.net 2010 vb: COM interop DLL WITHEVENTS

Question

I am trying to write a COM Interop DLL that instantiates an instance of FileSystemWatcher and sets the Network folder and file name to watch for.  When the file appears in the watched folder I want the dll to raise and event "FileReady"  so the calling VBA macro will capture the event and then call some VBA macros.  "Wait_For_File" sets the path and file name. LogChange raises the event.

This is the class module.

Option Explicit On
Option Strict On
Imports System
Imports System.IO
Imports System.Diagnostics
Imports System.Runtime.InteropServices

Public Delegate Sub FileReadyDelegate(ByVal File_Path As String, ByVal File_Name As String, ByVal Msg As String, ByVal ChangeType As WaitForDirectoryChange.ChangeTypes)


<InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIDispatch)> _
Public Interface IFileReadyEvents
    <DispId(1)> _
    Sub FileReady(ByVal File_Path As String, ByVal File_Name As String, ByVal Msg As String, ByVal ChangeType As WaitForDirectoryChange.ChangeTypes)
End Interface

Public Interface IWaitForDirectoryChange
    'Subs, Functions, Properties go here 
    'No subs, functions, or events need to be declared here 
    'to make our events work properly in COM 
    Enum ChangeTypes As Integer
        All = System.IO.WatcherChangeTypes.All
        Changed = System.IO.WatcherChangeTypes.Changed
        Created = System.IO.WatcherChangeTypes.Created
        Deleted = System.IO.WatcherChangeTypes.Deleted
        Renamed = System.IO.WatcherChangeTypes.Renamed
    End Enum
End Interface

<ComSourceInterfaces(GetType(IFileReadyEvents)), ClassInterface(ClassInterfaceType.None)> _
Public Class WaitForDirectoryChange : Implements IWaitForDirectoryChange
    Public Event FileReady As FileReadyDelegate


    Enum ChangeTypes As Integer
        All = System.IO.WatcherChangeTypes.All
        Changed = System.IO.WatcherChangeTypes.Changed
        Created = System.IO.WatcherChangeTypes.Created
        Deleted = System.IO.WatcherChangeTypes.Deleted
        Renamed = System.IO.WatcherChangeTypes.Renamed
    End Enum

    Dim WatchFolder As FileSystemWatcher
    Private Property mFile_Path As String
    Private Property mFile_Name As String
    Private Property mEvent_Text As String
    Private Property mFile_Ready As Boolean = False


    Public Sub Wait_For_File(ByVal File_Path As String, ByVal File_Name As String)
        If (File_Path + File_Name) = "" Then
            Err.Raise(555, "Wait_For_File", "Wait_For_File args empty")
        End If
        If Right(File_Path, 1) = "\" Then
            mFile_Path = Left(File_Path, Len(File_Path) - 1)
        Else
            mFile_Path = File_Path
        End If
        mFile_Name = File_Name


        WatchFolder = New System.IO.FileSystemWatcher()

        WatchFolder.Path = mFile_Path
        WatchFolder.Filter = mFile_Name
        WatchFolder.NotifyFilter = IO.NotifyFilters.DirectoryName
        WatchFolder.NotifyFilter = WatchFolder.NotifyFilter Or _
                                   IO.NotifyFilters.FileName
        WatchFolder.NotifyFilter = WatchFolder.NotifyFilter Or _
                                   IO.NotifyFilters.Attributes
        WatchFolder.NotifyFilter = WatchFolder.NotifyFilter Or _
                                    IO.NotifyFilters.CreationTime

        ' add the handler to each event
        AddHandler WatchFolder.Changed, AddressOf logchange
        AddHandler WatchFolder.Created, AddressOf logchange
        AddHandler WatchFolder.Deleted, AddressOf logchange

        'Set this property to true to start watching
        WatchFolder.EnableRaisingEvents = True


    End Sub
    Private Sub logchange(ByVal source As Object, ByVal e As System.IO.FileSystemEventArgs)
        Dim WhatChanged As ChangeTypes

        If e.ChangeType = IO.WatcherChangeTypes.Changed Then
            mEvent_Text = "File " & e.FullPath & _
                                    " has been modified"
        End If
        If e.ChangeType = IO.WatcherChangeTypes.Created Then
            mEvent_Text = "File " & e.FullPath & _
                                    " has been created"
            If UCase(e.Name) = UCase(mFile_Name) Then
                WatchFolder.EnableRaisingEvents = False
                WhatChanged = CType(e.ChangeType, ChangeTypes)
                RaiseEvent FileReady(mFile_Path, mFile_Name, mEvent_Text, WhatChanged)
                Beep()
            End If
        End If
        If e.ChangeType = IO.WatcherChangeTypes.Deleted Then
            mEvent_Text = "File " & e.FullPath & _
                                    " has been deleted"
        End If

    End Sub


    Public Sub New()

    End Sub
End Class

Answer 1

Hello,

Please look at this http://stackoverflow.com/questions/24315/is-it-possible-to-raise-an-event-when-a-file-becomes-accessible which may helps.

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Think again!