C#访问http(转)

//访问并返回源代码
protected string GetPageContent(string getpage)
        {
            try
            {
                CookieContainer cc = new CookieContainer();
                string content = string.Empty;
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(getpage);
                request.Method = "post";
                request.Timeout = 10000;
                request.ContentType = "application/x-www-form-urlencoded";
                request.ContentLength = content.Length;//????
                request.UserAgent = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; Maxthon; .NET CLR 1.1.4322)";
                //request.UserAgent = "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/525.13 (KHTML, like Gecko) Chrome/0.2.149.27 Safari/525.13";
                request.CookieContainer = cc;

                Stream stream = request.GetRequestStream();

                StreamWriter writer = new StreamWriter(stream, Encoding.GetEncoding("gb2312"));
                writer.Write(content, 0, content.Length);
                writer.Close();
                stream.Close();

                HttpWebResponse response = request.GetResponse() as HttpWebResponse;
                response.Cookies = cc.GetCookies(request.RequestUri);
                Stream readerStream = response.GetResponseStream();
                StreamReader sr = new StreamReader(readerStream, Encoding.GetEncoding("gb2312"));
                content = sr.ReadToEnd();
                sr.Close();
                readerStream.Close();
                return content;
            }
            catch (Exception e)
            {
                Exception e1 = e;
                return null;
            }
        }

//只访问
private bool callurl(string url)
        {
            //string html = null;
            WebRequest req = WebRequest.Create(url);
            req.Timeout = 100000000;
            WebResponse res = req.GetResponse();
            Stream receiveStream = res.GetResponseStream();
            Encoding encode = Encoding.GetEncoding("gb2312");
            StreamReader sr = new StreamReader(receiveStream, encode);
            char[] readbuffer = new char[256];
            int n = sr.Read(readbuffer, 0, 256);
            if (n > 0) { return true; } else { return false; }
        }