HttpWebRequest.BeginGetResponse(AsyncCallback, Object) Método
Definición
Importante
Parte de la información hace referencia a la versión preliminar del producto, que puede haberse modificado sustancialmente antes de lanzar la versión definitiva. Microsoft no otorga ninguna garantía, explícita o implícita, con respecto a la información proporcionada aquí.
Inicia una solicitud asincrónica de un recurso de Internet.
public:
override IAsyncResult ^ BeginGetResponse(AsyncCallback ^ callback, System::Object ^ state);public override IAsyncResult BeginGetResponse (AsyncCallback callback, object state);public override IAsyncResult BeginGetResponse (AsyncCallback? callback, object? state);override this.BeginGetResponse : AsyncCallback * obj -> IAsyncResultPublic Overrides Function BeginGetResponse (callback As AsyncCallback, state As Object) As IAsyncResultParámetros
- callback
- AsyncCallback
Delegado AsyncCallback.
- state
- Object
Objeto de estado de esta solicitud.
Devoluciones
IAsyncResult que hace referencia a la solicitud asincrónica de una respuesta.
Excepciones
La secuencia ya la está usando una llamada anterior a BeginGetResponse(AsyncCallback, Object).
o bien
TransferEncoding se establece en un valor y SendChunked es false.
o bien
El grupo de subprocesos se está quedando sin subprocesos.
Method es GET o HEAD y ContentLength es mayor o igual que cero o SendChunked es true.
o bien
KeepAlive es true, AllowWriteStreamBuffering es false y ContentLength es -1, SendChunked es false y Method es POST o PUT.
o bien
La HttpWebRequest tiene un cuerpo de entidad, pero el método BeginGetResponse(AsyncCallback, Object) se invoca sin llamar al método BeginGetRequestStream(AsyncCallback, Object).
o bien
ContentLength es mayor que cero, pero la aplicación no escribe todos los datos prometidos.
Se llamó a Abort() anteriormente.
Ejemplos
En el ejemplo de código siguiente se usa el BeginGetResponse método para realizar una solicitud asincrónica para un recurso de Internet.
Nota:
En el caso de solicitudes asincrónicas, es responsabilidad de la aplicación cliente implementar su propio mecanismo de tiempo de espera. En el ejemplo de código siguiente se muestra cómo hacerlo.
#using <System.dll>
using namespace System;
using namespace System::Net;
using namespace System::IO;
using namespace System::Text;
using namespace System::Threading;
public ref class RequestState
{
private:
// This class stores the State of the request.
const int BUFFER_SIZE;
public:
StringBuilder^ requestData;
array<Byte>^BufferRead;
HttpWebRequest^ request;
HttpWebResponse^ response;
Stream^ streamResponse;
RequestState()
: BUFFER_SIZE( 1024 )
{
BufferRead = gcnew array<Byte>(BUFFER_SIZE);
requestData = gcnew StringBuilder( "" );
request = nullptr;
streamResponse = nullptr;
}
};
ref class HttpWebRequest_BeginGetResponse
{
public:
static ManualResetEvent^ allDone = gcnew ManualResetEvent( false );
literal int BUFFER_SIZE = 1024;
literal int DefaultTimeOut = 120000; // 2 minute timeout
// Abort the request if the timer fires.
static void TimeoutCallback( Object^ state, bool timedOut )
{
if ( timedOut )
{
HttpWebRequest^ request = dynamic_cast<HttpWebRequest^>(state);
if ( request != nullptr )
{
request->Abort();
}
}
}
static void RespCallback( IAsyncResult^ asynchronousResult )
{
try
{
// State of request is asynchronous.
RequestState^ myRequestState = dynamic_cast<RequestState^>(asynchronousResult->AsyncState);
HttpWebRequest^ myHttpWebRequest = myRequestState->request;
myRequestState->response = dynamic_cast<HttpWebResponse^>(myHttpWebRequest->EndGetResponse( asynchronousResult ));
// Read the response into a Stream object.
Stream^ responseStream = myRequestState->response->GetResponseStream();
myRequestState->streamResponse = responseStream;
// Begin the Reading of the contents of the HTML page and print it to the console.
IAsyncResult^ asynchronousInputRead = responseStream->BeginRead( myRequestState->BufferRead, 0, BUFFER_SIZE, gcnew AsyncCallback( ReadCallBack ), myRequestState );
return;
}
catch ( WebException^ e )
{
Console::WriteLine( "\nRespCallback Exception raised!" );
Console::WriteLine( "\nMessage: {0}", e->Message );
Console::WriteLine( "\nStatus: {0}", e->Status );
}
allDone->Set();
}
static void ReadCallBack( IAsyncResult^ asyncResult )
{
try
{
RequestState^ myRequestState = dynamic_cast<RequestState^>(asyncResult->AsyncState);
Stream^ responseStream = myRequestState->streamResponse;
int read = responseStream->EndRead( asyncResult );
// Read the HTML page and then print it to the console.
if ( read > 0 )
{
myRequestState->requestData->Append( Encoding::ASCII->GetString( myRequestState->BufferRead, 0, read ) );
IAsyncResult^ asynchronousResult = responseStream->BeginRead( myRequestState->BufferRead, 0, BUFFER_SIZE, gcnew AsyncCallback( ReadCallBack ), myRequestState );
return;
}
else
{
Console::WriteLine( "\nThe contents of the Html page are : " );
if ( myRequestState->requestData->Length > 1 )
{
String^ stringContent;
stringContent = myRequestState->requestData->ToString();
Console::WriteLine( stringContent );
}
Console::WriteLine( "Press any key to continue.........." );
Console::ReadLine();
responseStream->Close();
}
}
catch ( WebException^ e )
{
Console::WriteLine( "\nReadCallBack Exception raised!" );
Console::WriteLine( "\nMessage: {0}", e->Message );
Console::WriteLine( "\nStatus: {0}", e->Status );
}
allDone->Set();
}
};
int main()
{
try
{
// Create a HttpWebrequest object to the desired URL.
HttpWebRequest^ myHttpWebRequest = dynamic_cast<HttpWebRequest^>(WebRequest::Create( "http://www.contoso.com" ));
/**
* If you are behind a firewall and you do not have your browser proxy setup
* you need to use the following proxy creation code.
// Create a proxy object.
WebProxy* myProxy = new WebProxy();
// Associate a new Uri object to the _wProxy object, using the proxy address
// selected by the user.
myProxy.Address = new Uri(S"http://myproxy");
// Finally, initialize the Web request object proxy property with the _wProxy
// object.
myHttpWebRequest.Proxy=myProxy;
***/
// Create an instance of the RequestState and assign the previous myHttpWebRequest
// object to its request field.
RequestState^ myRequestState = gcnew RequestState;
myRequestState->request = myHttpWebRequest;
// Start the asynchronous request.
IAsyncResult^ result = dynamic_cast<IAsyncResult^>(myHttpWebRequest->BeginGetResponse( gcnew AsyncCallback( HttpWebRequest_BeginGetResponse::RespCallback ), myRequestState ));
// this line impliments the timeout, if there is a timeout, the callback fires and the request becomes aborted
ThreadPool::RegisterWaitForSingleObject( result->AsyncWaitHandle, gcnew WaitOrTimerCallback( HttpWebRequest_BeginGetResponse::TimeoutCallback ), myHttpWebRequest, HttpWebRequest_BeginGetResponse::DefaultTimeOut, true );
// The response came in the allowed time. The work processing will happen in the
// callback function.
HttpWebRequest_BeginGetResponse::allDone->WaitOne();
// Release the HttpWebResponse resource.
myRequestState->response->Close();
}
catch ( WebException^ e )
{
Console::WriteLine( "\nMain Exception raised!" );
Console::WriteLine( "\nMessage: {0}", e->Message );
Console::WriteLine( "\nStatus: {0}", e->Status );
Console::WriteLine( "Press any key to continue.........." );
}
catch ( Exception^ e )
{
Console::WriteLine( "\nMain Exception raised!" );
Console::WriteLine( "Source : {0} ", e->Source );
Console::WriteLine( "Message : {0} ", e->Message );
Console::WriteLine( "Press any key to continue.........." );
Console::Read();
}
}
using System;
using System.Net;
using System.IO;
using System.Text;
using System.Threading;
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;
}
}
class HttpWebRequest_BeginGetResponse
{
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();
}
}
}
static void Main()
{
try
{
// Create a HttpWebrequest object to the desired URL.
HttpWebRequest myHttpWebRequest= (HttpWebRequest)WebRequest.Create("http://www.contoso.com");
/**
* If you are behind a firewall and you do not have your browser proxy setup
* you need to use the following proxy creation code.
// Create a proxy object.
WebProxy myProxy = new WebProxy();
// Associate a new Uri object to the _wProxy object, using the proxy address
// selected by the user.
myProxy.Address = new Uri("http://myproxy");
// Finally, initialize the Web request object proxy property with the _wProxy
// object.
myHttpWebRequest.Proxy=myProxy;
***/
// Create an instance of the RequestState and assign the previous myHttpWebRequest
// object to its request field.
RequestState myRequestState = new RequestState();
myRequestState.request = myHttpWebRequest;
// Start the asynchronous request.
IAsyncResult result=
(IAsyncResult) myHttpWebRequest.BeginGetResponse(new AsyncCallback(RespCallback),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), myHttpWebRequest, 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)
{
Console.WriteLine("\nMain Exception raised!");
Console.WriteLine("\nMessage:{0}",e.Message);
Console.WriteLine("\nStatus:{0}",e.Status);
Console.WriteLine("Press any key to continue..........");
}
catch(Exception e)
{
Console.WriteLine("\nMain Exception raised!");
Console.WriteLine("Source :{0} " , e.Source);
Console.WriteLine("Message :{0} " , e.Message);
Console.WriteLine("Press any key to continue..........");
Console.Read();
}
}
private static void RespCallback(IAsyncResult asynchronousResult)
{
try
{
// State of request is asynchronous.
RequestState myRequestState=(RequestState) asynchronousResult.AsyncState;
HttpWebRequest myHttpWebRequest=myRequestState.request;
myRequestState.response = (HttpWebResponse) myHttpWebRequest.EndGetResponse(asynchronousResult);
// Read the response into a Stream object.
Stream responseStream = myRequestState.response.GetResponseStream();
myRequestState.streamResponse=responseStream;
// Begin the Reading of the contents of the HTML page and print it to the console.
IAsyncResult asynchronousInputRead = responseStream.BeginRead(myRequestState.BufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadCallBack), myRequestState);
return;
}
catch(WebException e)
{
Console.WriteLine("\nRespCallback Exception raised!");
Console.WriteLine("\nMessage:{0}",e.Message);
Console.WriteLine("\nStatus:{0}",e.Status);
}
allDone.Set();
}
private static void ReadCallBack(IAsyncResult asyncResult)
{
try
{
RequestState myRequestState = (RequestState)asyncResult.AsyncState;
Stream responseStream = myRequestState.streamResponse;
int read = responseStream.EndRead( asyncResult );
// Read the HTML page and then print it to the console.
if (read > 0)
{
myRequestState.requestData.Append(Encoding.ASCII.GetString(myRequestState.BufferRead, 0, read));
IAsyncResult asynchronousResult = responseStream.BeginRead( myRequestState.BufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadCallBack), myRequestState);
return;
}
else
{
Console.WriteLine("\nThe contents of the Html page are : ");
if(myRequestState.requestData.Length>1)
{
string stringContent;
stringContent = myRequestState.requestData.ToString();
Console.WriteLine(stringContent);
}
Console.WriteLine("Press any key to continue..........");
Console.ReadLine();
responseStream.Close();
}
}
catch(WebException e)
{
Console.WriteLine("\nReadCallBack Exception raised!");
Console.WriteLine("\nMessage:{0}",e.Message);
Console.WriteLine("\nStatus:{0}",e.Status);
}
allDone.Set();
}
Imports System.Net
Imports System.IO
Imports System.Text
Imports System.Threading
Public Class RequestState
' This class stores the State of the request.
Private BUFFER_SIZE As Integer = 1024
Public requestData As StringBuilder
Public BufferRead() As Byte
Public request As HttpWebRequest
Public response As HttpWebResponse
Public streamResponse As Stream
Public Sub New()
BufferRead = New Byte(BUFFER_SIZE) {}
requestData = New StringBuilder("")
request = Nothing
streamResponse = Nothing
End Sub
End Class
Class HttpWebRequest_BeginGetResponse
Public Shared allDone As New ManualResetEvent(False)
Private BUFFER_SIZE As Integer = 1024
Private DefaultTimeout As Integer = 2 * 60 * 1000
' 2 minutes timeout
' Abort the request if the timer fires.
Private Shared Sub TimeoutCallback(state As Object, timedOut As Boolean)
If timedOut Then
Dim request As HttpWebRequest = state
If Not (request Is Nothing) Then
request.Abort()
End If
End If
End Sub
Shared Sub Main()
Try
' Create a HttpWebrequest object to the desired URL.
Dim myHttpWebRequest As HttpWebRequest = WebRequest.Create("http://www.contoso.com")
' Create an instance of the RequestState and assign the previous myHttpWebRequest
' object to its request field.
Dim myRequestState As New RequestState()
myRequestState.request = myHttpWebRequest
Dim myResponse As New HttpWebRequest_BeginGetResponse()
' Start the asynchronous request.
Dim result As IAsyncResult = CType(myHttpWebRequest.BeginGetResponse(New AsyncCallback(AddressOf RespCallback), myRequestState), IAsyncResult)
' this line implements the timeout, if there is a timeout, the callback fires and the request aborts.
ThreadPool.RegisterWaitForSingleObject(result.AsyncWaitHandle, New WaitOrTimerCallback(AddressOf TimeoutCallback), myHttpWebRequest, myResponse.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 e As WebException
Console.WriteLine(ControlChars.Lf + "Main Exception raised!")
Console.WriteLine(ControlChars.Lf + "Message:{0}", e.Message)
Console.WriteLine(ControlChars.Lf + "Status:{0}", e.Status)
Console.WriteLine("Press any key to continue..........")
Catch e As Exception
Console.WriteLine(ControlChars.Lf + "Main Exception raised!")
Console.WriteLine("Source :{0} ", e.Source)
Console.WriteLine("Message :{0} ", e.Message)
Console.WriteLine("Press any key to continue..........")
Console.Read()
End Try
End Sub
Private Shared Sub RespCallback(asynchronousResult As IAsyncResult)
Try
' State of request is asynchronous.
Dim myRequestState As RequestState = CType(asynchronousResult.AsyncState, RequestState)
Dim myHttpWebRequest As HttpWebRequest = myRequestState.request
myRequestState.response = CType(myHttpWebRequest.EndGetResponse(asynchronousResult), HttpWebResponse)
' Read the response into a Stream object.
Dim responseStream As Stream = myRequestState.response.GetResponseStream()
myRequestState.streamResponse = responseStream
' Begin the Reading of the contents of the HTML page and print it to the console.
Dim asynchronousInputRead As IAsyncResult = responseStream.BeginRead(myRequestState.BufferRead, 0, 1024, New AsyncCallback(AddressOf ReadCallBack), myRequestState)
Return
Catch e As WebException
Console.WriteLine(ControlChars.Lf + "RespCallback Exception raised!")
Console.WriteLine(ControlChars.Lf + "Message:{0}", e.Message)
Console.WriteLine(ControlChars.Lf + "Status:{0}", e.Status)
End Try
allDone.Set()
End Sub
Private Shared Sub ReadCallBack(asyncResult As IAsyncResult)
Try
Dim myRequestState As RequestState = CType(asyncResult.AsyncState, RequestState)
Dim responseStream As Stream = myRequestState.streamResponse
Dim read As Integer = responseStream.EndRead(asyncResult)
' Read the HTML page and then print it to the console.
If read > 0 Then
myRequestState.requestData.Append(Encoding.ASCII.GetString(myRequestState.BufferRead, 0, read))
Dim asynchronousResult As IAsyncResult = responseStream.BeginRead(myRequestState.BufferRead, 0, 1024, New AsyncCallback(AddressOf ReadCallBack), myRequestState)
Return
Else
Console.WriteLine(ControlChars.Lf + "The contents of the Html page are : ")
If myRequestState.requestData.Length > 1 Then
Dim stringContent As String
stringContent = myRequestState.requestData.ToString()
Console.WriteLine(stringContent)
End If
Console.WriteLine("Press any key to continue..........")
Console.ReadLine()
responseStream.Close()
End If
Catch e As WebException
Console.WriteLine(ControlChars.Lf + "ReadCallBack Exception raised!")
Console.WriteLine(ControlChars.Lf + "Message:{0}", e.Message)
Console.WriteLine(ControlChars.Lf + "Status:{0}", e.Status)
End Try
allDone.Set()
End Sub
End Class
Comentarios
El BeginGetResponse método inicia una solicitud asincrónica para una respuesta del recurso de Internet. El método de devolución de llamada asincrónica usa el EndGetResponse método para devolver el valor real WebResponse.
Se ProtocolViolationException produce una excepción en varios casos cuando las propiedades establecidas en la HttpWebRequest clase están en conflicto. Esta excepción se produce si una aplicación establece la ContentLength propiedad y la SendChunked propiedad trueen y, a continuación, envía una solicitud HTTP GET. Esta excepción se produce si una aplicación intenta enviar fragmentado a un servidor que solo admite el protocolo HTTP 1.0, donde no se admite. Esta excepción se produce si una aplicación intenta enviar datos sin establecer la ContentLength propiedad o SendChunked cuando false el almacenamiento en búfer está deshabilitado y en una conexión keepalive (la KeepAlive propiedad es true).
Si se produce una WebException excepción , use las Response propiedades y Status de la excepción para determinar la respuesta del servidor.
El BeginGetResponse método requiere algunas tareas de configuración sincrónicas para completarse (resolución DNS, detección de proxy y conexión de socket TCP, por ejemplo) antes de que este método se convierta en asincrónico. Como resultado, nunca se debe llamar a este método en un subproceso de interfaz de usuario (UI) porque puede tardar mucho tiempo (hasta varios minutos en función de la configuración de red) para completar las tareas de configuración sincrónica iniciales antes de que se produzca una excepción para un error o el método se realice correctamente.
Para más información sobre el grupo de subprocesos, consulte El grupo de subprocesos administrados.
Nota
La aplicación no puede mezclar métodos sincrónicos y asincrónicos para una solicitud determinada. Si llama al BeginGetRequestStream método , debe usar el BeginGetResponse método para recuperar la respuesta.
Nota
Este miembro genera información de seguimiento cuando se habilita el seguimiento de red en la aplicación. Para obtener más información, vea Seguimiento de red en .NET Framework.
Se aplica a
Consulte también
Comentarios
Próximamente: A lo largo de 2024 iremos eliminando gradualmente GitHub Issues como mecanismo de comentarios sobre el contenido y lo sustituiremos por un nuevo sistema de comentarios. Para más información, vea: https://aka.ms/ContentUserFeedback.
Enviar y ver comentarios de