Vb.net WebClient.DownloadFileAsync在XP不會工作和8.1

您好我在做一個vb.net更新功能，讓我的用戶的通知，當有新的更新可供下載Vb.net WebClient.DownloadFileAsync在XP不會工作和8.1

所以它贏的所有作品8和7，但是當我嘗試在XP和8.1運行它，它只是提供了一個下載完成，但不下載任何文件：■

這裏是我的代碼：

Imports System.Net 

Public Class Form5 
    Private Sub LogInButton1_Click(sender As Object, e As EventArgs) Handles LogInButton1.Click 
     Dim client As WebClient = New WebClient 
     AddHandler client.DownloadProgressChanged, AddressOf client_ProgressChanged 
     AddHandler client.DownloadFileCompleted, AddressOf client_DownloadCompleted 
     client.DownloadFileAsync(New Uri("FILE the download"), "C:\users\" & System.Environment.UserName & _ 
           "\AppData\Local\Software_update.exe") 
     LogInButton1.Text = "Download in Progress" 
     LogInButton1.Enabled = False 
    End Sub 

    Private Sub client_ProgressChanged(ByVal sender As Object, ByVal e As DownloadProgressChangedEventArgs) 
     Dim bytesIn As Double = Double.Parse(e.BytesReceived.ToString()) 
     Dim totalBytes As Double = Double.Parse(e.TotalBytesToReceive.ToString()) 
     Dim percentage As Double = bytesIn/totalBytes * 100 

     LogInProgressBar1.Value = Int32.Parse(Math.Truncate(percentage).ToString()) 
    End Sub 

    Private Sub client_DownloadCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.AsyncCompletedEventArgs) 
     MessageBox.Show("Download Complete please restart the app ") 
     LogInButton1.Text = "Download Complete" 
    End Sub 

    Private Sub Form5_FormClosing(sender As Object, e As FormClosingEventArgs) Handles MyBase.FormClosing 
     Form1.Close() 
    End Sub 
End Class

注意我力又上測試該Vista

來源

2014-09-29 Nicolai

幾乎可以肯定的異常被拋出d

。該異常通過'DownloadCompleted'事件處理程序中的'e.Error'屬性提供給您。看看它，它會告訴你出了什麼問題。你真的應該知道這一點，因爲你應該閱讀'WebClient'類的文檔和你正在使用的成員。 – jmcilhinney 2014-09-30 00:02:04

我已經解決問題，問題是，AppData文件夾是每個操作系統的不同：我用這個來修復它

Dim appData As String = GetFolderPath(SpecialFolder.ApplicationData) 


client.DownloadFileAsync(New Uri("FILE_URL"), appData & "\Software_update.exe")

來源

2014-10-01 09:16:36 Nicolai

Vb.net WebClient.DownloadFileAsync在XP不會工作和8.1

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