Cross-thread operation not valid

[jamesd0142]

Hi again,

Im using vb 2005

Im using this code to watch a folder and log any changes etc...

[code=vbnet]
Imports System.IO
Imports System.Diagnost ics


Public Class Form1

Public watchfolder As FileSystemWatch er


Private Sub btn_startwatch_ Click(ByVal sender As System.Object, ByVal e As System.EventArg s) Handles btn_startwatch. Click
watchfolder = New System.IO.FileS ystemWatcher()

'this is the path we want to monitor
watchfolder.Pat h = txt_watchpath.T ext

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

watchfolder.Not ifyFilter = IO.NotifyFilter s.DirectoryName
watchfolder.Not ifyFilter = watchfolder.Not ifyFilter Or _
IO.NotifyFilter s.FileName
watchfolder.Not ifyFilter = watchfolder.Not ifyFilter Or _
IO.NotifyFilter s.Attributes

' add the handler to each event
AddHandler watchfolder.Cha nged, AddressOf logchange
AddHandler watchfolder.Cre ated, AddressOf logchange
AddHandler watchfolder.Del eted, AddressOf logchange

' add the rename handler as the signature is different
AddHandler watchfolder.Ren amed, AddressOf logrename

'Set this property to true to start watching
watchfolder.Ena bleRaisingEvent s = True

btn_startwatch. Enabled = False
btn_stop.Enable d = True

'End of code for btn_start_click

End Sub

Private Sub logchange(ByVal source As Object, ByVal e As _
System.IO.FileS ystemEventArgs)
If e.ChangeType = IO.WatcherChang eTypes.Changed Then
txt_folderactiv ity.Text &= "File " & e.FullPath & _
" has been modified" & vbCrLf
End If
If e.ChangeType = IO.WatcherChang eTypes.Created Then
txt_folderactiv ity.Text &= "File " & e.FullPath & _
" has been created" & vbCrLf
End If
If e.ChangeType = IO.WatcherChang eTypes.Deleted Then
txt_folderactiv ity.Text &= "File " & e.FullPath & _
" has been deleted" & vbCrLf
End If
End Sub
Public Sub logrename(ByVal source As Object, ByVal e As _
System.IO.Renam edEventArgs)
txt_folderactiv ity.Text &= "File" & e.OldName & _
" has been renamed to " & e.Name & vbCrLf
End Sub

Private Sub btn_stop_Click( ByVal sender As System.Object, ByVal e As System.EventArg s) Handles btn_stop.Click
' Stop watching the folder
watchfolder.Ena bleRaisingEvent s = False
btn_startwatch. Enabled = True
btn_stop.Enable d = False

End Sub
End Class

[/code]

I get this error: on line: 47
[code=text]
Cross-thread operation not valid: Control 'txt_folderacti vity' accessed from a thread other than the thread it was created on.
[/code]

Can anyone suggest anything, or tell me what this error means?

James

[jjvainav]

The FileSystemWatch er runs on a seperate thread, when you try to set the value of your TextBox .NET doesn't allow you to access the control from another thread, and will throw the exception you just specified.

What you need to do is call back to the main thread that your UI is running on. Here is an example on how you can accomplish this.

[CODE=vbnet]
Private Delegate Sub FileWatcherCall back(ByVal e As FileSystemEvent Args)

Private Sub logchange(ByVal source As Object, ByVal e As FileSystemEvent Args)
If txt_folderactiv ity.InvokeRequi red Then
txt_folderactiv ity.Invoke(New FileWatcherCall back(AddressOf HandleFileWatch erEvent), e)
End If
End Sub

Private Sub HandleFileWatch erEvent(ByVal e As FileSystemEvent Args)
txt_folderactiv ity.Text &= "File " & e.FullPath & " has been modified" & vbCrLf
End Sub
[/CODE]

Hope this helps.

[jamesd0142]

Thanks for the reply!

I'm affraid i don't understand, it's a little to complicated for me... Dont think I've done anything like this before.

so instead i did this:
[code=vbnet]
System.Windows. Forms.Control.C heckForIllegalC rossThreadCalls = false
[/code]
It made the problem go away.

James

[Plater]

This is an example page that should help you understand a little bit better.

http://msdn2.microsoft.com/en-us/library/ms171728.aspx