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WebClient.DownloadProgressChanged Event

Occurs when an asynchronous download operation successfully transfers some or all of the data.

Namespace:  System.Net
Assembly:  System (in System.dll)
public event DownloadProgressChangedEventHandler DownloadProgressChanged

This event is raised each time an asynchronous download makes progress. This event is raised when downloads are started using any of the following methods.

Method

Description

DownloadDataAsync

Downloads data from a resource and returns a Byte array, without blocking the calling thread.

DownloadFileAsync

Downloads data from a resource to a local file, without blocking the calling thread.

OpenReadAsync

Returns the data from a resource, without blocking the calling thread.

The DownloadProgressChangedEventHandler is the delegate for this event. The DownloadProgressChangedEventArgs class provides the event handler with event data.

For more information about handling events, see Consuming Events.

NoteNote

A passive FTP file transfer will always show a progress percentage of zero, since the server did not send the file size. To show progress, you can change the FTP connection to active by overriding the GetWebRequest virtual method:

internal class MyWebClient:WebClient{
        protected override WebRequest GetWebRequest(Uri address) {
            FtpWebRequest req = (FtpWebRequest)base.GetWebRequest(address);
            req.UsePassive = false;
            return req;
        }
    }

The following code example demonstrates setting an event handler for this event.


    // Sample call : DownLoadFileInBackground2 ("http://www.contoso.com/logs/January.txt");
    public static void DownLoadFileInBackground2 (string address)
    {
        WebClient client = new WebClient ();
        Uri uri = new Uri(address);

        // Specify that the DownloadFileCallback method gets called
        // when the download completes.
        client.DownloadFileCompleted += new AsyncCompletedEventHandler (DownloadFileCallback2);
        // Specify a progress notification handler.
        client.DownloadProgressChanged += new DownloadProgressChangedEventHandler(DownloadProgressCallback);
        client.DownloadFileAsync (uri, "serverdata.txt");
    }



The following code example shows an implementation of a handler for this event.


private static void UploadProgressCallback(object sender, UploadProgressChangedEventArgs e)
{
    // Displays the operation identifier, and the transfer progress.
    Console.WriteLine("{0}    uploaded {1} of {2} bytes. {3} % complete...", 
        (string)e.UserState, 
        e.BytesSent, 
        e.TotalBytesToSend,
        e.ProgressPercentage);
}
private static void DownloadProgressCallback(object sender, DownloadProgressChangedEventArgs e)
{
    // Displays the operation identifier, and the transfer progress.
    Console.WriteLine("{0}    downloaded {1} of {2} bytes. {3} % complete...", 
        (string)e.UserState, 
        e.BytesReceived, 
        e.TotalBytesToReceive,
        e.ProgressPercentage);
}


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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