using system;
using system.collections.generic;
using system.text;
using system.net;
using system.io;

namespace thief
{
    class program
    {
        static void main(string[] args)
        {
           
            try {
                webclient mywebclient = new webclient();

                mywebclient.credentials = credentialcache.defaultcredentials;//獲取或設置用于對向internet資源的請求進行身份驗證的網(wǎng)絡憑據(jù)。

                byte[] pagedata = mywebclient.downloaddata("http://www.163.com");//從指定網(wǎng)站下載數(shù)據(jù)

                string pagehtml = encoding.default.getstring(pagedata);  //如果獲取網(wǎng)站頁面采用的是gb2312，則使用這句             

                //string pagehtml = encoding.utf8.getstring(pagedata); //如果獲取網(wǎng)站頁面采用的是utf-8，則使用這句

                console.writeline(pagehtml);//在控制臺輸入獲取的內容

                using (streamwriter sw = new streamwriter("c://test//ouput.html"))//將獲取的內容寫入文本
                {
                    sw.write(pagehtml);
                }

                console.readline(); //讓控制臺暫停,否則一閃而過了              
            }

            catch(webexception webex) {
                console.writeline(webex.message.tostring());
            }
        }
    }
}

注：內容轉自菩提樹下的楊過的博客