BeginGetResponse Method

HttpWebRequest.BeginGetResponse Method (AsyncCallback, Object)


Begins an asynchronous request to an Internet resource.

Namespace:   System.Net
Assembly:  System (in System.dll)

[<HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)>]
override BeginGetResponse : 
        callback:AsyncCallback *
        state:Object -> IAsyncResult


Type: System.AsyncCallback

The AsyncCallback delegate

Type: System.Object

The state object for this request.

Return Value

Type: System.IAsyncResult

An IAsyncResult that references the asynchronous request for a response.

Exception Condition

The stream is already in use by a previous call to BeginGetResponse


TransferEncoding is set to a value and SendChunked is false.


The thread pool is running out of threads.


Method is GET or HEAD, and either ContentLength is greater than zero or SendChunked is true.


KeepAlive is true, AllowWriteStreamBuffering is false, and either ContentLength is -1, SendChunked is false and Method is POST or PUT.


The HttpWebRequest has an entity body but the BeginGetResponse method is called without calling the BeginGetRequestStream method.


The ContentLength is greater than zero, but the application does not write all of the promised data.


Abort was previously called.

The BeginGetResponse method starts an asynchronous request for a response from the Internet resource. The asynchronous callback method uses the EndGetResponse method to return the actual WebResponse.

A ProtocolViolationException is thrown in several cases when the properties set on the HttpWebRequest class are conflicting. This exception occurs if an application sets the ContentLength property and the SendChunked property to true, and then sends an HTTP GET request. This exception occurs if an application tries to send chunked to a server that only supports HTTP 1.0 protocol, where this is not supported. This exception occurs if an application tries to send data without setting the ContentLength property or the SendChunked is false when buffering is disabled and on a keepalive connection (the KeepAlive property is true).

If a WebException is thrown, use the Response and Status properties of the exception to determine the response from the server.

The BeginGetResponse method requires some synchronous setup tasks to complete (DNS resolution, proxy detection, and TCP socket connection, for example) before this method becomes asynchronous. As a result, this method should never be called on a user interface (UI) thread because it might take considerable time (up to several minutes depending on network settings) to complete the initial synchronous setup tasks before an exception for an error is thrown or the method succeeds.

To learn more about the thread pool, see The Managed Thread Pool.


Your application cannot mix synchronous and asynchronous methods for a particular request. If you call the BeginGetRequestStream method, you must use the BeginGetResponse method to retrieve the response.


This member outputs trace information when you enable network tracing in your application. For more information, see Network Tracing in the .NET Framework.

The following code example uses the BeginGetResponse method to make an asynchronous request for an Internet resource.


In the case of asynchronous requests, it is the responsibility of the client application to implement its own time-out mechanism. The following code example shows how to do it.

No code example is currently available or this language may not be supported.

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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