File System Watcher

hugh@kmcnetwork.com · December 27th, 2003, 10:31 PM

Hello Everyone and thanks for your help in advance. I am developing an application that utilizes the FileSystemWatcher. However, I am having difficulty getting the application to determine the difference between a created file and a changed file. Here is my code:

        Dim myWatcher As New System.IO.FileSystemWatcher

        Dim myPath As String = "C:\My Documents"

        myWatcher.Path = myPath

        myWatcher.EnableRaisingEvents = True

        AddHandler myWatcher.Created, AddressOf logchange

        AddHandler myWatcher.Changed, AddressOf logchange

    Private Sub logchange(ByVal source As Object, ByVal e As System.IO.FileSystemEventArgs)

        If e.ChangeType = WatcherChangeTypes.Created Then
            Label1.Text = e.FullPath & " was created"
        ElseIf e.ChangeType = WatcherChangeTypes.Changed Then
            Label1.Text = e.FullPath & " was changed"
        End If

    End Sub

When I test this, all new files created come up as "changed" rather than created. What ami I doing wrong? Any help would be greatly appreciated. Thanks.

Imar · December 28th, 2003, 08:50 AM

Hi Hugh,

How do you test this? That is, how do you "create" your files? When you copy an existing file into the watched directory, it will indicate the file has changed. However, when you save a Word document in the folder, or choose File | New | Text Document for example, you'll see the file marked as created.

Imar

---------------------------------------
Imar Spaanjaars
Everyone is unique, except for me.

hugh@kmcnetwork.com · December 28th, 2003, 09:44 AM

Hi Imar,

I am testing it the way you mentioned, i.e., I have created new files into the directory using both Notepad and Word. I have also used "Save As" as well as copying files into the directory. However, I never return a "Created" status. Also, I tried not converting the ChangeType to string and it returns a "4" every time. Additiaionally, in another iteration of the program, I tried setting up different subroutines with different handles clause, which also did not work. Not sure what is going on.

Imar · December 28th, 2003, 10:41 AM

Really weird. I used the code you posted in an app and it works fine.

You may try to add the new text to the label, instead of overwriting the previous stuff. I found that when you save a Word document, the code fires multiple times, so you may end up with a Change for the latest event, overwriting a previous Create.

Other than that, I am stumped. It works as expected here....

Imar

---------------------------------------
Imar Spaanjaars
Everyone is unique, except for me.

hugh@kmcnetwork.com · December 28th, 2003, 11:51 AM

Imar,

What OS are you on? I am using Windows XP Pro for testing.

Imar · December 28th, 2003, 12:05 PM

Same here. Windows XP Pro, SP1.

I tried the example in Visual Studio .NET 2003.... Haven't tried 2002 yet.

Imar

---------------------------------------
Imar Spaanjaars
Everyone is unique, except for me.

hugh@kmcnetwork.com · December 28th, 2003, 12:50 PM

Imar,

As always, you have cut to the root of the problem. The problem was not in the FileSystemWatcher , but in the label structure. Since there were multiple events firing in both Notepad and Word documents, and it appears that the final event of any created file is a changed, I was only picking up changes. In any event, thanks for the help (as always).

meinken · March 8th, 2004, 02:20 PM

Why won't the following work?

<%@ Page Language="VB" Debug="True" %>
<%@ import Namespace="System.IO" %>
<%@ import Namespace="System.Diagnostics" %>
<script runat="server">

    Sub Page_Load(sender as Object, e as EventArgs)
        Dim myWatcher As New System.IO.FileSystemWatcher

        Dim myPath As String = "C:\temp"

        myWatcher.Path = myPath

        myWatcher.EnableRaisingEvents = True

        AddHandler myWatcher.Created, AddressOf logchange

        AddHandler myWatcher.Changed, AddressOf logchange

    End Sub

    Public Sub logchange(ByVal source As Object, ByVal e As System.IO.FileSystemEventArgs)
        If e.ChangeType = WatcherChangeTypes.Created Then
            Label1.Text = e.FullPath & " was created"
        ElseIf e.ChangeType = WatcherChangeTypes.Changed Then
            Label1.Text = e.FullPath & " was changed"
        End If

    End Sub

</script>
<html>
<head>
</head>
<body>
    <form runat="server">
        <asp:Label id="Label1" runat="server">Watching for changes to c:\temp...</asp:Label>
    </form>
</body>
</html>

Imar · March 8th, 2004, 02:40 PM

I guess it *does* work, but only for a split-second (a pico second, on fast or tuned systems ;) )

The Page_Load event fires when the page loads. However, as soon as the page has finished loading, all variables declared inside the method body get out of scope and are destroyed. So, only during the Page_Load event at the server will this code (technically) work.

A FileSystemWatcher is more suitable in desktop or Service applications.

Cheers,

Imar

---------------------------------------
Imar Spaanjaars
Everyone is unique, except for me.

meinken · March 9th, 2004, 09:39 AM

Okay, I understand that. Now how about this? I use no page_load event, only "clickable" events. Still no go...

<%@ Page Language="VB" Debug="True" %>
<%@ import Namespace="System.IO" %>
<%@ import Namespace="System.Diagnostics" %>
<script runat="server">

              Public watchfolder As FileSystemWatcher

              Public objFSO = Server.CreateObject("Scripting.FileSystemObject")

              Public Sub btn_start_Click(sender As Object, e As EventArgs)
                 watchfolder = New System.IO.FileSystemWatcher()

    ' if objfso.FileExists(txt_watchpath.Text) Then
                  if objfso.FolderExists(txt_watchpath.Text) Then
                    'this is the path we want to monitor
                     watchfolder.Path = txt_watchpath.Text
                     txt_folderactivity.Text &= "Monitor Started...." & vbCrLf
                     txt_folderactivity.Text &= " Watching " & txt_watchpath.Text & "...." & vbCrLf

                  'Add a list of Filter we want to specify make sure you use OR for each Filter as we need to
                  'include all of those

                     watchfolder.NotifyFilter = IO.NotifyFilters.DirectoryName
                     watchfolder.NotifyFilter = watchfolder.NotifyFilter Or IO.NotifyFilters.FileName
                     watchfolder.NotifyFilter = watchfolder.NotifyFilter Or IO.NotifyFilters.Attributes

                  ' add the handler to each event
                     AddHandler watchfolder.Changed, AddressOf logchange
                     AddHandler watchfolder.Created, AddressOf logchange
                     AddHandler watchfolder.Deleted, AddressOf logchange
                  ' add the rename handler as the signature is different
                     AddHandler watchfolder.Renamed, AddressOf logrename

                     watchfolder.IncludeSubdirectories = False
                     watchfolder.EnableRaisingEvents = True
                   'Set this property to true to start watching
                     btn_startwatch.Enabled = False
                     btn_stop.Enabled = True
                  else
                     txt_folderactivity.Text = "Invalid directory: " & txt_watchpath.Text & ". Re-enter"
                  end if
              End Sub

              Public Sub btn_stop_Click(sender As Object, e As EventArgs)
                 txt_folderactivity.Text &= "Monitor Stopped..." & vbCrLf
                 watchfolder = New System.IO.FileSystemWatcher()
                 watchfolder.EnableRaisingEvents = False
                 btn_startwatch.Enabled = True
                 btn_stop.Enabled = False
              End Sub

              Public Sub logchange(ByVal source As Object, ByVal e As System.IO.FileSystemEventArgs)
                 txt_folderactivity.Text &= "***Event Fired!***"

                 If e.ChangeType = IO.WatcherChangeTypes.Changed Then
                    txt_folderactivity.Text &= "File " & e.FullPath & " has been modified" & vbCrLf
                 End If

                 If e.ChangeType = IO.WatcherChangeTypes.Created Then
                    txt_folderactivity.Text &= "File " & e.FullPath & " has been created" & vbCrLf
                 End If

                 If e.ChangeType = IO.WatcherChangeTypes.Deleted Then
                    txt_folderactivity.Text &= "File " & e.FullPath & " has been deleted" & vbCrLf
                 End If
              End Sub

              Public Sub logrename(ByVal source As Object, ByVal e As System.IO.RenamedEventArgs)
                  txt_folderactivity.Text &= "File" & e.OldName & " has been renamed to " & e.Name & vbCrLf
              End Sub

</script>
<html>
<head>
</head>
<body>
    <form runat="server">
        <p>
                    &n bsp;       &nbs p;                 &n bsp; 
                    &n bsp;       &nbs p;                 &n bsp;       &nbs p;                 &n bsp;       &nbs p;            
                   
            <asp:Button id="btn_startwatch" onclick="btn_start_Click" runat="server" Text="Start Watching"></asp:Button>
        </p>
        <p>
            Type Folder to Watch: 
            <asp:TextBox id="txt_watchpath" runat="server" Width="323px"></asp:TextBox>
                
            <asp:Button id="btn_stop" onclick="btn_stop_Click" runat="server" Text="Stop Watching"></asp:Button>
        </p>
        <p>
            Folder Activity:
        </p>
        <p>
            <asp:TextBox id="txt_folderactivity" runat="server" Width="759px" Height="409px" TextMode="MultiLine"></asp:TextBox>
        </p>
    </form>
</body>
</html>