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我已经实现了一个简单的方法，它会定期轮询服务以获取公共 IP 地址。

Stopwatch sw = new Stopwatch();

while (true)
{
    Console.WriteLine("(HttpWebRequest)WebRequest.Create...");

    sw.Restart();
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://checkip.dyndns.org/");
    sw.Stop();

    Console.WriteLine("HttpWebRequest was created in {0} ms", sw.ElapsedMilliseconds);

    request.Proxy = null;

    sw.Restart();
    using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
    {
        sw.Stop();
        Console.WriteLine("Response was received in {0} ms", sw.ElapsedMilliseconds);

        StreamReader sr = new StreamReader(response.GetResponseStream());
        string responseStr = sr.ReadToEnd().Trim();

        string ipStr = (new Regex(@"\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}")).Matches(responseStr)[0].ToString();
        IPAddress address = IPAddress.Parse(ipStr);

        Console.WriteLine("IP: {0}", address.ToString());
    }

    Console.WriteLine();
    Thread.Sleep(60000);
}

该方法第一次WebRequest.Create创建该方法需要将近 10 秒，而在随后的调用中，几乎会立即创建相同的实例。HttpWebRequest这种行为的原因是什么？

更新。这是我从 Visual Studio 启动可执行文件（发布模式）时的输出。

(HttpWebRequest)WebRequest.Create...
HttpWebRequest was created in 9758 ms
Response was received in 683 ms

(HttpWebRequest)WebRequest.Create...
HttpWebRequest was created in 0 ms
Response was received in 617 ms

(HttpWebRequest)WebRequest.Create...
HttpWebRequest was created in 0 ms
Response was received in 1034 ms

(HttpWebRequest)WebRequest.Create...
HttpWebRequest was created in 0 ms
Response was received in 641 ms

(HttpWebRequest)WebRequest.Create...
HttpWebRequest was created in 0 ms
Response was received in 652 ms

(HttpWebRequest)WebRequest.Create...
HttpWebRequest was created in 0 ms
Response was received in 672 ms

(HttpWebRequest)WebRequest.Create...
HttpWebRequest was created in 0 ms
Response was received in 658 ms

(HttpWebRequest)WebRequest.Create...
HttpWebRequest was created in 0 ms
Response was received in 655 ms

(HttpWebRequest)WebRequest.Create...
HttpWebRequest was created in 0 ms
Response was received in 1067 ms

(HttpWebRequest)WebRequest.Create...
HttpWebRequest was created in 0 ms
Response was received in 651 ms

(HttpWebRequest)WebRequest.Create...
HttpWebRequest was created in 0 ms
Response was received in 643 ms

编辑：
我在具有 2 GB RAM、Intel Core 2 Duo T7500、下载连接速度为 7 Mbps 和上传速度为 640 Kbps 的计算机上使用 Windows 7 SP1 32 位。

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