查找word操作（支持多关键字查找）

using System;
using System.Net;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
using System.Net.Security;
using System.Security.Cryptography.X509Certificates;
using System.Collections;

namespace ConsoleApp1
{

    class Program
    {
        public static string DoRequest(string Url, string cookieStr)
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);
            request.Timeout = 1000 * 900;
            request.Headers.Add(HttpRequestHeader.Cookie, cookieStr);
            request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/31.0.1650.63 Safari/537.36";
            ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072;// SecurityProtocolType.Tls1.2;
            string back = "";
            try
            {
                WebResponse response = request.GetResponse();
                StreamReader reader = new StreamReader(response.GetResponseStream(), System.Text.Encoding.UTF8);
                back = reader.ReadToEnd();
                reader.Close();
                reader.Dispose();
                response.Close();
            }
            catch (Exception ex)
            {
                back = ex.Message;
            }
            return back;
        }

        static void Main(string[] args)
        {
            Console.WriteLine("请输入关键字数目");
            int num = int.Parse(Console.ReadLine());
            ArrayList keywords = new ArrayList();
            for (int i = 0; i < num; i++)
            {
                Console.WriteLine("请输入第" + (i + 1).ToString() + "个关键字而后输入回车");
                keywords.Add(Console.ReadLine());
            }
            string cookie = "";
            for (int i = 1; i < 64; i++)
            {
                string url = "https://www.php.cn/topic/word?p=" + i.ToString();
                string str = DoRequest(url, cookie);
                bool canPass = true;
                foreach (Object obj in keywords)
                    if (str.IndexOf(obj.ToString()) == -1)
                    {
                        canPass = false;
                        break;
                    }
                if (canPass)
                    Console.WriteLine(url);
            }
            Console.WriteLine("检索完毕");
            Console.ReadLine();
        }
    }
}