如何覆盖下载的文件 vb.net
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How to overwrite downloaded file vb.net
提问by TheCreepySheep
I'm making a automatic file downloader and I need it to redownload and overwrite the file, when i press the button.
我正在制作一个自动文件下载器，当我按下按钮时，我需要它来重新下载和覆盖文件。
Here is my code:
这是我的代码：
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
My.Computer.Network.DownloadFile _
("http://www.randomurl.com/randomfile.txt", _
Path.Combine(Environment.GetFolderPath( _
Environment.SpecialFolder.ApplicationData), _
"test/randomfile.txt"))
End Sub
回答by Steve
There is an overload for DownloadFilethat allows the overwrite of the previous file
DownloadFile有一个重载，允许覆盖以前的文件
My.Computer.Network.DownloadFile
(address, destinationFileName, userName,
password, showUI, connectionTimeout, overwrite)
As from MSDN
来自 MSDN
- address = String or Uri. Path of the file to download, including file name and host address. Required.
- destinationFileName = String. File name and path of the downloaded file. Required.
- userName = String. User name to authenticate. Default is an empty string, "".
- password = String.Password to authenticate. Default is an empty string, "".
- showUI = Boolean.Specifies whether to display the progress of the operation. Default is False.
- connectionTimeout = Int32. Timeout interval, in milliseconds. Default is 100 seconds.
- overwrite = Boolean. Specifies whether to overwrite existing files. Default is False.
- 地址 = 字符串或 Uri。要下载的文件的路径，包括文件名和主机地址。必需的。
- 目标文件名 = 字符串。下载文件的文件名和路径。必需的。
- 用户名 = 字符串。要验证的用户名。默认为空字符串“”。
- 密码 = String.Password 进行身份验证。默认为空字符串“”。
- showUI = Boolean.指定是否显示操作进度。默认值为假。
- 连接超时 = Int32。超时间隔，以毫秒为单位。默认值为 100 秒。
- 覆盖 = 布尔值。指定是否覆盖现有文件。默认值为假。
Thus you could change your code in this way
因此，您可以通过这种方式更改代码
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
My.Computer.Network.DownloadFile _
(address := "http://www.randomurl.com/randomfile.txt", _
destinationFileName := Path.Combine(Environment.GetFolderPath( _
Environment.SpecialFolder.ApplicationData), _
"test/randomfile.txt"), _
userName := string.Empty, password := string.Empty, _
showUI := False, connectionTimeout := 100000, _
overwrite := True)
End Sub
回答by GojiraDeMonstah
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
Dim uri As System.Uri = New System.Uri("http://www.randomurl.com/randomfile.txt")
Dim webclient As System.Net.WebClient = New System.Net.WebClient()
Dim path As String = New String(System.IO.Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "test\randomfile.txt"))
Dim fileInfo As System.IO.FileInfo = New System.IO.FileInfo(path)
If Not System.IO.Directory.Exists(fileInfo.Directory.FullName) Then
System.IO.Directory.CreateDirectory(fileInfo.Directory.FullName)
End If
AddHandler webclient.DownloadFileCompleted, AddressOf webclient_DownloadDataCompleted
webclient.DownloadFileAsync(uri, path)
End Sub
Private Sub webclient_DownloadDataCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.AsyncCompletedEventArgs)
MessageBox.Show("Your download has completed.")
End Sub
(EDIT - changed to show async method as requested in comments)
（编辑 - 更改为按照评论中的要求显示异步方法）
Note that the file will be overwritten if it exists -> http://msdn.microsoft.com/en-us/library/ez801hhe(v=VS.80).aspx
请注意，如果该文件存在，则该文件将被覆盖 -> http://msdn.microsoft.com/en-us/library/ez801hhe(v=VS.80).aspx
