WebClient.UploadStringAsync Method (Uri, String, String, Object)

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Uploads the specified string to the specified resource. This method does not block the calling thread.

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


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


  • address
    Type: System..::.Uri
    The URI of the resource to receive the file. For HTTP resources, this URI must identify a resource that can accept a request sent with the POST method, such as a script or ASP page.
  • method
    Type: System..::.String
    The HTTP method used to send the file 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 nullNothingnullptra null reference (Nothing in Visual Basic)


data is nullNothingnullptra 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.


There was no response from the server hosting the resource.


This method sends a string to a resource. The string is sent asynchronously using thread resources that are automatically allocated from the thread pool. Before uploading the string, this method converts it to a Byte array using the encoding specified in the Encoding property. To receive notification when the string upload completes, you can add an event handler to the UploadStringCompleted event.

This method does not block the calling thread while the string is being sent.

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

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

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0


Windows Phone

See Also


WebClient Class

UploadStringAsync Overload

System.Net Namespace