複製文件在修改FIleSystemWatcher，Visual Basic（VS 2012 V11）

Question

通過瀏覽很多網站和一些教程視頻後，我仍然難住這一個。我正在完成一個程序，我需要添加最後一個功能。

程序以這種方式工作。用戶在文本框1中指定一個文件，然後在文本框2中指定一個目錄。用戶通過複製到文本框3來設置他們想要文件的頻率。用戶點擊運行，程序將文件複製到新位置，每次複製文件名時都會添加一個數字（以避免覆蓋）。這一切都可以正常工作，但我希望用戶可以選擇按時間複製文件或修改文件。

如何使用FileSystemWatcher查找目錄中的修改（在textbox1中給出），然後調用將指定目錄複製到目標目標（在文本框2中指定）的語句？

附加註釋：

在一個教程FileSystemWatcher的路徑通過這樣做

Dim watched As String = System.IO.Path.Combine(Environment.GetEnvironmentVariable("USERPROFILE"), "Pictures") 
     Dim fsw As New FileSystemWatcher(watched) 

，該代碼指示所述的路徑設置爲「C：\用戶[用戶名] \圖片」 。 我無法在網上找到顯示變量「.GetEnvironmentVariable」接受的變量，甚至變量的含義。這是我最後一位代碼遇到問題的很多原因之一。

Answer 1

GetEnvironmentVariable返回當前進程指定環境的值。

在您的示例中，USERPROFILE是當前用戶的文件夾路徑。例如，在我的筆記本電腦上USERPROFILE是C：\ Users \ Tim。

System.IO.Path.Combine(Environment.GetEnvironmentVariable("USERPROFILE"), "Pictures")的輸出將是USERPROFILE路徑加上「圖片」 - 繼續我的示例，它將是C:\Users\Tim\Pictures - 這是我的用戶帳戶的「我的圖片」文件夾的物理路徑。

要獲得所有環境變量的列表，如果您好奇，請轉到DOS提示符並鍵入SET並點擊返回。

要回答你的原問題，你需要處理FileSystemWatcher.Changed Event。

例如：

Private Shared Sub OnChanged(source As Object, e As RenamedEventArgs) 

    ' Do your copy here 
End Sub 

您可以掛鉤的事件處理程序到你的FileWatcher這樣的：

AddHandler fsw.Changed, AddressOf OnChanged 

然而，要注意從MSDN文檔此警告。

Common file system operations might raise more than one event. For example, when a file is moved from one directory to another, several OnChanged and some OnCreated and OnDeleted events might be raised. Moving a file is a complex operation that consists of multiple simple operations, therefore raising multiple events. Likewise, some applications (for example, antivirus software) might cause additional file system events that are detected by FileSystemWatcher.

Answer 2

這是我用它做什麼，我希望它的代碼。

Option Explicit On 
Option Strict On 
Imports System.IO 
Imports Microsoft.VisualBasic ' I don't know this one, but the code worked without this. 
Imports System.Security.Permissions ' I don't know the exactly what this does but the 
    ' http://msdn.microsoft.com/ site did this, I assume it'f to allow for permission to 
    ' watch files? The code still worked for me without this 

Public Class Form1 

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Me.Load 

     Dim directoryPath As String = Path.GetDirectoryName(TextBox1.Text) 
     Dim varFileSystemWatcher As New FileSystemWatcher() 
     varFileSystemWatcher.Path = directoryPath 

     varFileSystemWatcher.NotifyFilter = (NotifyFilters.LastWrite) 

     varFileSystemWatcher.Filter = Path.GetFileName(TextBox1.Text) ' I know this 
      ' limits what's being watched to one file, but right now this is 
      ' what I want the program to do. 

     AddHandler varFileSystemWatcher.Changed, AddressOf OnChanged 


     varFileSystemWatcher.EnableRaisingEvents = True 


    End Sub 

    Private Sub OnChanged(source As Object, ByVal e As FileSystemEventArgs) 

     My.Computer.FileSystem.CopyFile(e.FullPath, TextBox2.Text & "\" & e.Name, True) 

    End Sub