HttpWebRequest request =(HttpWebRequest)(WebRequest.Create("http://www.sina.com.cn")); 
HttpWebResponse response =(HttpWebResponse)request.GetResponse(); 
if(response.StatusCode==HttpStatusCode.OK)//因为发送的是HTTP请求，所以可以强制转换成HttpWebResponse，用以获取它的StatusCode,这是表示请求状态
{
Stream resStream =response.GetResponseStream();
StreamReader sr = new StreamReader(resStream, System.Text.Encoding.Default); 
string tempCode = sr.ReadToEnd(); 
resStream.Close(); 
sr.Close();
}