WebClient.OpenWriteAsync Method (Uri, String, Object)

Microsoft Silverlight will reach end of support after October 2021. Learn more.

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.Net (in System.Net.dll)


Public Sub OpenWriteAsync ( _
    address As Uri, _
    method As String, _
    userToken As Object _
public void OpenWriteAsync(
    Uri address,
    string method,
    Object userToken


  • 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.
  • userToken
    Type: System.Object
    A user-defined object that is passed to the method invoked when the asynchronous operation completes


Exception Condition

The address parameter is nulla null reference (Nothing in Visual Basic).


There is not enough memory to continue the execution of the program.


The execution stack overflowed because it contains too many nested method calls.


A call was made to the Thread.Abort method to destroy a thread.


The URI formed by combining BaseAddress and address is invalid.


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.

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.

Version Information


Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Windows Phone OS 7.0


For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.