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DownloadDataCompletedEventHandler Delegate

Represents the method that will handle the DownloadDataCompleted event of a WebClient.

Namespace:  System.Net
Assembly:  System (in System.dll)
public delegate void DownloadDataCompletedEventHandler(
	Object sender,
	DownloadDataCompletedEventArgs e
)

Parameters

sender
Type: System.Object

The source of the event.

e
Type: System.Net.DownloadDataCompletedEventArgs

A DownloadDataCompletedEventArgs containing event data.

When you create a DownloadDataCompletedEventHandler delegate, you identify the method that will handle the event. To associate the event with your event handler, add an instance of the delegate to the event. The event handler is called whenever the event occurs, unless you remove the delegate. For more information about event handler delegates, see Events and Delegates.

The following code example demonstrates downloading a user-specified resource.

// Sample call : DownLoadDataInBackground ("http://www.contoso.com/GameScores.html");
public static void DownloadDataInBackground (string address)
{
    System.Threading.AutoResetEvent waiter = new System.Threading.AutoResetEvent (false);
    WebClient client = new WebClient ();
    Uri uri = new Uri(address);

    // Specify that the DownloadDataCallback method gets called 
    // when the download completes.
    client.DownloadDataCompleted += new DownloadDataCompletedEventHandler (DownloadDataCallback);
    client.DownloadDataAsync (uri, waiter);

    // Block the main application thread. Real applications 
    // can perform other tasks while waiting for the download to complete.
    waiter.WaitOne ();
}
// Sample call : DownLoadDataInBackground ("http://www.contoso.com/GameScores.html");
void DownloadDataInBackground (String* address)
{
    System::Threading::AutoResetEvent* waiter = new System::Threading::AutoResetEvent (false);
    WebClient* client = new WebClient ();

    // Specify that the DownloadDataCallback method gets called
    // when the download completes.
    client->DownloadDataCompleted += new DownloadDataCompletedEventHandler (DownloadDataCallback);
    client->DownloadDataAsync (address, waiter);

    // Block the main application thread. Real applications
    // can perform other tasks while waiting for the download to complete.
    waiter->WaitOne ();
}

The following method is called when the download completes.

private static void DownloadDataCallback (Object sender, DownloadDataCompletedEventArgs e)
{
    System.Threading.AutoResetEvent waiter = (System.Threading.AutoResetEvent)e.UserState;

    try
    {
        // If the request was not canceled and did not throw 
        // an exception, display the resource. 
        if (!e.Cancelled && e.Error == null)
        {
            byte[] data = (byte[])e.Result;
            string textData = System.Text.Encoding.UTF8.GetString (data);

            Console.WriteLine (textData);
        }
    }
    finally
    {
        // Let the main application thread resume.
        waiter.Set ();
    }
}
void DownloadDataCallback (Object* /*sender*/, DownloadDataCompletedEventArgs* e)
{
    System::Threading::AutoResetEvent* waiter = dynamic_cast<System::Threading::AutoResetEvent*>(e->UserToken);

    try
    {
        // If the request was not canceled and did not throw
        // an exception, display the resource.
        if (!e->Cancelled && e->Error == 0)
        {
            Byte data[] = dynamic_cast<Byte[]>(e->Result);
            String* textData = System::Text::Encoding::UTF8->GetString (data);

            Console::WriteLine (textData);
        }
    }
    __finally
    {
        // Let the main application thread resume.
        waiter->Set ();
    }
}

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0
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