Begins an asynchronous request to an Internet resource.
Assembly: System (in System.dll)
[<HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)>] abstract BeginGetResponse : callback:AsyncCallback * state:Object -> IAsyncResult [<HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)>] override BeginGetResponse : callback:AsyncCallback * state:Object -> IAsyncResult
- Type: System.Object
The state object for this request.
The stream is already in use by a previous call to
The thread pool is running out of threads.
The ContentLength is greater than zero, but the application does not write all of the promised data.
Abort was previously called.
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).
The 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 some time, typically several seconds. In some environments where the webproxy scripts are not configured properly, this can take 60 seconds or more. The default value for the downloadTime attribute on the <webProxyScipt> config file element is one minute which accounts for most of the potential time delay.
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 method to retrieve the response.
This member outputs trace information when you enable network tracing in your application. For more information, see Network Tracing.
The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: ExternalThreading. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.
The following code example uses the 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.
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.