VB.et FileSystemWatcher 事件处理程序 - 处理程序重复调用（不需要）

问：

我正在尝试通过将文件添加到列表中的自定义类来使用 FileSystemWatch 类记录目录中的文件活动，不幸的是，似乎在复制文件或将新文件添加到目标目录时，它运行了 4 次而不是一次。

将文件添加到目录时，AddressOf Sub 将写入 3 到 4 次，而不是只写入一次。我不知道为什么。

下面是代码片段。

Public fileTypefilter As String = "*.xlsx"
Public DesDir As String = "C:\"
Public EventLog As List(Of FileEvent)
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    Dim watchDir As String = DesDir
    Dim watch As New FileSystemWatcher(watchDir)
    Me.Text = "Monitoring " & watch.Path

    watch.IncludeSubdirectories = false
    watch.Filter = "*.xlsx"

    AddHandler watch.Changed, AddressOf watch_Changed

    watch.EnableRaisingEvents = True
End Sub

Private Sub watch_Changed(ByVal sender As Object, ByVal e As FileSystemEventArgs)

    Try
        EventLog.Add(New FileEvent(e.FullPath))
        Exit Sub
    Catch ex As NullReferenceException
        EventLog = New List(Of FileEvent)({New FileEvent(e.FullPath)})
        Exit Sub
    End Try


End Sub