WebClient wc = new WebClient();

Stream stm = wc.OpenRead(str_url);

StreamReader sr = new StreamReader(stm,Encoding.UTF8);

//Encoding这个类的属性有：UTF8,Unicode等等

Console.Write(sr.ReadToEnd());

HttpWebRequest hwrq = (HttpWebRequest)WebRequest.Create(str_url);

HttpWebResponse hwrp = (HttpWebResponse)hwrq.GetResponse();

StreamReader sr = new StreamReader(hwrp.GetResponseStream(),Encoding.UTF8);

Console.Write(sr.ReadToEnd());

Stream st = WebRequest.Create(str_url).GetResponse().GetResponseStream();

StreamReader str = new StreamReader (st,Encoding.UTF8);

Console .Write(str.ReadToEnd ());

string str_url = "http://www.baidu.com/";

WebClient wclient = new WebClient();

string str_content = wclient.DownloadString(str_url);

byte[] bt_content = new byte[str_content.Length];

bt_content = Encoding.Default.GetBytes(str_content); //此处不可吧Default转换成UTF8，否则造成转了两次，就乱码了。

str_content = Encoding.UTF8.GetString(bt_content);

Console.WriteLine(str_content);

Console.Write("Press any key to continue . . . ");

Console.ReadKey(true);