未调用 DownloadFileCompleted 事件

Question

我正在尝试从服务器下载文件，但未调用 "DownloadFileCompleted" 事件。有人知道为什么吗？

来源：

Public Event DownloadFileCompleted As AsyncCompletedEventHandler

Public Sub DownloadCompleted(sender As Object, e As AsyncCompletedEventArgs)
    MsgBox("Downloaded")
End Sub

Private Function DLOAD()
    Try
        Dim WebClientT As New System.Net.WebClient()
        AddHandler WebClientT.DownloadFileCompleted, AddressOf DownloadFileCompletedD
        ByteArray = WebClientT.DownloadData("https://ip/file.filetype")
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try
End Function

Answer 1

该事件仅在您使用 "DownloadFileAsync" 时调用，因为您正在同步下载，线程将等待下载所有字节而不调用该事件。那么你不需要这个事件。完整下载将始终低于 DownloadData。

如果调用此方法使用

AddHandler WebClientT.DownloadDataCompleted, AddressOf DownloadCompleted
WebClientT.DownloadDataAsync(uri)

更多信息：

https://msdn.microsoft.com/pl-pl/library/system.net.webclient.downloadfilecompleted(v=vs.110).aspx?cs-save-lang=1&cs-lang=vb#code-snippet-2

未调用 DownloadFileCompleted 事件

DownloadFileCompleted event not being called

vb.net

network-programming

webclient