Assembly: System (in System.dll)
type DownloadProgressChangedEventHandler = delegate of sender:Object * e:DownloadProgressChangedEventArgs -> unit
When you create a 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. Events and Delegates
If the server does not send the size of the downloaded file (such as in the case of a passive FTP connection), ProgressPercentage may always be zero.