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我正在制作一个自动文件下载器，当我按下按钮时，我需要它重新下载并覆盖文件，但我不希望它在下载时挂起。我不知道如何为此代码实现 DownloadFileAsync。请帮忙！

这是我的代码：

 Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Button1.Enabled = False
        Button1.Text = "Updating..."
        WebBrowser1.Visible = True
        My.Computer.Network.DownloadFile _
          (address:="http://199.91.154.170/e9f6poiwfocg/pei02c8727sa720/Ultra+v08.zip", _
          destinationFileName:=Path.Combine(Environment.GetFolderPath( _
          Environment.SpecialFolder.ApplicationData), _
          "test/Test.zip"), _
          userName:=String.Empty, password:=String.Empty, _
          showUI:=False, connectionTimeout:=100000, _
          overwrite:=True)
        WebBrowser1.Visible = False
        Button1.Text = "Updated!"
        PictureBox1.Visible = True

    End Sub

提前致谢！

4

1 回答 1

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您可以使用System.Net.WebClient以异步模式下载文件。

示例代码：

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim client As New WebClient()
    AddHandler client.DownloadProgressChanged, AddressOf ShowDownloadProgress
    AddHandler client.DownloadFileCompleted, AddressOf OnDownloadComplete
    client.DownloadFileAsync(New Uri("http://199.91.154.170/e9f6poiwfocg/pei02c8727sa720/Ultra v08.zip"), "test/Test.zip")


End Sub

Private Sub OnDownloadComplete(ByVal sender As Object, ByVal e As AsyncCompletedEventArgs)
    If Not e.Cancelled AndAlso e.Error Is Nothing Then
        MessageBox.Show("DOwnload success")
    Else
        MessageBox.Show("Download failed")
    End If
End Sub

Private Sub ShowDownloadProgress(ByVal sender As Object, ByVal e As DownloadProgressChangedEventArgs)
    ProgressBar1.Value = e.ProgressPercentage
End Sub
于 2013-03-11T14:55:15.493 回答