HttpWebRequest.EndGetResponse 方法
结束对 Internet 资源的异步请求。
**命名空间:**System.Net
**程序集:**System（在 system.dll 中）
语法
声明
Public Overrides Function EndGetResponse ( _
asyncResult As IAsyncResult _
) As WebResponse
用法
Dim instance As HttpWebRequest
Dim asyncResult As IAsyncResult
Dim returnValue As WebResponse
returnValue = instance.EndGetResponse(asyncResult)
public override WebResponse EndGetResponse (
IAsyncResult asyncResult
)
public:
virtual WebResponse^ EndGetResponse (
IAsyncResult^ asyncResult
) override
public WebResponse EndGetResponse (
IAsyncResult asyncResult
)
public override function EndGetResponse (
asyncResult : IAsyncResult
) : WebResponse
参数
- asyncResult
挂起的对响应的请求。
返回值
包含来自 Internet 资源的响应的 WebResponse。
异常
| 异常类型 | 条件 |
|---|---|
asyncResult 为 空引用（在 Visual Basic 中为 Nothing）。 |
|
以前使用 asyncResult. 调用过此方法。 - 或 - ContentLength 属性大于 0，但是数据尚未写入请求流。 |
|
Abort 以前被调用过。 - 或 - 处理请求时发生错误。 |
|
当前实例没有从 BeginGetResponse 调用返回 asyncResult。 |
备注
EndGetResponse 方法完成对通过调用 BeginGetResponse 方法启动的 Internet 资源的异步请求。
警告
必须调用 Close 方法关闭该流并释放连接。如果未能做到这一点，可能导致应用程序用完连接。
提示
当在应用程序中启用网络跟踪功能后，此成员将输出跟踪信息。有关更多信息，请参见 网络跟踪。
示例
下面的代码示例使用 EndGetResponse 方法结束对 Internet 资源的异步请求。
Try
' Create a new HttpWebrequest object to the desired URL.
Dim myHttpWebRequest1 As HttpWebRequest = CType(WebRequest.Create("https://www.contoso.com"), HttpWebRequest)
' Create an instance of the RequestState and assign the previous myHttpWebRequest1
' object to it's request field.
Dim myRequestState As New RequestState()
myRequestState.request = myHttpWebRequest1
' Start the Asynchronous request.
Dim result As IAsyncResult = CType(myHttpWebRequest1.BeginGetResponse(AddressOf RespCallback, myRequestState), IAsyncResult)
allDone.WaitOne()
' Release the HttpWebResponse resource.
myRequestState.response.Close()
Catch e As WebException
Console.WriteLine(ControlChars.Cr + "Exception raised!")
Console.WriteLine(ControlChars.Cr + "Message:{0}", e.Message)
Console.WriteLine(ControlChars.Cr + "Status:{0}", e.Status)
Console.WriteLine("Press any key to continue..........")
Catch e As Exception
Console.WriteLine(ControlChars.Cr + "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 ' Main
Private Shared Sub RespCallback(asynchronousResult As IAsyncResult)
Try
' State of request is asynchronous.
Dim myRequestState As RequestState = CType(asynchronousResult.AsyncState, RequestState)
Dim myHttpWebRequest2 As HttpWebRequest = myRequestState.request
myRequestState.response = CType(myHttpWebRequest2.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, BUFFER_SIZE, AddressOf ReadCallBack, myRequestState)
Catch e As WebException
Console.WriteLine(ControlChars.Cr + "Exception raised!")
Console.WriteLine(ControlChars.Cr + "Message:{0}", e.Message)
Console.WriteLine(ControlChars.Cr + "Status:{0}", e.Status)
End Try
End Sub ' RespCallback
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, BUFFER_SIZE, AddressOf ReadCallBack, myRequestState)
Else
Console.WriteLine(ControlChars.Cr + "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()
allDone.Set()
End If
Catch e As WebException
Console.WriteLine(ControlChars.Cr + "Exception raised!")
Console.WriteLine(ControlChars.Cr + "Message:{0}", e.Message)
Console.WriteLine(ControlChars.Cr + "Status:{0}", e.Status)
End Try
End Sub ' ReadCallBack
try
{
// Create a HttpWebrequest object to the desired URL.
HttpWebRequest myHttpWebRequest1= (HttpWebRequest)WebRequest.Create("https://www.contoso.com");
// Create an instance of the RequestState and assign the previous myHttpWebRequest1
// object to it's request field.
RequestState myRequestState = new RequestState();
myRequestState.request = myHttpWebRequest1;
// Start the asynchronous request.
IAsyncResult result=
(IAsyncResult) myHttpWebRequest1.BeginGetResponse(new AsyncCallback(RespCallback),myRequestState);
allDone.WaitOne();
// Release the HttpWebResponse resource.
myRequestState.response.Close();
}
catch(WebException e)
{
Console.WriteLine("\nException 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("\nException 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 myHttpWebRequest2=myRequestState.request;
myRequestState.response = (HttpWebResponse) myHttpWebRequest2.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);
}
catch(WebException e)
{
Console.WriteLine("\nException raised!");
Console.WriteLine("\nMessage:{0}",e.Message);
Console.WriteLine("\nStatus:{0}",e.Status);
}
}
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);
}
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();
allDone.Set();
}
}
catch(WebException e)
{
Console.WriteLine("\nException raised!");
Console.WriteLine("\nMessage:{0}",e.Message);
Console.WriteLine("\nStatus:{0}",e.Status);
}
}
static void RespCallback( IAsyncResult^ asynchronousResult )
{
try
{
// State of request is asynchronous.
RequestState^ myRequestState = dynamic_cast<RequestState^>(asynchronousResult->AsyncState);
HttpWebRequest^ myHttpWebRequest2 = myRequestState->request;
myRequestState->response = dynamic_cast<HttpWebResponse^>(myHttpWebRequest2->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 );
}
catch ( WebException^ e )
{
Console::WriteLine( "\nException raised!" );
Console::WriteLine( "\nMessage: {0}", e->Message );
Console::WriteLine( "\nStatus: {0}", e->Status );
}
}
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 );
}
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();
allDone->Set();
}
}
catch ( WebException^ e )
{
Console::WriteLine( "\nException raised!" );
Console::WriteLine( "\nMessage: {0}", e->Message );
Console::WriteLine( "\nStatus: {0}", e->Status );
}
}
};
int main()
{
try
{
// Create a HttpWebrequest object to the desired URL.
HttpWebRequest^ myHttpWebRequest1 = dynamic_cast<HttpWebRequest^>(WebRequest::Create( "https://www.contoso.com" ));
// Create an instance of the RequestState and assign the previous myHttpWebRequest1
// object to its request field.
RequestState^ myRequestState = gcnew RequestState;
myRequestState->request = myHttpWebRequest1;
// Start the asynchronous request.
IAsyncResult^ result = dynamic_cast<IAsyncResult^>(myHttpWebRequest1->BeginGetResponse( gcnew AsyncCallback( HttpWebRequest_BeginGetResponse::RespCallback ), myRequestState ));
HttpWebRequest_BeginGetResponse::allDone->WaitOne();
// Release the HttpWebResponse resource.
myRequestState->response->Close();
}
catch ( WebException^ e )
{
Console::WriteLine( "\nException 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( "\nException raised!" );
Console::WriteLine( "Source : {0} ", e->Source );
Console::WriteLine( "Message : {0} ", e->Message );
Console::WriteLine( "Press any key to continue.........." );
Console::Read();
}
}
try {
// Create a HttpWebrequest object to the desired URL.
HttpWebRequest myHttpWebRequest1 = ((HttpWebRequest)
(WebRequest.Create("https://www.contoso.com")));
// Create an instance of the RequestState and assign the
//previous myHttpWebRequest1
// object to it's request field.
RequestState myRequestState = new RequestState();
myRequestState.request = myHttpWebRequest1;
// Start the asynchronous request.
IAsyncResult result = (IAsyncResult)
(myHttpWebRequest1.BeginGetResponse(new
AsyncCallback(RespCallback), myRequestState));
allDone.WaitOne();
// Release the HttpWebResponse resource.
myRequestState.response.Close();
}
catch (WebException e) {
Console.WriteLine("\nException raised!");
Console.WriteLine("\nMessage:{0}", e.get_Message());
Console.WriteLine("\nStatus:{0}", e.get_Status());
Console.WriteLine("Press any key to continue..........");
}
catch (System.Exception e) {
Console.WriteLine("\nException raised!");
Console.WriteLine("Source :{0} ", e.get_Source());
Console.WriteLine("Message :{0} ", e.get_Message());
Console.WriteLine("Press any key to continue..........");
Console.Read();
}
} //main
private static void RespCallback(IAsyncResult asynchronousResult)
{
try {
// State of request is asynchronous.
RequestState myRequestState = (RequestState)
(asynchronousResult.get_AsyncState());
HttpWebRequest myHttpWebRequest2 = myRequestState.request;
myRequestState.response = (HttpWebResponse)(myHttpWebRequest2.
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);
}
catch (WebException e) {
Console.WriteLine("\nException raised!");
Console.WriteLine("\nMessage:{0}", e.get_Message());
Console.WriteLine("\nStatus:{0}", e.get_Status());
}
} //RespCallback
private static void ReadCallBack(IAsyncResult asyncResult)
{
try {
RequestState myRequestState = (RequestState)
(asyncResult.get_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.get_ASCII().
GetString(myRequestState.bufferRead, 0, read));
IAsyncResult asynchronousResult = responseStream.BeginRead
(myRequestState.bufferRead, 0, BUFFER_SIZE, new
AsyncCallback(ReadCallBack), myRequestState);
}
else {
Console.WriteLine("\nThe contents of the Html page are : ");
if (myRequestState.requestData.get_Length() > 1) {
String stringContent;
stringContent = myRequestState.requestData.ToString();
Console.WriteLine(stringContent);
}
Console.WriteLine("Press any key to continue..........");
Console.ReadLine();
responseStream.Close();
allDone.Set();
}
}
catch (WebException e) {
Console.WriteLine("\nException raised!");
Console.WriteLine("\nMessage:{0}", e.get_Message());
Console.WriteLine("\nStatus:{0}", e.get_Status());
}
} //ReadCallBack
} //HttpWebRequest_BeginGetResponse
平台
Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition
.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。
版本信息
.NET Framework
受以下版本支持：2.0、1.1、1.0
.NET Compact Framework
受以下版本支持：2.0、1.0