UploadFileAsync Method (Uri, String)

WebClient.UploadFileAsync Method (Uri, String)


Uploads the specified local file to the specified resource, using the POST method. This method does not block the calling thread.

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

[HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)]
public void UploadFileAsync(
	Uri address,
	string fileName


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.

Type: System.String

The file to send to the resource.

Exception Condition

The address parameter is null.


The fileName parameter is null.


The URI formed by combining BaseAddress and address is invalid.


fileName is null, is Empty, contains invalid character, or the specified path to the file does not exist.


An error occurred while opening the stream.


There was no response from the server hosting the resource.


The Content-type header begins with multipart.

The file is sent asynchronously using thread resources that are automatically allocated from the thread pool. To receive notification when the file upload completes, add an event handler to the UploadFileCompleted event.

This method does not block the calling thread while the file is being sent. To send a file and block while waiting for the server's response, use one of the UploadFile methods.

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

If the BaseAddress property is not an empty string (""), 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.

This method uses the STOR command to upload an FTP resource. For an HTTP resource, the POST method is used.


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


to access the local file. Associated enumeration: Read.

.NET Framework
Available since 2.0
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