//设定您要取得得页面地址给url
string url = "http://www.cnblogs.com";
Uri contentUrl = new Uri(url);
WebRequest req = WebRequest.Create(contentUrl);
//设定为默认的认证方法
req.Credentials = CredentialCache.DefaultCredentials;
WebResponse resp = req.GetResponse();
Stream stream = resp.GetResponseStream();
StreamReader sr = new StreamReader(stream);
this.textBox2.Text = sr.ReadToEnd();
sr.Close();