WebClient.OnDownloadProgressChanged(DownloadProgressChangedEventArgs) 方法

定义

引发 DownloadProgressChanged 事件。Raises the DownloadProgressChanged event.

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

e
DownloadProgressChangedEventArgs

包含事件数据的 DownloadProgressChangedEventArgs 对象。A DownloadProgressChangedEventArgs object containing event data.

示例

下面的代码示例演示了此方法的一个实现,该实现可由派生自的类进行自定义 WebClientThe following code example shows an implementation of this method that can be customized by a class derived from WebClient.

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

从此类继承的类可以重写此方法,以便在事件发生时执行其他任务 DownloadProgressChangedClasses that inherit from this class can override this method to perform additional tasks when the DownloadProgressChanged event occurs.

引发事件时,将通过委托调用事件处理程序。Raising an event invokes the event handler through a delegate. 有关详细信息,请参阅 处理和引发事件For more information, see Handling and Raising Events.

OnDownloadProgressChanged 方法还允许派生类对事件进行处理而不必附加委托。The OnDownloadProgressChanged method also allows derived classes to handle the event without attaching a delegate. 这是在派生类中处理事件的首选技术。This is the preferred technique for handling the event in a derived class.

继承者说明

OnDownloadProgressChanged(DownloadProgressChangedEventArgs) 在派生类中重写时,请确保调用基类的 OnDownloadProgressChanged(DownloadProgressChangedEventArgs) 方法,以便注册的委托接收事件。When overriding OnDownloadProgressChanged(DownloadProgressChangedEventArgs) in a derived class, be sure to call the base class' OnDownloadProgressChanged(DownloadProgressChangedEventArgs) method so that registered delegates receive the event.

适用于