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WebClient.UploadStringTaskAsync Method (String, String, String)

.NET Framework 4.5

Uploads the specified string to the specified resource as an asynchronous operation using a task object.

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

[<HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)>]
member UploadStringTaskAsync : 
        address:string * 
        method:string * 
        data:string -> Task<string> 


Type: System.String

The URI of the resource to receive the string. 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 HTTP method used to send the file to the resource. If null, the default is POST for http and STOR for ftp.

Type: System.String

The string to be uploaded.

Return Value

Type: System.Threading.Tasks.Task(String)
Returns Task(TResult).
The task object representing the asynchronous operation. The Result property on the task object returns a String containing the response sent by the server.


data is a null reference (Nothing in Visual Basic).


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


The data parameter is a null reference (Nothing in Visual Basic).


The URI formed by combining BaseAddress and address is invalid.


method cannot be used to send content.


There was no response from the server hosting the resource.

This operation will not block. The returned Task(TResult) object will complete after the string has been uploaded to the resource. The string is sent asynchronously using thread resources that are automatically allocated from the thread pool.

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

Before uploading the string, this method converts it to a Byte array using the encoding specified in the Encoding property. This method blocks while the string is transmitted.

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.


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


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
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