Working with Objects

I've been learning about watching for file creation; using FileSystemWatcher, and during part of the OnCreated process I'm trying to update a multi-line text box with what was read from the created text file.  The issue is that the text box doesn't update.

I've attached the code that I'm using.  How do I setup the objects so that I can pass the text read from the created file into the text box?  This is all on a single form.
Imports System.IO
Imports System.Security.Permissions
Imports System.Text.RegularExpressions

Public Class Form1
    Private Shared re As New Regex("[\x00-\x1F\x7F-\xFF]+", RegexOptions.Compiled)

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        TextBox1.Text = "does this work"
        Run()
    End Sub

    <PermissionSet(SecurityAction.Demand, Name:="FullTrust")> _
    Private Shared Sub Run()

        Dim watcher As New FileSystemWatcher()
        watcher.Path = "C:\Programming"
        watcher.NotifyFilter = NotifyFilters.FileName And Not NotifyFilters.Attributes
        watcher.Filter = "*.txt"
        watcher.IncludeSubdirectories = False

        AddHandler watcher.Created, AddressOf OnCreated

        watcher.EnableRaisingEvents = True


    End Sub

    Public Shared Sub OnCreated(ByVal source As Object, ByVal e As FileSystemEventArgs)
        Dim ex As Exception
        Dim strContents As String
        Dim objReader As StreamReader

        Try
            System.Threading.Thread.Sleep(1000)
            File.Move(e.FullPath, "C:\Programming\Archive\" & Replace(TimeOfDay, ":", "") & ".txt")

            Try
                objReader = New StreamReader("C:\Programming\Archive\" & Replace(TimeOfDay, ":", "") & ".txt")
                strContents = objReader.ReadToEnd()
                objReader.Close()
                strContents = re.Replace(strContents, "")
                MsgBox((strContents))
                '######################################################
                '########UNABLE TO SET TEXT BOX VALUE##################
                '######################################################
                Form1.TextBox1.Text = "yes this works"
            Catch Ex2 As Exception
                MsgBox(Ex2.Message)
            End Try
        Catch ex
            Dim typeValue As String
            typeValue = e.ChangeType.ToString
            MsgBox("ChangeType: " & typeValue)
        End Try
    End Sub

End Class

Open in new window

LVL 1
vbNewbie2009Asked:
Who is Participating?
 
Hawkvalley1Connect With a Mentor Commented:
This is because your watcher is on a diff thread and you need a delegate to talk to the textbox.

Private Delegate Sub UpdateTextDelegate(ByVal txt As String)

Private Sub UpdateText(ByVal txt As String)
    textbox1.Text = txt
End Sub

Public Sub OnCreated(ByVal source As Object, ByVal e As FileSystemEventArgs)
    textbox1.Invoke(New UpdateTextDelegate(AddressOf UpdateText), e.Name)
End Sub
0
 
ZhaolaiCommented:
It is:

Me.TextBox1.Text = "yes this works"

or just

TextBox1.Text = "yes this works"

0
 
vbNewbie2009Author Commented:
When I try using TextBox1.Text = "yes this works" ...i get a compile error referencing the following:

Cannot refer to an instance member of a class from within a shared method or shared member initializer without an explicit instance of the class
0
The 14th Annual Expert Award Winners

The results are in! Meet the top members of our 2017 Expert Awards. Congratulations to all who qualified!

 
ZhaolaiCommented:
What would happen if you remove Shared from both sub Run and sub OnCreated?

0
 
vbNewbie2009Author Commented:
I receive an exception:
"Cross-thread operation not valid:  Control 'TextBox1' accessed from a thread other than the thread it was created on.
0
 
ZhaolaiConnect With a Mentor Commented:
After you created FileSystemWatcher object, add the following line,

 watcher.SynchronizingObject = Me

0
 
vbNewbie2009Author Commented:
Thanks for the suggestions; i'll be trying these out tomorrow.
0
 
vbNewbie2009Author Commented:
Comments from Zhaolai and Hawkvalley1 each worked to populate the text object.  

Documentation link by emoreau is an excellent resource!

Thanks to all!
0
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

All Courses

From novice to tech pro — start learning today.