HttpWebRequest 与 HttpWebResponse用法 小记

一、HttpWebRequest、HttpWebResponse

使用这两个类可以使开发出来的应用程序向统一资源标识符（URI）发出请求，并从该资源中获得响应。

.NET Framework给 WebRequest和WebResponse类提供了3个派生类，它们可以通过HTTP、FTP和file://协议与特定的端点通信。

 

二、使用HttpWebRequest检索Web页面

/// <summary> /// 使用HttpWebRequest检索Web页面 /// httpwebrequest与httpwebresponse这两个类使用http /// 协议进行通信。其最知名的用法是，是编写出来的应用程序 /// 可以通过http向其他web页面发出请求，并解析得到的文本， /// 以便提取数据。这称为屏幕抓取。 /// </summary> private void GetWebSite() { Uri uri = new Uri("http://www.google.com"); WebRequest request = HttpWebRequest.Create(uri); request.Method = WebRequestMethods.Http.Get; WebResponse response = request.GetResponse(); StreamReader sr = new StreamReader(response.GetResponseStream()); string temp = sr.ReadToEnd(); response.Close(); sr.Close(); this.panel1.GroupingText = temp; }

三、使用HttpWebRequest把数据传送给远程Web页面

private void PostDataToPage() { Uri uri = new Uri("http://www.amazon.com/Kirbys-Epic-Yarn-Nintendo-Wii/dp/B003ZCH7DI/ref=sr_1_1"); //Uri("http://www.amazon.com/exec/obidos/search-handle-form/102-5194535-6807312"); string data = "s=videogames&ie=UTF8&qid=1285484221&sr=1-1";//"field-keywords=Professional ASP.NET 3.5"; if (uri.Scheme == Uri.UriSchemeHttp) { HttpWebRequest request = HttpWebRequest.Create(uri) as HttpWebRequest; request.Method = WebRequestMethods.Http.Post; request.ContentLength = data.Length; request.ContentType = "application/x-www-form-urlencoded"; StreamWriter sw = new StreamWriter(request.GetRequestStream()); sw.Write(data); sw.Close(); HttpWebResponse response = request.GetResponse() as HttpWebResponse; StreamReader sr = new StreamReader(response.GetResponseStream()); string temp = sr.ReadToEnd(); sr.Close(); response.Close(); this.panel2.GroupingText = temp; } } //======================================== //异步操作（参考） public static ManualResetEvent allDone = new ManualResetEvent(false); const int BUFFER_SIZE = 1024; const int DefaultTimeout = 2 * 60 * 1000; // 2 minutes timeout // Abort the request if the timer fires. private static void TimeoutCallback(object state, bool timedOut) { if (timedOut) { HttpWebRequest request = state as HttpWebRequest; if (request != null) { request.Abort(); } } } private void PostDataToPageAsyc(){ Uri uri = new Uri("http://www.amazon.com/Kirbys-Epic-Yarn-Nintendo-Wii/dp/B003ZCH7DI/ref=sr_1_1"); //Uri("http://www.amazon.com/exec/obidos/search-handle-form/102-5194535-6807312"); string data = "s=videogames&ie=UTF8&qid=1285484221&sr=1-1";//"field-keywords=Professional ASP.NET 3.5"; if (uri.Scheme == Uri.UriSchemeHttp) { try { HttpWebRequest request = HttpWebRequest.Create(uri) as HttpWebRequest; request.Method = WebRequestMethods.Http.Post; request.ContentLength = data.Length; request.ContentType = "application/x-www-form-urlencoded"; StreamWriter sw = new StreamWriter(request.GetRequestStream()); sw.Write(data); sw.Close(); //request.BeginGetResponse(GetRequestAsync, request); RequestState myRequestState = new RequestState(); myRequestState.request = request; //start asynchronous request IAsyncResult result = request.BeginGetResponse(new AsyncCallback(ResponseCallBack), myRequestState); // this line implements the timeout, if there is a timeout, the callback fires and the request becomes aborted ThreadPool.RegisterWaitForSingleObject(result.AsyncWaitHandle, new WaitOrTimerCallback(TimeoutCallback), request, DefaultTimeout, true); // The response came in the allowed time. The work processing will happen in the // callback function. allDone.WaitOne(); // Release the HttpWebResponse resource. myRequestState.response.Close(); } catch (WebException e) { Response.Write(e.Message); } //HttpWebResponse response = request.GetResponse() as HttpWebResponse; //StreamReader sr = new StreamReader(response.GetResponseStream()); //string temp = sr.ReadToEnd(); //response.Close(); //sr.Close(); //this.panel2.GroupingText = temp; } } private void ResponseCallBack(IAsyncResult asynchronousResult) { //state of request is asynchronous RequestState myRequestState = asynchronousResult.AsyncState as RequestState; HttpWebRequest request = myRequestState.request; myRequestState.response = request.EndGetResponse(asynchronousResult) as HttpWebResponse; //read thr response into a stream object Stream responseStream = myRequestState.response.GetResponseStream(); myRequestState.streamResponse = responseStream; //begin the reading of thr contents of the html page and print it to string IAsyncResult asynchronousInputRead = responseStream.BeginRead(myRequestState.BufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadHtmlCallBack), myRequestState); return; } private void ReadHtmlCallBack(IAsyncResult asynchronousResult) { try { //state of request is asynchronous RequestState myRequestState = asynchronousResult.AsyncState as RequestState; Stream responseStream = myRequestState.streamResponse; int read = responseStream.EndRead(asynchronousResult); if (read > 0) { string temp = System.Text.Encoding.ASCII.GetString(myRequestState.BufferRead, 0, BUFFER_SIZE); myRequestState.requestData.Append(temp); IAsyncResult myAsynchronousResult = responseStream.BeginRead(myRequestState.BufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadHtmlCallBack), myRequestState); return; } else { if (myRequestState.requestData.Length > 1) { this.panel2.GroupingText += myRequestState.requestData.ToString(); } } } catch (WebException ex) { Response.Write(ex.Message); } } public class RequestState { // This class stores the State of the request. const int BUFFER_SIZE = 1024; public StringBuilder requestData; public byte[] BufferRead; public HttpWebRequest request; public HttpWebResponse response; public Stream streamResponse; public RequestState() { BufferRead = new byte[BUFFER_SIZE]; requestData = new StringBuilder(""); request = null; streamResponse = null; } }