WebClient.DownloadDataAsync Method (Uri, Object)
Downloads the resource as a Byte array from the URI specified as an asynchronous operation.
Assembly: System (in System.dll)
[HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)] public void DownloadDataAsync( Uri address, Object userToken )
This method retrieves the specified resource using the default method for the protocol associated with the URI scheme specified in address. The data is downloaded asynchronously using thread resources that are automatically allocated from the thread pool.
This method does not block the calling thread while downloading the resource. To download a resource and block while waiting for the server's response, use one of the DownloadData methods. When the download completes, the DownloadDataCompleted event is raised. Your application must handle this event to receive notification. The downloaded data is available in the Result property.
You can use the CancelAsync method to cancel asynchronous operations that have not completed.
This method uses the RETR command to download an FTP resource. For an HTTP resource, the GET method is used.
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.