取网页的一个函数

internal string GetWebContent(Uri uri)
        {
            string tempCode = null;
            string error = null;
            int time = 0;
            HttpWebResponse response = null;
            HttpWebRequest request = null;
            do                                                               //访问失败时重新访问，最多重新访问4次
            {
                WebProxy proxy = new WebProxy("代理网站", false);
                proxy.Credentials = new NetworkCredential(@"用户名", "密码", "");
                request = HttpWebRequest.Create(uri.AbsoluteUri) as HttpWebRequest;
                Thread.Sleep(30);
                request.AllowAutoRedirect = true;
                request.Proxy = proxy;                                          //使用了代理
                int a = 0;
                time += 1;
                error = null;
                try
                {
                    DateTime now = DateTime.Now;
                    response = request.GetResponse() as HttpWebResponse;
                    TimeSpan t = DateTime.Now - now;
                }
                catch (Exception ex)
                {
                    tempCode = ex.Message;
                    error = ex.Message;
                }
            } while (error != null && time < 4);
            System.IO.Stream resStream = null;
            StreamReader sr = null;

            try
            {
                resStream = response.GetResponseStream();
                sr = new StreamReader(resStream, Encoding.UTF8);
                tempCode = sr.ReadToEnd();
                response.Close();
                resStream.Close();
                sr.Close();

            }
            catch (Exception e)
            {}            
            return tempCode;
        }