Program terminates without exception details

Question

Hi,

After dealing with the pain-in-the-____ error "The path is not on a legal form" witch only occured after dragging a file system watcher onto the form, by creating the file watcher in the code. When an event is raised, i have to tell the user what happened. I can do this using messageboxes, without any problem. But, when I wanted the output to be displayed in a textbox, the program terminates without any warning.
Here is what my code looks like:

Public Class Form1
    Public watchfolder As FileSystemWatcher
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        watchfolder = New System.IO.FileSystemWatcher()

        watchfolder.Path = "c:\temp"


        watchfolder.NotifyFilter = IO.NotifyFilters.DirectoryName
        watchfolder.NotifyFilter = watchfolder.NotifyFilter Or _
                                   IO.NotifyFilters.FileName
        watchfolder.NotifyFilter = watchfolder.NotifyFilter Or _
                                   IO.NotifyFilters.Attributes
        watchfolder.Filter = "*.*"

        AddHandler watchfolder.Changed, AddressOf logchange
        AddHandler watchfolder.Created, AddressOf logchange
        AddHandler watchfolder.Deleted, AddressOf logchange

        AddHandler watchfolder.Renamed, AddressOf logrename

        watchfolder.EnableRaisingEvents = True

        TextBox1.Text = "Changelogging started."
    End Sub
    Private Sub logchange(ByVal source As Object, ByVal e As  _
                        System.IO.FileSystemEventArgs)

        If e.ChangeType = IO.WatcherChangeTypes.Changed Then
            MsgBox("Item Updated: " & e.FullPath)
        End If
        If e.ChangeType = IO.WatcherChangeTypes.Created Then
            TextBox1.Text &= "Item Created"
        End If
        If e.ChangeType = IO.WatcherChangeTypes.Deleted Then
            MsgBox("Item Deleted: " & e.FullPath)
        End If

'code above works perfectly well, unlike the code below

    End Sub
    Public Sub logrename(ByVal source As Object, ByVal e As  _
                            System.IO.RenamedEventArgs)
        TextBox1.Text &= "File" & e.OldName & _
        " has been renamed to " & e.Name & vbCrLf
e.Name)
    End Sub
End Class

I have no clue on how to fix this, also because i don't get an error or any output from VS

Thanks in advance, Brecht

Answer 1

Hi BDrecht,
As a general solution to your problem, i suggest you wrap the code contents inside try catch block. From your code i inferred that you didn't used Try ,catch blocks at all as result it is hard for the compiler to catch exception if there is any.

Regards,
A.Murugan

Answer 2

Hi Brecht,

You can't update a control in another thread other than the thread of creating it.

Please refer http://msdn.microsoft.com/en-us/library/ms171728.aspx#Y1096 for details.

 

I definitely agree what Tech Murugan said, it is a good idea to have a try catch for debug use.

 

BTW, I updated your code of Rename and it works now FYI:

 Delegate Sub SetTextCallback([text] As String)

 Private Sub SetText(ByVal [text] As String)
  ' InvokeRequired required compares the thread ID of the
  ' calling thread to the thread ID of the creating thread.
  ' If these threads are different, it returns true.
  If Me.TextBox1.InvokeRequired Then
   Dim d As New SetTextCallback(AddressOf SetText)
   Me.Invoke(d, New Object() {[text]})
  Else
   Me.TextBox1.Text &= [text]
  End If
 End Sub

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