网络信息获取代码2------ 慕课第10 北大唐大壮

using System;
using System.Text;
using System.Text.RegularExpressions;//正则表达式
using System.IO;
using System.Net;

namespace _2
{
    class Program
    {
        static void Main(string[] args)
        {
            string url = @"http://www.baidu.com";
            if (args.Length != 0) url = args[0];
            string str = DownloadString(url);
            Console.WriteLine(str);
        }
        public static string DownloadString(string url)
        {
            try
            {
                HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
                request.Credentials = CredentialCache.DefaultCredentials;
                HttpWebResponse response = request.GetResponse() as HttpWebResponse;

                Stream responseStream = response.GetResponseStream();
                Encoding encoding = Encoding.UTF8; //Encoding.Default;
                StreamReader reader = new StreamReader(responseStream, encoding);
                string str = reader.ReadToEnd();
                reader.Close();
                responseStream.Close();
                response.Close();
                return str;
            }
            catch(UriFormatException exception)
            {
                Console.WriteLine(exception.Message.ToString());
                Console.WriteLine("Invalid url format.Please use https://www.yousitr.com");
            }
            catch(WebException exception2)
            {
                Console.WriteLine(exception2.Message.ToString());
            }
            return "";
        }
    }
}