C# Web抓取网页内容资源不释放

Question

public String getContent(String url)
        {

            WebRequest req = WebRequest.Create(url);

            req.Method = "GET";
           
            HttpWebResponse resp = (HttpWebResponse)req.GetResponse();
            
            Stream stream = resp.GetResponseStream();
            
            StreamReader reader = new StreamReader(stream, Encoding.UTF8);
            String s = reader.ReadToEnd();
            stream.Close();
            reader.Close();
            //req.KeepAlive = false;
            resp.Close();
            req.Abort();


            if (resp != null)
            {
                resp.Close();
            }
            if (req != null)
            {
                req.Abort();
            }




            System.GC.Collect();

            Console.WriteLine("data");
            return s;
        }

再次调用时
基础连接已经关闭: 接收时发生错误。

=============================================================================
查找MSDN发现建议使用webclient

于是Fail again!

        public string getClientContent(String url)
        {
            string result = "false";
            using (var client = new HttpClient())
            {
                client.DefaultRequestHeaders.Accept.TryParseAdd("*/*");
                HttpResponseMessage res = client.GetAsync(string.Format(url)).Result;
                if (res.StatusCode == System.Net.HttpStatusCode.OK)
                {
                    result = res.Content.ReadAsStringAsync().Result;
                }
            }
            Console.WriteLine(result);
            return result;
        }