WebClient.OnDownloadProgressChanged(DownloadProgressChangedEventArgs) 方法

定义

引发 DownloadProgressChanged 事件。

protected:
 virtual void OnDownloadProgressChanged(System::Net::DownloadProgressChangedEventArgs ^ e);
protected virtual void OnDownloadProgressChanged (System.Net.DownloadProgressChangedEventArgs e);
abstract member OnDownloadProgressChanged : System.Net.DownloadProgressChangedEventArgs -> unit
override this.OnDownloadProgressChanged : System.Net.DownloadProgressChangedEventArgs -> unit
Protected Overridable Sub OnDownloadProgressChanged (e As DownloadProgressChangedEventArgs)

参数

示例

下面的代码示例演示此方法的实现,该方法可由派生自 WebClient的类进行自定义。

virtual void OnDownloadProgressChanged( DownloadProgressChangedEventArgs ^ e ) override
{
   // Here you can perform any custom actions before the event is raised
   // and event handlers are called...
   WebClient::OnDownloadProgressChanged( e );

   // Here you can perform any post event actions...
}
protected override void OnDownloadProgressChanged (DownloadProgressChangedEventArgs e)
{
    // Here you can perform any custom actions before the event is raised
    // and event handlers are called...

    base.OnDownloadProgressChanged (e);

    // Here you can perform any post event actions...
}

注解

谨慎

WebRequestHttpWebRequestServicePointWebClient 已过时,不应将其用于新开发。 请改用 HttpClient

从此类继承的类可以重写此方法,以在发生 DownloadProgressChanged 事件时执行其他任务。

引发事件会通过委托调用事件处理程序。 有关详细信息,请参阅 处理和引发事件

OnDownloadProgressChanged 方法还允许派生类在不附加委托的情况下处理事件。 这是处理派生类中的事件的首选技术。

继承者说明

在派生类中重写 OnDownloadProgressChanged(DownloadProgressChangedEventArgs) 时,请务必调用基类的 OnDownloadProgressChanged(DownloadProgressChangedEventArgs) 方法,以便注册的委托接收事件。

适用于