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Using Delegates for Cross-thread operations

Posted on 2008-10-13
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Last Modified: 2012-06-21
I need some help understanding the use of Delegates. I would like to have a listbox on the main form and be able to add to it from other threads. Below is some example code that I've been playing with but not very successfully. Can someone point out what I'm doing wrong? I keep getting "Cross-thread operation not valid". Thanks!
Public Class One
    Private Delegate Sub Logger(ByVal _message As String)
    Dim t As Threading.Thread
    Dim WithEvents oTwo As New Two
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        t = New Threading.Thread(AddressOf oTwo.startCounting)
        t.Start()
    End Sub
    Private Sub updateList(ByVal entry As String)
        ListBox1.Items.Add(entry)
    End Sub
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        t.Abort()
    End Sub
    Sub ThreadLogging(ByVal entry As String) Handles oTwo.LogUpdated
        Invoke(New Logger(AddressOf updateList), entry)
        Dim writer As Logger
        writer = AddressOf updateList
        writer.Invoke(entry)
    End Sub
End Class
 
Public Class Two
    Public Event LogUpdated(ByVal entry As String)
 
    Public Sub startCounting()
        Dim count As Integer = 0
        While True
            WriteMonitorLog(count.ToString)
            count += 1
            Threading.Thread.Sleep(100)
        End While
    End Sub
    Private Sub WriteMonitorLog(ByVal entry As String)
        RaiseEvent LogUpdated(entry)
    End Sub
End Class

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Question by:Tharo_Systems
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crazyman earned 2000 total points
ID: 22703457
change this

Sub ThreadLogging(ByVal entry As String) Handles oTwo.LogUpdated
        Invoke(New Logger(AddressOf updateList), entry)
            End Sub
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Author Comment

by:Tharo_Systems
ID: 22703501
I knew it had to be something simple! Thanks so much!
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