WebClient.DownloadDataAsync Method

Definition

Namespace:

System.Net

Assembly:

System.Net.WebClient.dll

Downloads the resource as a Byte array from the URI specified as an asynchronous operation. These methods do not block the calling thread.

Overloads

DownloadDataAsync(Uri)	Downloads the resource as a Byte array from the URI specified as an asynchronous operation.
DownloadDataAsync(Uri, Object)	Downloads the resource as a Byte array from the URI specified as an asynchronous operation.

DownloadDataAsync(Uri)

Source:

WebClient.cs

Downloads the resource as a Byte array from the URI specified as an asynchronous operation.

public:
 void DownloadDataAsync(Uri ^ address);

public void DownloadDataAsync (Uri address);

member this.DownloadDataAsync : Uri -> unit

Public Sub DownloadDataAsync (address As Uri)

Parameters

address

Uri

A Uri containing the URI to download.

Exceptions

ArgumentNullException

The address parameter is null.

WebException

The URI formed by combining BaseAddress and address is invalid.

-or-

An error occurred while downloading the resource.

Remarks

Caution

WebRequest, HttpWebRequest, ServicePoint, and WebClient are obsolete, and you shouldn't use them for new development. Use HttpClient instead.

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.

In .NET Framework and .NET Core 1.0, you can cancel asynchronous operations that have not completed by calling the CancelAsync method.

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.

Note

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

This method stores in the task it returns all non-usage exceptions that the method's synchronous counterpart can throw. If an exception is stored into the returned task, that exception will be thrown when the task is awaited. Usage exceptions, such as ArgumentException, are still thrown synchronously. For the stored exceptions, see the exceptions thrown by DownloadData(Uri).

DownloadDataAsync(Uri, Object)

Source:

WebClient.cs

Downloads the resource as a Byte array from the URI specified as an asynchronous operation.

public:
 void DownloadDataAsync(Uri ^ address, System::Object ^ userToken);

public void DownloadDataAsync (Uri address, object? userToken);

member this.DownloadDataAsync : Uri * obj -> unit

Public Sub DownloadDataAsync (address As Uri, userToken As Object)

Parameters

address

Uri

A Uri containing the URI to download.

userToken

Object

A user-defined object that is passed to the method invoked when the asynchronous operation completes.

Exceptions

ArgumentNullException

The address parameter is null.

WebException

The URI formed by combining BaseAddress and address is invalid.

-or-

An error occurred while downloading the resource.

Remarks

Caution

WebRequest, HttpWebRequest, ServicePoint, and WebClient are obsolete, and you shouldn't use them for new development. Use HttpClient instead.

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.

In .NET Framework and .NET Core 1.0, you can cancel asynchronous operations that have not completed by calling the CancelAsync method.

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.

Note

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