c# 查询本机可用的代理ip

 string strUrl = "https://www.xicidaili.com/nt/";
            HttpHelper httpProxy = new HttpHelper();
            for (int i = 1; i <= 728; i++)
            {
                string strHtml = httpProxy.Get_Request(strUrl + i, httpProxy.cookie, "www.xicidaili.com", "https://www.xicidaili.com/nt/", blnHttps: true, strAccept: "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3", strUserAgent: "Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/73.0.3683.86 Safari/537.36");
                HtmlAgilityPack.HtmlDocument docList = new HtmlAgilityPack.HtmlDocument();
                docList.LoadHtml(strHtml);
                var trListNodes = docList.DocumentNode.SelectNodes("//*[@id=\"ip_list\"]/tr");
                for (int j = 1; j < trListNodes.Count; j++)
                {
                    var trNode = trListNodes[j];
                    string strIp = trNode.SelectSingleNode("td[2]").InnerText.Trim();
                    string strPort = trNode.SelectSingleNode("td[3]").InnerText.Trim();
                    int intPort = int.Parse(strPort);
                    try
                    {
                        WebProxy proxyObject = new WebProxy(strIp, intPort);// port为端口号 整数型
                        HttpWebRequest Req = WebRequest.Create("http://www.bookschina.com") as HttpWebRequest;
                        Req.Proxy = proxyObject; //设置代理
                        Req.Timeout = 2000;   //超时
                        DateTime dt = DateTime.Now;
                        var Resp = (HttpWebResponse)Req.GetResponse();
                        Encoding bin = Encoding.GetEncoding("gb2312");
                        StreamReader sr = new StreamReader(Resp.GetResponseStream(), bin);
                        string str = sr.ReadToEnd();
                        sr.Close();
                        sr.Dispose();
                        var time = (DateTime.Now - dt).TotalMilliseconds;
                        Console.WriteLine(strIp + "   " + intPort + " " + time);
                    }
                    catch
                    { }
                }

            }

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Security;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Threading.Tasks;

namespace TestProxy
{
    public class HttpHelper
    {
        public CookieContainer cookie;
        public HttpHelper()
        {
            cookie = new CookieContainer();
        }
        private static bool CheckValidationResult(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors errors)
        {
            return true; //总是接受     
        }
        public string Get_Request(
            string strUrl,
            CookieContainer _cookie = null,
            string strHost = "",
            string strRefer = "",
            string strOrigin = "",
            Dictionary<string, string> lstHeads = null,
            string strEncoding = "utf-8",
            string strContentType = "",
            string strAccept = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
            string strUserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36",
            bool blnAllowAutoRedirect = true,
            int intTimeout = 1000 * 30,
            bool blnHttps = false,
            System.Net.WebProxy proxy = null)
        {
            HttpWebRequest request;
            HttpWebResponse response;
            request = (HttpWebRequest)WebRequest.Create(strUrl);
            request.Accept = strAccept;
            request.Timeout = intTimeout;
            request.Method = "GET";
            request.Credentials = CredentialCache.DefaultCredentials;
            request.UserAgent = strUserAgent;
            request.AllowAutoRedirect = blnAllowAutoRedirect;
            if (blnHttps)
            {
                ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
                request.ProtocolVersion = HttpVersion.Version10;

                ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

            }
            if (!string.IsNullOrEmpty(strContentType))
            {
                request.ContentType = strContentType;
            }
            if (_cookie != null)
            {
                request.CookieContainer = _cookie;
            }
            if (!string.IsNullOrEmpty(strHost))
            {
                request.Host = strHost;
            }
            if (!string.IsNullOrEmpty(strRefer))
            {
                request.Referer = strRefer;
            }
            if (!string.IsNullOrEmpty(strOrigin))
            {
                request.Headers.Add("Origin", strOrigin);
            }
            if (lstHeads != null && lstHeads.Count > 0)
            {
                foreach (var item in lstHeads)
                {
                    request.Headers.Add(item.Key, item.Value);
                }
            }
            
            if (proxy != null)
                request.Proxy = proxy;
            response = (HttpWebResponse)request.GetResponse();
            var sr = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding(strEncoding));
            string strResult = sr.ReadToEnd();
            sr.Close();
            request.Abort();
            response.Close();
            return strResult;

        }

        public string POST_Request(
            string strUrl,
            string postDataStr,
            CookieContainer _cookie = null,
            string strHost = "",
            string strRefer = "",
            string strOrigin = "",
            Dictionary<string, string> lstHeads = null,
            string strEncoding = "utf-8",
            string strContentType = "",
            string strAccept = "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
            string strUserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.101 Safari/537.36",
            bool blnAllowAutoRedirect = true,
            int intTimeout = 1000 * 30,
            bool blnHttps = false,
            System.Net.WebProxy proxy = null)
        {
            HttpWebRequest request;
            HttpWebResponse response;
            request = (HttpWebRequest)WebRequest.Create(strUrl);
            request.Accept = strAccept;
            request.Timeout = intTimeout;
            request.Method = "POST";
            request.Host = strHost;
            request.UserAgent = strUserAgent;
            if (_cookie != null)
            {
                request.CookieContainer = _cookie;
            }
            if (blnHttps)
            {
                ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
                request.ProtocolVersion = HttpVersion.Version10;

                ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

            }
            request.AllowAutoRedirect = blnAllowAutoRedirect;
            if (!string.IsNullOrEmpty(strContentType))
            {
                request.ContentType = strContentType;
            }
            if (!string.IsNullOrEmpty(strOrigin))
            {
                request.Headers.Add("Origin", strOrigin);
            }
            if (!string.IsNullOrEmpty(strRefer))
            {
                request.Referer = strRefer;
            }
            if (!string.IsNullOrEmpty(strHost))
            {
                request.Host = strHost;
            }
            if (lstHeads != null && lstHeads.Count > 0)
            {
                foreach (var item in lstHeads)
                {
                    request.Headers.Add(item.Key, item.Value);
                }
            }
            if (!string.IsNullOrEmpty(postDataStr))
            {
                request.ContentLength = postDataStr.Length;
                Stream myRequestStream = request.GetRequestStream();
                StreamWriter myStreamWriter = new StreamWriter(myRequestStream);
                myStreamWriter.Write(postDataStr);
                myStreamWriter.Close();
            }
            if (proxy != null)
                request.Proxy = proxy;
            response = (HttpWebResponse)request.GetResponse();
            var sr = new StreamReader(response.GetResponseStream(), Encoding.GetEncoding(strEncoding));
            string strResult = sr.ReadToEnd();
            sr.Close();
            request.Abort();
            response.Close();
            return strResult;
        }

        public string DownloadFile(
            string strURLAddress,
            string strPath,
            CookieContainer _cookie = null,
            string strHost = "",
            string strRefer = "",
            string strOrigin = "",
            Dictionary<string, string> lstHeads = null,
            string strAccept = "",
            string strUserAgent = "",
            bool blnHttps = false,
            System.Net.WebProxy proxy = null)
        {
            try
            {
                // 设置参数
                HttpWebRequest request = WebRequest.Create(strURLAddress) as HttpWebRequest;
                if (!string.IsNullOrEmpty(strAccept))
                {
                    request.Accept = strAccept;
                }
                if (blnHttps)
                {
                    ServicePointManager.ServerCertificateValidationCallback = new RemoteCertificateValidationCallback(CheckValidationResult);
                    request.ProtocolVersion = HttpVersion.Version10;

                    ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

                }
                if (!string.IsNullOrEmpty(strUserAgent))
                {
                    request.UserAgent = strUserAgent;
                }
                if (_cookie != null)
                {
                    request.CookieContainer = _cookie;
                }
                if (!string.IsNullOrEmpty(strOrigin))
                {
                    request.Headers.Add("Origin", strOrigin);
                }
                if (!string.IsNullOrEmpty(strRefer))
                {
                    request.Referer = strRefer;
                }
                if (!string.IsNullOrEmpty(strHost))
                {
                    request.Host = strHost;
                }
                if (lstHeads != null && lstHeads.Count > 0)
                {
                    foreach (var item in lstHeads)
                    {
                        request.Headers.Add(item.Key, item.Value);
                    }
                }
                if (proxy != null)
                    request.Proxy = proxy;
                request.Timeout = 2000;
                //发送请求并获取相应回应数据
                HttpWebResponse response = request.GetResponse() as HttpWebResponse;
                string strReceivePath = string.Empty;

                //直到request.GetResponse()程序才开始向目标网页发送Post请求
                Stream responseStream = response.GetResponseStream();
                //创建本地文件写入流
                Stream stream = new FileStream(strPath, FileMode.Create);
                byte[] bArr = new byte[1024];
                int size = responseStream.Read(bArr, 0, (int)bArr.Length);
                while (size > 0)
                {
                    stream.Write(bArr, 0, size);
                    stream.Flush();
                    size = responseStream.Read(bArr, 0, (int)bArr.Length);
                }
                stream.Close();
                responseStream.Close();
                return strPath;
            }
            catch (Exception ex)
            {
                return "";
            }
        }

    }
}