C graphical tutorial (Fourth Edition)_ Chapter 20 asynchronous programming: examples - cases without asynchronous

using System;
using System.Net;
using System.Diagnostics;

namespace Chapter20AsyncSample_WithoutUsingAsyncP394
{
    class MyDownloadingString
    {
        Stopwatch sw=new Stopwatch();// class System.Diagnostic.Stopwatch: Provides a set of methods and properties
                                     //that you can use to accurately measure elapsed time.

        public void DoRun()
        {
            const int LargeNumber = 6000000;
            sw.Start();
            int t1 = CountCharacters(1,"http://www.baidu.com"); 
            int t2 = CountCharacters(2, "http://www.csdn.net");
            CountToALargeNumber(1,LargeNumber); CountToALargeNumber(2, LargeNumber);
            CountToALargeNumber(3,LargeNumber); CountToALargeNumber(4, LargeNumber);

            Console.WriteLine("Chars in http://www.baidu.com   :{0}", t1);
            Console.WriteLine("Chars in http://www.csdn.net    :{0}", t2);
        }
        private int CountCharacters(int id,string uriString)
        {
            WebClient wc1 = new WebClient();// class System.Net.WebClient  Provide a common method for obtaining information from resources （ use URI identification ） Send and receive data .
            Console.WriteLine("Starting call {0}:{1,4:N0} ms",id,sw.Elapsed.TotalMilliseconds);

            string result = wc1.DownloadString(new Uri(uriString));// Download the resource as a string . Returns a string 
            Console.WriteLine("  Call {0} completed:{1,4:N0} ms",id,sw.Elapsed.TotalMilliseconds);
            //Console.WriteLine("{0}", result);
            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);
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            MyDownloadingString ds = new MyDownloadingString();
            ds.DoRun();
            Console.WriteLine("Hello World!");
        }
    }
}