.WaitAndRetryAsync(3, _ => TimeSpan.FromMilliseconds(600)));