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WebClient.OpenWriteAsync Method (Uri, String, Object)

Opens a stream for writing data to the specified resource, using the specified method. This method does not block the calling thread.

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

[HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)]
public void OpenWriteAsync(
	Uri address,
	string method,
	Object userToken
)

Parameters

address
Type: System.Uri

The URI of the resource to receive the data.

method
Type: System.String

The method used to send the data to the resource. If null, the default is POST for http and STOR for ftp.

userToken
Type: System.Object

A user-defined object that is passed to the method invoked when the asynchronous operation completes

ExceptionCondition
ArgumentNullException

The address parameter is null.

WebException

The URI formed by combining BaseAddress and address is invalid.

-or-

An error occurred while opening the stream.

This method retrieves a writable stream that is used to send data to a resource. The stream is retrieved asynchronously using thread resources that are automatically allocated from the thread pool. To receive notification when the stream is available, add an event handler to the OpenWriteCompleted event. The contents of the stream are sent to the server when you close the stream.

If the method parameter specifies a method that is not understood by the server, the underlying protocol classes determine what occurs. Typically, a WebException is thrown with the Status property set to indicate the error.

Asynchronous operations that have not completed can be canceled using the CancelAsync method.

This method does not block the calling thread while the stream is being opened. To block while waiting for the stream, use one of the OpenWrite methods.

If the BaseAddress property is not an empty string ("") and address does not contain an absolute URI, address must be a relative URI that is combined with BaseAddress to form the absolute URI of the requested data. If the QueryString property is not an empty string, it is appended to address.

NoteNote

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

NoteNote

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.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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