Watch Folder in VB.net/WPF

Question

I'm having a problem trying to work out how to watch a folder for changes. This is how far I've got:

Class MainWindow

<PermissionSet(SecurityAction.Demand, Name:="FullTrust")> _
Private Sub Window_Loaded(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles MyBase.Loaded
    Dim Path As String = "C:\Temp"

    ' Create a new FileSystemWatcher and set its properties.
    Dim watcher As New FileSystemWatcher()
    watcher.Path = Path
    ' Watch for changes in LastAccess and LastWrite times, and
    ' the renaming of files or directories. 
    watcher.NotifyFilter = (NotifyFilters.LastAccess Or NotifyFilters.LastWrite Or NotifyFilters.FileName Or NotifyFilters.DirectoryName)
    ' Only watch text files.
    watcher.Filter = "*.txt"

    ' Add event handlers.
    AddHandler watcher.Changed, AddressOf OnChanged
    AddHandler watcher.Created, AddressOf OnChanged
    AddHandler watcher.Deleted, AddressOf OnChanged
    AddHandler watcher.Renamed, AddressOf OnRenamed

    ' Begin watching.
    watcher.EnableRaisingEvents = True

End Sub

' Define the event handlers.
Private Shared Sub OnChanged(ByVal source As Object, ByVal e As FileSystemEventArgs)
    ' Specify what is done when a file is changed, created, or deleted.
    MsgBox("File: " & e.FullPath & " " & e.ChangeType)
End Sub

Private Shared Sub OnRenamed(ByVal source As Object, ByVal e As RenamedEventArgs)
    ' Specify what is done when a file is renamed.
    MsgBox("File: {0} renamed to {1}", e.OldFullPath, e.FullPath)
End Sub
End Class

The problem is when a change occurs in the folder the program exits with no error code. I've read a few related posts and I know it has something to do with thread safety. However I've no idea how to make this program "thread safe". Can anyone give me some advice? Thanks!

Answer 1

I'm not getting any thread safety issues here. I think the problem is:

MsgBox("File: {0} renamed to {1}", e.OldFullPath, e.FullPath)

should be

MsgBox(String.Format("File: {0} renamed to {1}", e.OldFullPath, e.FullPath))