一个关于FileSystemWatcher的问题，谢谢

Hi,大家好，我在用FileSystemWatcher监视某个目录的时候出现了问题，在往被监视的目录拷贝文件的时候Create事件似乎不能被触发（请看下面的程序），我把一个txt文件从C盘的根目录拷贝到C:\ABC目录下，但是并没有触发事件，弹出消息框，请问是怎么回事，谢谢！
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    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim watcher As New FileSystemWatcher
        watcher.Path = "C:\ABC"
        watcher.NotifyFilter = (NotifyFilters.Attributes Or NotifyFilters.LastAccess Or NotifyFilters.LastWrite Or NotifyFilters.CreationTime Or NotifyFilters.Size)
        watcher.Filter = "*.txt"
        AddHandler watcher.Created, AddressOf OnChanged
        'AddHandler watcher.Changed, AddressOf OnChanged
        'AddHandler watcher.Deleted, AddressOf OnChanged
        'AddHandler watcher.Renamed, AddressOf OnRenamed
        watcher.EnableRaisingEvents = True
    End Sub

    Sub OnChanged(ByVal sender As Object, ByVal e As FileSystemEventArgs)
        MessageBox.Show("test")
    End Sub --------------------编程问答-------------------- 啊？CSDN现在人气这么差啊？都没有关注一下？ --------------------编程问答--------------------      Dim   watcher   As   New   FileSystemWatcher
这是函数内部变量，随着函数的结束，而被回收了
把它定义为类变量
--------------------编程问答-------------------- http://topic.csdn.net/u/20071216/11/a79d510d-195d-43bc-b92a-bf5dbf72ad31.html --------------------编程问答-------------------- http://topic.csdn.net/u/20071216/11/a79d510d-195d-43bc-b92a-bf5dbf72ad31.html --------------------编程问答-------------------- 谢谢hdt的回复

现在我将程序修改为：
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Public watcher As FileSystemWatcher
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        watcher = New FileSystemWatcher
        watcher.Path = "C:\ABC"
        watcher.NotifyFilter = (NotifyFilters.Attributes Or NotifyFilters.LastAccess Or NotifyFilters.LastWrite Or NotifyFilters.CreationTime Or NotifyFilters.Size)
        watcher.Filter = "*.txt"
        AddHandler watcher.Created, AddressOf OnChanged
        'AddHandler watcher.Changed, AddressOf OnChanged
        'AddHandler watcher.Deleted, AddressOf OnChanged
        'AddHandler watcher.Renamed, AddressOf OnRenamed
        watcher.EnableRaisingEvents = True
    End Sub

    Sub OnChanged(ByVal sender As Object, ByVal e As FileSystemEventArgs)
        MessageBox.Show("test")
    End Sub
---------------------
但是还是没有反应，messagebox还是不出来 --------------------编程问答-------------------- 我又试了一下，按照MSDN上写控制台程序就可以，但是现在我需要用窗体程序啊。请问怎么解决

补充：.NET技术 ,  C#