C#图解教程(第5版) 同步方法

当青春邂逅吉米多维奇2026-10-11 12:40

第21章异步编程

21.1节什么是异步

示例1 在.net framework环境下运行，增加代码

cs 复制代码

wc1.Headers.Add(HttpRequestHeader.UserAgent,
    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36");
wc1.Headers.Add(HttpRequestHeader.Accept,
    "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8");
wc1.Headers.Add(HttpRequestHeader.AcceptLanguage, "zh-CN,zh;q=0.9,en;q=0.8");
wc1.Headers.Add(HttpRequestHeader.Referer, "https://www.baidu.com/");  // 部分站点校验 Referer

wc1.Encoding = Encoding.UTF8;

完整代码如下：

cs 复制代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net;
using System.Diagnostics;

namespace ConsoleApp128
{
    class MyDownloadString 
    {
        Stopwatch sw = new Stopwatch();
        public void DoRun()
        {
            const int LargeNumber = 6_000_000;
            sw.Start();
            int t1 = CountCharacters(1,"http://www.microsoft.com");
            int t2 = CountCharacters(2,"http://illustratedcsharp.com");
            CountToALargeNumber(1,LargeNumber);
            CountToALargeNumber(2, LargeNumber);
            CountToALargeNumber(3, LargeNumber);
            CountToALargeNumber(4, LargeNumber);
            Console.WriteLine($"Chars in https://www.iduba.com/:{t1}");
            Console.WriteLine($"Chars in http://illustratedcsharp.com:{t2}");
        }
        private int CountCharacters(int id, string uriString)
        {
            var wc1 = new WebClient();
            Console.WriteLine("Starting call{0}:{1,4:N0}ms",id,sw.Elapsed.TotalMilliseconds);
            //string result = wc1.DownloadString(uriString);
            wc1.Headers.Add(HttpRequestHeader.UserAgent,
                "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/124.0.0.0 Safari/537.36");
            wc1.Headers.Add(HttpRequestHeader.Accept,
                "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8");
            wc1.Headers.Add(HttpRequestHeader.AcceptLanguage, "zh-CN,zh;q=0.9,en;q=0.8");
            wc1.Headers.Add(HttpRequestHeader.Referer, "https://www.baidu.com/");  // 部分站点校验 Referer

            wc1.Encoding = Encoding.UTF8;
            string result = wc1.DownloadString(uriString);

            Console.WriteLine("Call{0} completed:{1,4:N0} ms",id,sw.Elapsed.TotalMilliseconds);
            return result.Length;
        }
        private void CountToALargeNumber(int id, int value)
        {
            for (long i = 0; i < value; i++)
                ;
            Console.WriteLine("End counting{0}:{1,4:N0} ms", id,sw.Elapsed.TotalMilliseconds);
        }
    }
    internal class Program
    {
        static void Main(string[] args)
        {
            MyDownloadString ds = new MyDownloadString();
            ds.DoRun();
        }
    }
}