Question Folder Monitoring issue

[Jose Cuervo]

Hi,

Right i have managed to get backgroundworking working, but it has gave me an issue when i try to add it to a program i already have lol

I have an application that monitors a folder, and when a file is created it performs some actions. I have made the actions into a background worker and it works great, for a single file. If i try to run it when mutliple files hit the folder, it crashes, as it has to archive/delete the original file, and by then the variable i am using for the file name has changed.

The only way i know how to pass my file names is to create global variable (not a great idea) But i don't know what else i can do? I been stuck at this for ages lol

Here is the code i am using which does the folder monitoring, the triggers the background worker.

    Dim sFileName As String
    Dim watcher As New FileSystemWatcher

    Private WithEvents BackgroundWorker As System.ComponentModel.BackgroundWorker

    Delegate Sub CallBackToUIThread(ByVal e As FileSystemEventArgs)

    'This is the section that watches for files being created in the directory
    Private Sub Window1_Loaded(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles MyBase.Loaded

        watcher.Path = My.Settings.folderToMonitor
        watcher.NotifyFilter = NotifyFilters.FileName

        AddHandler watcher.Created, AddressOf onChanged

        watcher.EnableRaisingEvents = True

    End Sub
    Public Sub NotifyUIThreadOfChange(ByVal e As FileSystemEventArgs)

        If e.ChangeType = WatcherChangeTypes.Created Then

            sFileName = e.FullPath
            BackgroundWorker = New System.ComponentModel.BackgroundWorker
            BackgroundWorker.WorkerReportsProgress = True
            BackgroundWorker.RunWorkerAsync()            

        End If


    End Sub

    Private Sub onChanged(ByVal source As Object, ByVal e As FileSystemEventArgs)

        'Call back to the UI thread

        Me.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Normal, New CallBackToUIThread(AddressOf NotifyUIThreadOfChange), e)

    End Sub

In my background worker i have the line "Kill(sFileName)" which is when i am using multiple file, it all goes belly up lol

I still want the UI to be free and not lock up, but just can't figure out what to do.

Please help

 

[Jose Cuervo]

Typical, when you ask you end up figuring it out! lol

Can someone give me their thoughts on my idea though?

What i done was created a new global string variable called sWorkerStatus

At the start of the background worker i set it to "Working" and at the end set it to "Free"

Then i changed the sub onChanged to have a loop in it telling it to sleep for a half second if the workerstatus is at working

    Private Sub onChanged(ByVal source As Object, ByVal e As FileSystemEventArgs)

        'Call back to the UI thread

        Do
            System.Threading.Thread.Sleep(500)
            If sWorkerStatus = "Free" Then
                Exit Do

            End If
        Loop

        Me.Dispatcher.BeginInvoke(System.Windows.Threading.DispatcherPriority.Normal, New CallBackToUIThread(AddressOf NotifyUIThreadOfChange), e)

    End Sub

Actually, typing this out, i am wondering, would i be better using backgroundworker_complete to achieve it?

 

[MattP]

onCreated should be calling BackgroundWorker.ReportProgress().

If your program that you're calling has issues with multiple files being processed maybe you should think about sending the files to a queue where they can be processed one at a time.

 

[JohnH]

You could add the paths to a Queue(Of String) and have BackgroundWorker process them, run worker if not IsBusy. Remember to SyncLock access to the queue object.